EPA-680/4-75-008
JULY 1975
                                       Environmental Monitoring Series
                       MONITORING  DISPOSAL-WELL
                                                 SYSTEMS
                                    ENVIRONMENTAL MONITORING AND SUPPORT
                                               LABORATORY-LAS VEGAS
                                     US. ENVIRONMENTAL PROTECTION AGENCY
                                              LAS VEGAS, NEVADA 89114

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                         RESEARCH REPORTING SERIES
Research reports of the Office of Research and Development, Environmental Protection
Agency, have been grouped Into five series.  These five broad categories were esta-
blished to facilitate further development and application of environmental technology.
Elimination of traditional grouping was consciously planned to foster technology trans-
fer and a maximum interface in related fields. The five series are:
     J.  Environmental Health Effects Research

     2.  Environmental Protection Technology
     3.  Ecological  Research

     4.  Environmental Monitoring

     5.  Socioeconomic Environmental Series.

This  report has been assigned to the ENVIRONMENTAL MONITORING series.  This
series describes research conducted to develop new or improved methods and instru-
mentation for the identification and quantification of environmental pollutants at the
lowest conceivably significant concentrations.  It also includes studies to determine
the ambient  concentrations of pollutants in the environment and/or the variance of
pollutants as a function of time or meteorological  factors.
                                  EPA REVIEW

This report has been reviewed by the Office of Research and Development, EPA,  and
approved for publication.  Approval does not signify that the contents necessarily re-
flect the views and policies of the Environmental Protection Agency, nor does mention
of trade names or commercial products constitute endorsement or recommendation for use.

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                                                                      p
                                            EPA-680/4-74-008
                                            July 1975
          MONITORING DISPOSAL-WELL SYSTEMS
                          by

                     Don L. Warner
               Consulting Geological Engineer
                 Contract No. 68-01-0759
                    ROAP No. 22AAE
               Program Element No.  1HA326
                    Project Officer

                   George B.  Morgan
    Monitoring Systems Research and Development Division
       Environmental Monitoring  and Support Laboratory
                   Las Vegas/ Nevada

ENVIRONMENTAL MONITORING AND SUPPORT LABORATORY
        OFFICE OF RESEARCH AND DEVELOPMENT
      U.S. ENVIRONMENTAL PROTECTION AGENCY
              LAS VEGAS, NEVADA  89114

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Effective June 29,  1975 the National Environmental Research Center-
Las Vegas "NERC-LV" was designated the Environmental Monitoring
and Support Laboratory-Las Vegas "EMSl-LV!1   This Laboratory is one
of three Environmental  Monitoring and Support Laboratories of the Office
of Monitoring and Technical Support in the U.S. Environmental Protec-
tion Agency's Office of Research and Development.
                           It

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                              ABSTRACT
   The U.S. Environmental Protection Agency is required, under P.L.
92-500, the Federal Water  Pollution Control Act Amendments of 1972,
to establish a system for the surveillance of the quality of the nation's
surface and ground waters.  Enactment of P. L.  93-523, the Safe Drink-
ing Water Act,  further requires that State programs in order to be ap-
proved, shall include monitoring programs to prevent underground in-
jection which endangers drinking water sources.  This report provides
information concerning the data needed for monitoring the subsurface
injection of wastewater through casedJ^p^alj^ls^a.ndjdiBcuBBes  the
methods and tools available for obtaining  the data.  The procedures for
using the data for predicting the response of the receiving aquifer to in-
jection are then outlined.  Surveillance of  operating disposal wells is re-
viewed.  Numerous examples are given throughout the text.

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                        ACKNOWLEDGMENTS
   Mr. Charles F. Meyer, Dr. Richard M. Tinlin,  and the late Dr.
Stephen Enke of General Electric—TEMPO were responsible for man-
agement and technical guidance of the project under which this report
was prepared.

   The following officials were responsible for administration and tech-
nical guidance of the project for the Environmental Protection Agency:
        Office of Research and Development (Program Area Management)

              Dr. Henry F. Enos
              Mr. John D. Koutsandreas
        NERC—Las Vegas (Program Element Direction)
              Mr. George B. Morgan
              Mr. Edward A. Schuck
              Mr. Leslie G. McMillion
              Mr. Donald B. Gilmore
                                 iv

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                           TABLE OF CONTENTS
                                                                        EL

ABSTRACT                                                             ?ii
ACKNOWLEDGMENTS                                                  5v

LIST OF ILLUSTRATIONS                                                v11

LIST OF TABLES                                                          x
SECTION I - CONCLUSIONS                                             ]
SECTION II - RECOMMENDATIONS                                       2

SECTION III - INTRODUCTION                                           3
SECTION IV - THE SUBSURFACE ENVIRONMENT                            5
            Stratigraphic Geology                                         5
            Structural Geology                                         ^
            Uthology                                                  ] J
            Fluids                                                     W
            Mechanical Properties of Injection and Confining. Units           22
            Hydrodynamics                                             29
            Resources                                                  30
SECTION V - ACQUISITION OF SUBSURFACE DATA                       32
            Prior to Drilling                                            32
            During Well Construction and Testing                          32
                   Rock samples                                        32
                   Formation fluids                                     35
                   Borehole geophysical logs                             38
                   Testing of injection and confining units                 44
                   Drill stem testing                                    45
                   Injectivlty tests                                     49

 SECTION VI - PREDICTION OF AQUIFER RESPONSE                       53

             Flow Theory                                               53
             Regional Flow                                             %>
             Pr««ur« Effect* of Injection                                  57
             Rate and Direction of Fluid Movement                         64

                                                             (continued)

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CONTENTS - Continued

                                                                    Page

            Hydraulic Fracturing^                                       68
            Generation of Earthquakes                                   70

SECTION VII - SURVEILLANCE OF OPERATING WELLS                     72

            Injection Well  Monitoring                                   72
            Periodic Inspection and Testing                               76
            Monitoring Wells                                           85
            Other Monitoring  Methods                                   88

SECTION VIII - REFERENCES                                           91

APPENDIX - EPA  POSITION ON SUBSURFACE EMPLACEMENT
            OF FLUIDS                                               97
                                     vi

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                             LIST OF ILLUSTRATIONS
Figure No.                            Title
      1          Generalized columnar section of Cambrian and
                Ordovician  strata in northeastern Illinois.                       6
      2          Isopach map of Mt. Simon Formation in northeastern
                Illinois.                                                       7
      3          Schematic east-west section of the Eau Claire and
                equivalent Rome strata.                                        8
      4          Lithologic ratio map of post-Mt. Simon pre-Knox
                rocks.                                                         9
      5          East-west cross section of Paleozoic rocks in the
                northern Ohio River Valley.                                    10
      6          Map of the  Ohio River basin and vicinity showing
                some major structural geologic features.                         12
      7          Structure on top of Mt. Simon Formation.                       13

      8         Isocon map, showing the dissolved solids content in
                parts per million of water in the upper 100 feet of the
                Mt. Simon Formation in Illinois.                               15
      9          Water  viscosity as a function of temperature and
                salinity.                                                      17
     10         Specific gravity of distilled water as a function of
                temperature.                                                  18
     11          Specific volume of water as a function of temperature
                and pressure.                                                  18
     12          Specific gravity of formation waters (Dw) versus total
                dissolved solids.                                               19
     13         Relationship between relative density and dissolved
                solids content of brines in deep aquifers of the Illinois
                basin.                                                         20
     14         Hydraulic pressure gradient in a column of water.               21

     15         Compressibility of water.                                       23

                                                               (continued)
                                        • •
                                       VII

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ILLUSTRATIONS - Continued
                                                                               je
Figure No*
     16         Map showing distribution of the average porosity of
                the Mt. Simon Formation in Illinois.                           24
     17         Reproduction of portfolio map No.  10, American Asso-
                ciation of Petroleum Geologists Geothermal Survey of
                North America.                                              28
     18         Potentiometric surface of the  Mt. Simon Formation in
                Ohio and vicinity.                                            30

      19         Sample log.                                                  33
      20          Fluid passage diagram for a conventional drill stem test.         36

      21          Schematic illustration of various drill stem test conditions.      37
      22          Portion of a Laterlog-gamma ray-neutron log from a deep
                 well in northern Illinois.                                      41
      23         Portion of a sonic log from a deep well  in northern
                 Illinois.                                                      42
      24         Portion of a temperature log from a deep well in  northern
                  Illinois.                                                      43
      25a         Normal sequence of events as recorded on the chart in
                  a successful drill stem test.                                    46
      25b         Sequence of events as recorded in a drill stem test when
                  no fluids were produced.                                      46
       2^         Example of a plot of data from a drift stem test with dual
                  ciosed-in periods.                                             47
       27         Plot of extrapolated pressure from drill stem test data
                  from an injection well in Ohio.                                49
       28          Plot of pressure buildup data from an inject!vity test of
                  the Mt. Simon Formation in Ohio.                             50
       29          Plot of recovery data and matching-type curves for an
                   injection test of a well at Mulberry, Florida.                   52
       30          Hydrogeology of the lower Floridan aquifer in northwest
                   Florida.                                                      56
       31          Generalized north-south geologic section through southern
                   Alabama and northwestern Florida.                            58
        32         Theoretical potentiometric surface of lower limestone of
                    Floridan aquifer in late  1971.                                  59

                                                                (continued)
                                          viii

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CONTENTS - Continued

Figure No.                            Title
    33         Generalized flow net showing the potential  lines
                and stream lines in the vicinity of an injection well
                near an impermeable boundary.                                63

    34         Theoretical  potent!ometric surface of the lower lime-
                stone of the Floridan aquifer in 1971,  with flow lines
                showing the directions of aquifer water and wastewater
                movement.                                                   65
    35         Predicted and  probable actual extent of wastewater
                travel for a  well completed in a carbonate aquifer.             68

    36         Schematic diagram of pressure versus time during
                hydraulic fracturing.                                          70

    37         Schematic diagram of an industrial waste injection
                well completed in competent sandstone.                        73

    38         Pressure history of a well injecting into a  carbonate
                aquifer.                                                      74

    39         Semi logarithmic plot of two pressure fall-off tests
                measured for an injection  well of the Monsanto Com-
                pany, Pensacola, Florida.                                    75

    40         Monthly average injection index for two injection
                wells of the Monsanto Company, Pensacola, Florida.           76

    41         Pipe Inspection Log and photographs of casing pulled
                after log was run.                                             78
    42         Portion of a casing inspection log run  in a wastewater
                injection well  showing apparent corrosion.                     79

    43         Preinjection and postinjection caliper logs from a
                wastewater injection well at Belle Glade, Florida,
                showing solution of the limestone aquifer in  the 1500-
                to 1600-ft interval by acidic  wastewater.                       80

    44         Borehole televiewer log of a section of casing showing
                casing perforations, packing seat and  casing collar.             81

    45         Borehole televiewer log showing vertical fractures in
                the borehole wall of a  well in Oklahoma.                      82
    46         Schematic diagram of a cement bond logging tool in
                a borehole.                              .                     83
                                                          (continued)

                                       ix

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ILLUSTRATIONS - Continued

Figure No.                           Title                                  page

    47         Portions of a cement bond log from an acid wastewater
                injection well.                                                84

    48         Geologic column and construction of a wastewater
                injection well at Mulberry, Florida, where two aquifers
                above the injection zone are monitored through the
                injection well.                                                39
                                LIST OF TABLES
Table No.                             Title

     1           Typical description of a core from the top of the Mt.
                Simon Formation in Illinois.                                   U

     2           Analysis of water from  the Mt. Simon Formation in
                the vicinity of Bloomington, Illinois.                          16

     3           Table of equivalency of permeability values.                    26

     4           Laboratory core analysis data from the Mt. Simon
                Formation in Illinois.                                          Oj,
                                                                             O4
     5           Welllogging methods and their applications.                    39

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                              SECTION I
                            CONCLUSIONS
   The subsurface environment is a complex one characterized by the
rocks and their structure, lithology, contained fluids and other resources,
and mechanical properties.  The static and dynamic states of the rocks
and fluids are also characteristic of a region and a specific location.

   An estimate of the characteristics of the subsurface environment can
be made prior to drilling of a well based on projections of data from out-
crops, previously drilled wells,  and possibly surface geophysical studies.
A much more accurate knowledge of the local subsurface environment is
obtained when a well is drilled and tested.  Data obtained from a well are
based on rock and fluid samples, geophysical logs, and pumping or injec-
tion tests.

   When the characteristics of the subsurface environment have been
estimated or determined, the response to wastewater injection can be
predicted.  Such predictions are  essential to monitoring because they
provide a baseline of expected performance, including rate of pressure
buildup and rate and direction of  travel of injected wastewater.

   The principal means of injection-well monitoring is of the injection
well itself.  This provides more  protection than is  commonly realized,
because the well is,  in most cases, the most likely source of escape of
injected wastewater.  Periodic inspection and testing of injection well
facilities complements continuous monitoring of well performance and
should prove helpful in detecting  deterioration of these facilities prior
to  failure.

   Monitoring wells  can be used for several purposes; they may be con-
structed in the injection aquifer,  in or just above the confining beds, or
in freshwater aquifers.  Local geology and hydrology, the waste being
injected, and economics are factors in determining if monitor wells are
needed, and, if so, how many and where.

   Other types, of monitoring include surface geophysics, sampling of
springs, streams, and lakes, and monitoring to record any seismic events
which might be related to operation of the injection well.

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                              SECTION II
                          RECOMMENDATIONS
   Monitoring of subsurface wastewaters injection should be thought of
as the full spectrum of consideration given to determining the effects of
a wastewater injection system from planning of the system through well
construction,  testing,  operation, and abandonment.

   Policy guidelines of the Environmental Protection Agency  and of The
Ohio River Valley Water Sanitation Commission (ORSANCO) should be
used as a basis for injection well monitoring.  These sources also provide
suggestions for a suitable data base for monitoring and ORSANCO outlines
a series of administrative procedures that should be followed.

   This publication provides a discussion of the tools and methods for
obtaining the needed data base and of the use of the resulting  subsurface
data for prediction and interpretation of well behavior during operation
It also discusses the surveillance of operating wells in some  detail  The
maximum use should be made of the methods  and tools that are available
consistent with the practicalities of available  resources.  Because of the
obvious complexity of many of the tools and methods,  regulatory agencies
should not hesitate to request the assistance of other public agencies and
of prxvate consultants in monitoring injection  systems

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                              SECTION III
                            INTRODUCTION
   As of mid-1973,  at least 278 industrial wastewater injection wells had
been constructed and 61 percent of them were operating (Warner and
Orcutt, 1973).  This is a relatively small number of waste disposal units,
but the number has continued to increase at a rate of about 30 wells an-
nually and could increase even more rapidly in response to the objective
of eliminating discharge to surface waters and in response to demands of
new technologies such as geothermal energy production,  desalination,
and radioactive waste disposal.  Regardless of the number of industrial
wastewater injection wells, they have been an object of unusual attention
by regulatory agencies  and by environmentalists.

   This attention is  reflected by inclusion of specific references to dis-
posal wells in Public Law 92-500, the Federal Water Pollution Control
Act Amendments of  1972.  A provision of that Act is the  requirement that
the Administrator of the Environmental Protection Agency shall, in coop-
eration with the States or other Federal agencies, establish a system for
the surveillance of the quality of surface waters and ground waters.  The
enactment of Public Law 93-253, the Safe Drinking  Water Act, further re-
quires the Administrator to propose and promulgate for State underground
injection programs minimum monitoring requirements to assist in prevent-
ing underground injection which endangers drinking  water sources.

   This publication provides technical information concerning  data needed
for monitoring and the methods and tools available for monitoring  of
wastewater injection wells and examples of their application.  However,
the material presented  cannot be expected to satisfy the monitoring re-
quirements of all aspects of underground fluid injection that will likely be
included in the rules and regulations that are promulgated in response to
P. L. 93-523. {The definition of the  term underground injection is  suffi-
ciently broad in P. L. 93-253 to include subsurface emplacement of fluids
by many means, such as ponds, pools, lagoons, and pits.} This  publica-
tion relates specifically to the subsurface eiriplaceinent of fjgid^B  tiiraugjb^
cased disposal wells.               ~  '

   To some, monitoring of ground water is often thought of as the observa-
tion of groundwater quality by sampling of wells and springs.   In this pub-
lication,  monitoring is meant to include the full spectrum of consideration

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INTRODUCTION
given to determining the effects of wastewater injection systems, from
planning of the system through well construction, testing, operation
and finally abandonment.  The policy of the Environmental Protection
Agency is consistent with this approach (see Appendix; also,  Hall and
Ballantine,  1973).  ORSANCO (Ohio River Valley Water Sanitation Corn-
 '1            * alS° haS established a basis
   *                                          injection well monitoring.
Both the EPA policy statement and the ORSANCO publication provide sue-
gestions for a suitable data base for monitoring.  ORSANCO  also sugeests
a series of administrative procedures, which, if followed, assure the
early involvement of regulatory agencies in monitoring and provide for
their  continued surveillance of injection systems throughout construction,
use, and abandonment.

   This publication is intended to complement existing ones,  such as those
mentioned above, by providing a more extensive discussion of the data
that characterize the subsurface environment, of how these data are ob
tamed,  and of how they are used to predict and interpret injection well
response.  The surveillance of operating injection wells is also treated
in more detail here than in earlier publications.

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                              SECTION IV
                    THE SUBSURFACE ENVIRONMENT
   In devising a monitoring program for a wastewater injection system,
the first consideration is definition of the regional and local subsurface
environment.  Factors in such an appraisal are stratigraphic and struc-
tural geology, lithology, fluid properties, mechanical properties of injec-
tion and confining units, hydrodynamics, and subsurface resources.  Other
publications (Warner,  1965 and 1968) have reviewed, in general, the rela-
tion of the subsurface environment to wastewater injection.  The purpose
of the following discussion is to provide more specific detail and examples
of the methodology for applying these concepts to monitoring.  It will be
attempted, insofar as possible, to avoid repetition of material that has
been previously presented.


STRATIGRAPHIC GEOLOGY
   Regional stratigraphy is determined by use of outcrop and borehole
data which have been interpreted and are generally presented in the form
of columnar sections,  isopach maps, facies maps, and cross sections.

   The basic data unit used in  studies of stratigraphic geology is the col-
umnar section, which is a graphic  representation of the sequence, thick-
ness,  lithology, and relationship of the rock units at a location.  A gen-
eralized columnar section may be prepared, which shows these parameters
for a region.  Figure 1 is  a generalized columnar section for northeastern
Illinois.  Columnar sections are prepared by using cores,  cuttings, and
geophysical logs from boreholes and, where outcrops are present, from
them.   Some possible injection horizons in Figure 1 are the St. Peter,
Ironton, Galesville, and Mt. Simon Formations.  Of these, the Mt. Simon
is the  deepest, and can be seen to be overlain by the Eau Claire Forma-
tion, which may contain confining shale beds.  On the other hand, the St.
Peter  Formation is shallower  and is  overlain by limestones and dolomites
which  are less dependable as aquitards; and, therefore, the St. Peter has
a lesser potential for wastewater injection.

   Isopachous maps indicate, by contour lines, the varying thickness of
a stratigraphic unit.  Figure 2 is an isopachous map of the Mt. Simon
Formation in Illinois,  showing that this sandstone unit varies in thickness

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THE SUBSURFACE ENVIRONMENT
SYS-
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LITHOLOGY
Shalt, rtd, htmatitic, oolitic
Shalt, dolomilic, grttnitti gray
Oolomitt and linw«iont, coortt groined;
\iholt, grttn
Sholt, dolomilic. brownish gray
Oolomitt, butt, medium grointd
Dolomitt.bjH. rtd Iptckltd
Oolomitt ond limtitent, buff
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Oolomitt ond limtttont, oronge sptckltd
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Sondttont ond dolomit*
Sondstont, lint; robot* ot bott
Dolomift, tondy
Sondttont, dolomitie
Oolomitt, nightly sondy; oolitic chtrt
Oolemitt. »ondy, oolitic ehtft
Oolomitt, slightly undy ot lop and
bost, light groy to light brown ;
gtodic quortz
Sond»ton«. dolomilt and sholt,
gtauconitic
Sondttont, mtdium grointd, dolomitie
in port
SOttlont, iholt, doiomilt, tondslon«,
glouconitt
Sanditant, lint lo eoortt gramtd
Figure 1.  Generalized columnar section of Cambrian and Ordovician strata in north-
          eastern Illinois (Buschbach,  19647 p. 16).

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                                                         STRATIGRAPHIC GEOLOGY
                               7      8	   9	10      It   R 12 E
46
                                                                     LAKE

                                                                   MICHIGAN
  2000'
      •  Well penetrating  complete
           thickness of Mt. Simon

      O  Well reaching arkosic zone
           but not base of Mt. Simon

         Isopach, interval 100 feet
               Miles
        0 	5     10    15
     Figure 2.  Isopach map of Mt. Simon Formation in northeastern Illinois
                (Buschbach, 1964).

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THE SUBSURFACE ENVIRONMENT
 from 0 to over 2, 000 feet within that State.  Other factors being equal,
 locations where the Mt. Simon Formation is thickest have greatest poten-
 tial for wastewater injection.

    The facies of a  stratigraphic unit are its laterally varying aspects,
 such as lithology,  fossil content, and so forth.  For example, the Eau
 Claire Formation, which overlies the Mt. Simon Formation,  consists
 of a mixture of siltstone, shale, dolomite, and sandstone in northeastern
 Illinois (Figure 1), but passes by facies  change eastward into sandstone
 in central Ohio and to dolomite in eastern Ohio (Figure 3).

    Some types of facies maps are ratio maps, percentage maps, and iso-
 lith maps.  These  facies maps  are different ways of showing the relative
 amounts of the various lithologies in a rock unit or units.  The ratio and
 percentage maps show contours of the  ratios or percentages of the aggre-
 gate thicknesses of lithologic classes.

    Figure 4 is a  lithologic ratio map, showing the relative ratios of sand-
 stone,  shale, and dolomite in post-Mt. Simon pre-Knox rocks in Ohio
 This figure generally shows that this group  of rocks changes from a sandy
 facies in western Ohio to a dolomite facies in eastern Ohio.  The rocks
 depicted in Figure 4 are equivalent to the Eau Claire Formation in Fig-
 ure 1.  So, in eastern Ohio, the Eau Claire Formation is almost entirely
 dolomite, rather than the mixed lithology shown in Figure 1.  Without
 further information, Figures 3 and 4 indicate that the Eau Claire Forma-
 tion becomes less  promising as a confining  unit for the Mt. Simon For-
 mation as it is traced eastward from Illinois into Ohio.
 WEST
EAST
                                        ROME FM  (dolomite)
                                    Rome sandstone facies
 Figure 3.  Schematic east-west section of the Eau Claire and equivalent Rome strata
          IJanssens/ Ir/o, p.  10).

                                   8

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                                                STRATIGRAPHIC GEOLOGY
                                              WW  W         -         "•
                                                      sand-shale ratio

 Figure 4.  Lithologic ratio map of post-Mt. Simon pre-Knox rocks (Janssens, 1973, p. 19).


   __.     -• •       _ _ j 	^ _ A.	— — MM. M«V£ M^«% **.•€ ^D-» 1 A**, rv^v j ** «*^v^*lf^ a i^i-^r+-^*^*H -v^ rt
   Figure 5 is an east-west cross section of Paleozoic rocks extending
from east-central Illinois to northwestern Pennsylvania.  This cross
section shows the facies changes in the Eau Claire that are described
above and shown in earlier figures.  The cross section also shows that
the Mr. Simon Formation is about 1, 500 feet thick in east-central Illinois,
but thins to about 100 feet across northern Ohio and into northwestern
Pennsylvania. Thus, much of the same information conveyed in the pre-
vious figures is summarized in a readily understandable form in such a
cross section.

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                                                                                                                          CO


                                                                                                                          CD
                                                                                                                          n
                                                                                                                          m
                                                                                                                          m
                                                                                                                          z
                                                                                                                          o
Figure 5.  Easf-west cross section of Paleozoic rocks in the northern Ohio River Valley — modified after cross sections in
          American Association of Petroleum Geologists cross section Publication 4,  1966 (Ohio River Valley Water
          Sanitation Commission, 1973, p. 51).

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                                                                  LITHOLOGY
   Local stratigraphy is first projected from regional data before drilling
of a well, then determined in detail for the well when it is drilled.  As
previously mentioned, the means of displaying the stratigraphy of a well
is the columnar section.


STRUCTURAL GEOLOGY

   Structural geology means the folding,  faulting, and fracturing of rocks
and the geographic distribution of these features.  One means of showing
regional  structural geologic features is a map which includes  areas or
lines of major features.  Figure 6 is such a map for the Ohio  River Basin.
Another type of map is the structural contour map.  Figure 7  is a struc-
tural contour map on the top of the  Mt. Simon Formation in Illinois.  Such
a map allows an estimate of the approximate depth to the mapped unit and
shows the location of known faults and folds that may influence decisions
concerning the location and monitoring of an injection well.
LITHOLOGY
   Lithology refers to the composition and texture of a rock.  The gener-
alized columnar section in Figure 1 contains brief, highly generalized
lithologic descriptions of rock units in northeastern Illinois.  The descrip-
tions prepared for individual wells are very detailed.  An example of a
description of a core from the top of the Mt.  Simon Formation in one well
is shown in Table 1.

     Table 1.  Typical description of a core  from the top of the Mt. Simon
             Formation in Illinois.
        Depth in Well
       3019.4-3020.5
       3020.5-3021.8
       3021.8-3023.8
           Lithologic Description
Sandstone; grayish-white; medium to very coarse
grained; grains are  broken, pitted, and chipped;
very cohesive and hard; very tight; semi-quartzitic.

Sandstone; as above; very poor sorting; medium to
very coarse, rounded grains, with abundant fine-
grained matrix; glassy; slightly pyritic; cohesive
and hard; not as tight as above zone; limited mud
invasion.

Sandstone; good sorting; very fine to fine,  sub-
angular grains; slightly pyritic; cohesive and
firm; limited mud invasion; very few shale
laminations.
                                    11

-------
     .;-^>-"^l
     ..'vT. ^«.« y
1^—^l_   V'. '/>,•//
                                                                    ^	  AKIS Of MAJOft SVNCIIMAt lOtO



                                                                  ^*^»* Vi^l  MflAMOIPMK AMD IQMfOHl CITSTAUMC •<

                                                                  IL >> ^ V^j  raUHAIKT Of mCAMHIAM A«l


                                                                   I I I I I M  AK«I W COMHII lAIHTHW M COKrUI

                                                                   I I I I I II  (AIMIKM AND tOitma
                                                                                                                            I
                                                                                                                            m
                                                                                                                            t/>
                                                                                                                            09
                                                                                                                            to

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                                                                                                                            >
                                                                                                                            o
                                                                                                                            m
                                                                                                                            m
                                                                                                                            Z

                                                                                                                            30
                                                                                                                            O

                                                                                                                            1
                                                                                                                            Z
Figure 6.  Map of the Ohio River twin anc! vicinity showing some major geologic features.  Data modified

           from published maps (Ohio River Valley Sanitation Commission,  1973, p. 24).

-------
                                                         LITHOLOGY
                                                               100
    --3000-
                     TENN.
                   Contour, intervol  1000  ft
                                                   Kilometers
    ^^ rr^rft^r     Fault, downthrown  side  indicated
Figure 7. Structure on top of Mt. Simon Formation (Bond,  1972, p. 36).
                              13

-------
 THE SUBSURFACE ENVIRONMENT
   Such detailed descriptions are prepared from cores, cuttings, and
geophysical logs, and are necessary for determining the rock-unit char-
acteristics in a test well.  From such descriptions, and other data,  in-
jection intervals, confining beds and casing points are selected and other
engineering decisions are made.

FLUIDS

Chemistry

   Judgment as to whether wastewater may or may not be permitted to be
injected into a rock unit depends, in part, on the chemistry of the aquifer
water.  The chemistry  of aquifer water is also important because of the
possibility of reactivity with injected wastewater.

   Policy concerning the minimum salinity of water in aquifers approved
for wastewater injection varies by State.  In the Ohio  Valley region,
Illinois agencies have determined that groundwater containing leas than
10,000 mg/liter total dissolved solids should be oroter.fp.fi-  jn New York
waste injection is prohibited in aquifers with a dissolved solids content
of 2,000 mg/liter or less.  In  Florida, the limiting value is 1,500 mg/liter.

   The problem of  potential reactivity between wastewater and aquifer min-
erals and water is  summarized by Warner (1968).  Several recent papers
concerning this topic are contained in the Proceedings of the Symposium
on Underground Waste Management and Environmental Implications  (Cook,
1972).

   In order to evaluate  the details of the  chemistry of aquifer water  it is
necessary to obtain samples after a well is drilled; samples from pre-
viously drilled wells may provide a good indication of what will be found
Geophysical logs are also useful for estimating the dissolved solids  con-
tent of aquifer water in intervals that are not sampled,  as will be discussed
later.

   In Illinois, the Mt. Simon Formation has been found to contain water
ranging in dissolved solids content from  less than 1, 000 mg/liter in the
northern part of the State to over 300, 000 mg/liter in the southern part.
Such information can be displayed in the  form of an i so con map (Figure 8).
Most of the dissolved solids are sodium chloride,  but significant amounts
ol calcium, magnesium, and sulfate are  also present (Table 2).

Viscosity

   Viscosity is the ability of a fluid to resist flow, and is an important
property in determining the rate of flow of a fluid through porous media.
                                  14

-------
                                                                FLUIDS
       Figure 8.  Isocon map, showing the dissolved solids content in
                parts per million of water in the upper 100 feet of
                the Mt. Simon Formation in Illinois.

The common unit of viscosity is the poise, or the centipoise, which is one
one-hundredth of a poise. Figure 9 shows the variation in viscosity of
water with temperature and salinity.  Both temperature and dissolved
solids content can have a significant effect.  In most cases,  the effects
will be offsetting in subsurface waters, since temperature and dissolved
solids content both tend to increase with increasing depth.  The viscosity
of some waste waters may be unusually high as a result of the presence
of dissolved organic chemicals.  Pressure in the range of interest has
an insignificant effect on viscosity.
                                   15

-------
THE SUBSURFACE ENVIRONMENT
      Table 2.  Analysis of water from the Mt. Simon Formation in the
               vicinity of Bloomington,  Illinois.
Analysis
Specific gravity
PH
Hydrogen sulfide
Carbonate alkalinity
Bicarbonate alkalinity
Chlorides
Total hardness
Calcium
Magnesium
Sul fates
Manganese
Total iron
Total dissolved solids (calculated)
Result
1.050
6.6
0.0
0.0
68
39,250
17,900
5,200
1,190
1,700
1.3
27.0
65,460


mg/liter
mg/liter
mg/liter
mg/liter
mg/liter
mg/liter
mg/liter
mg/liter
mg/liter
mg/liter
mg/liter
 Density

   The density of a fluid is its mass per unit volume.  The density of a
 liquid increases with increased pressure and decreases with increased
 temperature. However, the density of water changes  very little within
 the range of pressures and temperatures of interest.  For example, the
 density of water decreases only 0.04 gm/cm3 between 60°F and 210°F
 (Figure 10), and increases only about 0, 04 gm/cm3 from 0 to  14, 000 psi
 (Figure 11).  A more important influence on the density of water is the
 total dissolved solids content. Figure 12 shows the effect of various
 amounts of sodium chloride on specific gravity (or density). *  Since nat-
 ural brines may differ significantly from  sodium chloride  solutions, it
 may be desired to develop empirical relationships between density and
 dissolved solids as was done by Bond (1972) for the Illinois basin (Figure 13).
 *Specific gravity is the ratio of the mass of a body to that of an equal
  volume of pure water,  so for practical purposes, the numerical values
  of density and specific gravity are equal.  Specific gravity, however, is
  is dimensionless.
                                    16

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                                                             FLUIDS
                                     180,000 PPM

                                          240,000 PPM
      68   100      150      200      250      300
                RESERVOIR TEMPERATURE (*F)
350
Figure 9.  Water viscosity as a function of temperature and salinity
         (ppm NaCI) (Pirson, 1963, p. 40).
                              17

-------
THE SUBSURFACE ENVIRONMENT
    8
    UJ
    UJ
    UJ
    cc
    y
    t
    u
I.U IV
1.000
0.990
0.980
0.970
0.960
0.950
0.940
0.930
0.920
0.910
— ••








i™»








-=









^









•^X










X









x
^









X










\









\
s









N.
>,









s










\










k










\

40 80 120 160 200 240 280 320
TEMPERATURE, °F
               Figure 10.  Specific gravity of distilled water as a function
                           of temperature (Pirson,  1963,  p.  39).

                                     PROPERTIES OF LIQUID WATER
                Figure 11.  Specific volume of water as a function of temper-
                           ature and pressure (Eisenberg and Kauzmann,  1969.
                           p. 186).
                                         18

-------
                                                                  FLUIDS
     a
     u.
     (ft
                      50,000    100,000    150,000
                               TOTAL SOLIDS (PPM)
200,000   250,000
          Figure 12.  Specific gravity of formation waters (D^) versus total
                    solids in ppm (data for NaCl solutions)  (Pirson, 1963,
                    p. 39).
Pressure
   A knowledge of fluid pressure in the unit proposed for wastewater
injection is important.  Fluid pressure can be measured directly in the
borehole at the depth of the injection horizon, usually by performing a
drill-stem test, which will be described later.  Fluid pressure at the
injection horizon can also be measured indirectly by determining the
static water level in the borehole, then computing the pressure of the
fluid column at the depth of interest.

   Figure 14 shows how fluid pressure increases with depth in a well
bore filled with freshwater with a specific gravity of 1.0.  When the aver-
age specific gravity of the water or wastewater is other than 1. 0 the rate
of pressure increase varies accordingly.  For example,  if a well bore
is filled with formation water with a dissolved solids content of 65, 000
mg/liter and a specific gravity of 1. 05, then fluid pressure increases at
a rate of 0.455 psi/ft,  and would be 455 psi at the bottom of a 1, 000-ft-
deep water-filled well.  The fluid pressure must be added to the pump
pressure in injection calculations to determine the total pressure.
                                   19

-------
THE SUBSURFACE ENVIRONMENT
     280,000
     260,000 -
     240,000 -
     220,000 -
     200,000 -
     180,000 -
  0  160,000 -

  8
  Q
  >  140,000 -
     120,000 —
     100.000 -
      80,000 -
      60,000 -
      40,000 -
      20,000 -
             1-00   1.02     1.04    ,.08     ,.08    ,.10     ,.„

                                RELATIVE DENSITY, p
      Figure 13.  Relation between relative density and dissolved solids content of
                  brines in deep aquifers of the Illinois basin (Bond, 1972).
                                           20

-------
                                                                 FLUIDS

^
1
1


















Xj- 1 i
*/\
1
I 	
/r
i
,* —
i
A~
i
/T~
i
I
/!
1
i
>T-
^x 1

/T~
/

/ i
i
1
/| —
X i

/
Ft —
y

X

7

/

7

/

7

7

7

7

7

<"»•£/&

0.433

0433

0433

0 433

0.433

0.433

0.433

0.433

0.433

4.33 P*l"0
                                                 psi/ft
                 Figure 14. Hydraulic pressure gradient in a
                           column of water (Katz and Coats,
                           1968, p. 11).

   Although instances of truly anomalous formation pressure are likely
to be relatively rare at sites selected for wastewater injection, the
existence of unusually high or low pressures and the possible reasons
for their existence should be recognized.  Some causes of anomalous
pressure are:
         1.  Compaction of sediments

         2.  Tectonic forces
                                   21

-------
THE SUBSURFACE ENVIRONMENT


         3.  Osmotic effects

         4.  Massive extraction or injection of fluids.

   Abnormally high pressures can result from 1, 2, and 3 and from mas-
 sive injection.  Abnormally low pressures can result from osmotic effects
 and extraction of fluids.  Abnormally high pressures resulting from com-
 paction of sediments are common in deep  wells of the Gulf Coast (Dickinson,
 1953).  Berry (1973) concluded that abnormally high pressures in the Cal-
 ifornia Coast Ranges are a result of tectonic forces.  Hanshaw (1972) dis-
 cussed natural osmotic effects and their relation to subsurface wastewater
 injection.

 Compressibility

   The compressibility of an elastic medium is defined as;
where   j3 = compressibility of medium (pressure'1)
         V = volume
         p = pressure
 with dimensions
         F = force
        L,2 = area.
   The compressibility of water varies both with temperature and pres-
 sure  as is shown in Figure 15.  For problems in wastewater injection,
 ft will generally be within the range of 2. 8 to 3. 3 X  1Q-& psi-l  and
 3. 0  x  10-0 psi-l  is a reasonable value to assume in most case's.

 MECHANICAL PROPERTIES OF INJECTION AND
 AND CONFINING  UNITS
 Porosity

   Porosity is defined as:
         ^ = v~   (dimensionless)                                 ,,.
               t                                                    * '

 where   0   =  porosity, expressed as a decimal fraction
         Vv  =  volume of voids
         Vt  =  total volume of rock sample.

    Porosity is also commonly expressed as a percentage.  Porosity may
 be total porosity or effective porosity.  Total porosity is a measur* £
 all void space.  In comparison with total porosity, effective porosity is
                                  22

-------
                                               MECHANICAL PROPERTIES OF
                                       INJECTION AND CONFINING UNITS
                 PRESSURE-PSI A
                      1000
                   100
   150      200
TEMPERATURE-°F
                                               250
300
     Figure 15.  Compressibility of water (Katz and Coats,  1968, p. 93).

based on the total volume of interconnected voids.  Effective porosity
better defines the hydraulic properties of a rock unit, since only inter-
connected porosity is available to fluids flowing through the rock.  In the
remainder of the report,  reference to porosity implies effective porosity
unless otherwise stated.

   Porosity may also be classified as primary or secondary.   Primary
porosity includes original intergranular or intercrystalline pores and the
porosity associated with fossils, bedding  planes, and so forth.  Secon-
dary porosity results from fractures, solution channels, and from re-
crystallization and dolomitization.  Intergranular porosity occurs prin-
cipally in unconsolidated sands and in sandstones, and can be measured
reasonably well in the laboratory using core samples taken from wells.
Porosity contributed by fractures and solution channels is difficult to
measure in the laboratory.  Various  borehole geophysical methods that
will be discussed later can be used to determine the porosity of strata in
place.   Porosity values in reservoir  formations range from a maximum
of about 0.40 in unconsolidated sands to as little as  0. 02 in dense lime-
stones. Porosity in the Mt.  Simon Formation of Illinois ranges from
about 0. 20 to 0. 02, as shown in Figure 16.
                                  23

-------
THE SUBSURFACE ENVIRONMENT
       POROSITY IN PERCENT
           Figure 14.
                                dtorIb(jH  •
                                24

-------
                                              MECHANICAL PROPERTIES OF
                                      INJECTION AND CONFINING UNITS
Permeability
   Permeability is the capacity of a rock to transmit fluid.  Permeability
is quantified by the coefficient of permeability or hydraulic conductivity.
When both the properties of the_fluid and the porous medium are considered,
the coefficient of permeability K is defined by Darcy's law as:
                       ,L2)                                        (3)
              Apg dh   (L >
where   Q  =  flow rate through porous medium
         A  =  cross- sectional area through which flow occurs    r
         ji  =  fluid viscosity
         p  =  fluid density
         L  =  length of porous medium through which flow occurs
         h  =  fluid head loss along L
         g  =  acceleration of gravity.

   The unit of permeability used in oil field work is the darcy. Substitu-
tion of p = pgh into Equation 3 results in Equation 4:



         K  =  f f   ^

From Equation 4, the darcy has been defined as

                   1 cm3 /sec X  1 centipoise  X  1  cm
         1 darcy = -
                         1 cm  x  1 atmosphere

   A still simpler form of Darcy's law is used in groundwater studies
where the density and viscosity of water
         K =         (L/T)   .                                      (5)
             A dh

   The constant K is referred to as hydraulic conductivity and is usually
 expressed with the dimenstions cm/sec (L/T) or in U.S. Geological Survey
 units which are gallons/day x ft2 (meinzers).  A table for conversion of
 permeability units is given below (Table 3).

   Permeability values for the formations used for wastewater injection
 range generally from several darcys to less than a millidarcy (one milli-
 darcy = 10~3 darcy). Average permeability values for the Mt.  Simon
 Formation in Illinois range from more than 100 millidarcys in the north
 to less than 1 millidarcy in the south.  The permeability of shale beds
                                 25

-------
THE SUBSURFACE ENVIRONMENT
                Table 3.  Table of equivalency of permeability values
                         in various units (Davis and Deweist, 1966,
                         p. 165).
              1 darcy
              10-10 Cm2
              0.1 cm/day

              1.0 cirv/sec
              1 darcy
              1 me Inzer
                    = 9.87 x 10-9 cm-2 = 1.062 x 10"!
                    = 1.012x 10-12 darcys
                    = 1.15x 10-6 cm/sec « 1.18x 10"1] cm2
                      for water at 20° C
                    « 1.02 x 10"5 cm2 for water at 20°C
                    t* 18.2 meinzer units for water at 60°F
                    = 0.134 ft/day = 4.72 x 10'5 cm/sec «
                      5.5 x 10"2 darcys for water at 60°F
in the Eau Claire Formation, overlying the Mt.  Simon Formation, is
consistently less  than 0.001  millidarcy.
   A useful constant in hydrogeologic work is the coefficient of transmis-
™    rT^i88^50 WhiCh " the Permeabil"y or hydraulic conductivity
multiplied by the  thickness of the aquifer.  When the unit of permeability
is the darcy, transmissivity is in darcy-feet/centipoise.

Compressibility
   The compressibility of an aquifer includes the compressibility of the
    £1athe                       •  *•
where
C  =

C  =
0
                       (F/L2)
                              -1
                                                                     (6)
compressibility of aquifer (pressure"1)
porosity
compressibility of water
compressibility of aquifer skeleton.
                       °
   "
               v   ,
              skeletons  varies greatly,
                                                    discussed.  The com-
                                                                        -8
   The coefficient used in analysis of reservoir response to injection or
pumpxng ,s the storage coefficient (storatlvity), which is defined b"°

-------
                                                  MECHANICAL PROPERTIES OF
                                          INJECTION AND CONFINING  UNITS
         S = 0yb (0 + •?)  (dimensionless)                          (7)

where 0 , /3,  and a are as previously defined, and
         S = storage coefficient
         y = pg = specific weight of water per unit area
         b = aquifer thickness.

   The storage coefficient is the  volume of water an aquifer releases or
takes into storage per unit surface area per unit change in hydraulic head.
The storage coefficient may be estimated from the equation above, or may
be determined from aquifer tests that will be described later.  Values of
S are reported to range from 5 X lO'5 to  5 X 10~3 for confined aquifers.
As  an estimate of the value of S  for the Mt.  Simon Formation in northern
Illinois assume that 0  = 11 percent, b = 1,700 ft,  7 = 0.45 psi/ft, ft =
3.0  X 10-6  psi-1, and* a = 6.7  X  10'^.  Then, from the equation above,
S « 5.4  X 10-3.  This is a high value, but the aquifer is very thick.  If
the compression of the water alone were considered, then S  would be
2.5  X 10-4.  The Illinois State Water Survey  (1973) estimated an average
storage coefficient of 1 X 10'4 for the Mt. Simon Formation in northern
Illinois,  which is probably too low if the entire thickness of the formation
is considered.


Temperature
   The temperature of the aquifer and its contained fluids is important
because  of the effect that temperature has on fluid  properties.  The temp-
erature of shallow groundwater is generally about  2° to 3° greater than the
mean annual air temperature.  In Illinois, this is from about 60°F in the
south to  50°F in the north.  Below 30 to 60 feet, the temperature increases
approximately 1° to 2°F per  100  feet of depth.  Figure 17 is a geothermal
gradient map of Illinois and Indiana.  At a depth of 3, 000 feet, in northern
Illinois,  the calculated temperature would be about 86°F.  The measured
temperature at 3,000 feet near Pontiac, Illinois, was 90°F.  Geothermal
gradient maps for the United States have been prepared by the American
Association of Petroleum Geologists (AAPG),  Tulsa, Oklahoma, and can
be obtained from that organization.  Figure 17 is a modification of one of
the AAPG maps.
*Testing of the Mt. Simon Formation, in a gas storage field in northern
 Illinois,  yielded a value of compressibility of the formation and its con-
 tained water of about 7 X lO'6.  Since the water only occupies 11 percent
 of the rock, the rock skeleton compressibility at that location is 6. 7 X
 10-6.
                                 27

-------
THE SUBSURFACE ENVIRONMENT
                                                               FEET
                                                 TEMPERATURE DATA POINT
                                                  TEMPERATURE GRADIENT
                                                     t'Am FEET
                                                        I.2.J.6
                                                        1.6-2.0
                                                        >2.0
     Figure
17.  Reproduction of portfolio map No.  10, American Association
    of Petroleum Geologists Geothermal Survey of North America
    (Gould, 1974).
 State of Stress
   In order to predict the pressure at which hydraulic fracturing or fault
movement would be expected to occur, it is necessary to estimate the
state of stress at the depth of the injection horizon.  On the other hand,
determination of the actual fracture pressure allows computation of the
state of stress (Kehle, 1964).
    The general equation for total normal stress
 medium is:
         St  =  Po+Cri
                                     across a plane in a porous
                                                           (8)
                                    28

-------
                                                     HYDRODYNAMICS
 where   S^  = total stress
         p0  = fluid pressure
         Cfi  - effective or intergranular normal stress.

    Effective stress, as defined by Equation 8, is the stress available to
 resist hydraulic fracturing or the stress across a fault plane that acts to
 prevent movement on that fault.  The equation shows that, if total stress
 remains constant, an increase in fluid pressure reduces the effective
 stress  and a decrease in fluid pressure increases effective stress.  When
 the effective stress is reduced to zero by fluid injection,  hydraulic fractur-
 ing occurs.  Fault movement will occur before normal stresses across the
 fault plane are reduced to zero, since there must be some shear stress act-
 ing on the fault blocks to cause them to move.

    In a sedimentary rock sequence, the total normal vertical stress in-
 creases with depth of burial under increasing thicknesses of rock and
 fluid.   It is commonly assumed,  and the validity of the assumption can
 easily be verified, that the normal vertical stress increases at an average
 of about 1 psi/ft  of depth.  The lateral stresses may be greater or less
 than the vertical stress, depending on geologic conditions.  In areas where
 crustal rocks are being actively compressed, lateral stresses may exceed
 vertical ones. In areas where crustal rocks are not in active compression,
 lateral stresses  should be less than the vertical stress. The basis of esti-
 mating lateral stress prior to  drilling of a well is hydraulic fracturing data
 from nearby wells and/or  knowledge of the tectonic state of the region in
 which the well is located.  The tectonic state of various regions is only
 now being determined.  For example, Kehle (1964) concluded, as a result
 of hydraulic fracturing data from four wells, that the stresses at the well
 locations in Oklahoma and Texas were representative of an area that was
 tectonically in a  relaxed state.  In contrast, Sbar and Sykes (1973) charac-
 terized much of the  eastern and north-central United States as being in a
 state of active tectonic compression.  Further discussion concerning the
 state of stress and hydraulic fracturing will be presented in the section
 on hydraulic fracturing.

HYDRODYNAMICS
   Hydrodynamics,  as the term has been adopted for use in subsurface
hydrology, refers to the state of potential for flow of subsurface fluids,
particularly in deep  sedimentary basins.   As examples of its application
 recent publications by Bond (1972) and Clifford (1973) discuss the flow
potential in deep  aquifers of Illinois,  Indiana,  and Ohio as determined
from pressure, water level, and water density measurements made in
deep wells.

   The potential for  flow in deep aquifers that are used for wastewater in-
jection is important, because it can be used to estimate natural groundwater


                                  29

-------
THE SUBSURFACE ENVIRONMENT
flow rates and directions.  Figure 18 is a map showing the potentiometric
surface of the Mt. Simon Formation Formation in Ohio and Indiana.   The
arrows indicate the directions of regional groundwater flow in the Mt.
Simon Formation as indicated by the potentiometric contours.  Bond
(1972 and 1973) discusses some of the difficulties in interpretation and
application of potentiometric data.

RESOURCES

   An objective in the monitoring  of subsurface wastewater injection is
to verify that fresh groundwater,  oil or gas,  coal,  or other subsurface
resources are not being jeopardized.  Therefore,  the occurrence and
distribution of all significant subsurface resources must be determined.
This determination is made by reference to published reports and by
consultation with  public officials,  companies, and individuals familiar
with subsurface resources of the area.  Also, the actual drilling of the
well will show the location and nature of resources present at depth at the
well site.

   In reviewing the occurrence of subsurface resources, the  locations,
construction, use, and ownership of all wells,  both shallow and deep
within the area of influence of the injection well should be determined.
The plugging  record for all abandoned deep wells should be obtained to
                                      Altitude ol potentiomeutc surface above s«a level
                                       (contour interval 200 feet, dashed where inferred)
                                      Inferred direction ol flow
         Figure 18. Potentiometric surface of the Mt. Simon Formation
                   In Ohio and vicinity (Clifford, 1973).
                                   30

-------
                                                          RESOURCES
verify the adequacy of such plugging. In States where oil has been pro-
duced for many years there are often areas where wells are known to
have been drilled, but for which no records are available,  and there are
also wells which are located but for which plugging records are not avail-
able or for which plugging is known to have been inadequate. Document-
ing the status of deep wells near the injection well may be the most impor-
tant step in monitoring of injection wells in areas that are or have been
active oil or gas provinces, because these wells provide the greatest
hazard for escape of wastewater or formation water from otherwise well-
confined aquifers.
                               31

-------
                              SECTION V
                   ACQUISITION OF SUBSURFACE DATA
 PRIOR TO DRILLING

   In order to estimate the performance of injection wells and to evaluate
the subsurface environment prior to construction,  the types of information
described in Section IV, The Subsurface Environment,  are estimated from
sources  such as the figures and tables from that section.  The information
in those  figures and tables has, of course, come from previously drilled
wells; and  if it has not been compiled on maps, cross sections,  and tables,
then this may be necessary before it can be used.  Basic information for
previously drilled wells is available in most States through State geological
surveys, oil and gas agencies and water resources agencies.  In addition,
private companies acquire and sell well logs,  and  other subsurface data.
In some  cases it may be necessary to go to individual oil companies or
consultants for subsurface data that are not publically available. Com-
panies and individuals are usually cooperative in releasing information
that is not  considered confidential.

DURING WELL CONSTRUCTION AND TESTING
Rock Samples
   Most  deep wells drilled today are drilled by rotary drilling rigs   Ro-
tary drilling rigs use two basic types of drilling bits, rock bits  and core
bits.  Rock bits grind the strata into small chips that are usually carried
from the hole by a viscous drilling mud, but sometimes by water or air
The chips are periodically collected, usually after each 5 or 10 feet of
new hole, washed, and examined with a  low-powered binocular micro-
scope.  The methods for collection, examination,  and description of such
samples  are presented in a reference edited by Haun and LeRoy (1958)
Figure 19 is an example of a sample log prepared  by examination of cut-
tugs.  Soft, unconsolidated clays will not yield chips, but will break down
into mud and unconsolidated or  soft sandstones into individual grains when
drilled.  Samples  are of only limited value in  such areas.

   Cores taken with rotary core bits and barrels give a much more accur-
ate picture of the subsurface formations than cuttings,  but core samples
are very expensive (>$50/ft) in deep wells and can usually only be afforded
in limited numbers.  In deep wells, core samples  are commonly about
                                  32

-------
                                      DURING WELL CONSTRUCTION
                                                      AND TESTING
            Pe fining
NO.
             I/lustration   >*«*
 GMrfit/d   «».  Oklmhomm *rsn
  12 3f
                 y _
         Rotmry too/±_
         Discovery  Welj^
                                               LEGEND
                  &W
                                                   LimMtonc
                                                     . w/eh«rt
                                            IMS  I  N» Sample

                                                |   Oil Main
                                        Figure 19. Sample log
                                                  (Moore, 1951).
                          33

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ACQUISITION OF SUBSURFACE DATA
four inches in diameter.  Cores are described just as are cuttings, but
since a continuous sample of the formation is available, a detailed foot
by foot description can be prepared (Table 1).  Whole-core samples can
be analyzed for porosity and permeability in the laboratory, or small
cores  can be taken from the large core and analyzed.  The latter proce-
dure is the most common.  Table 4 shows typical laboratory core data
from the Mt. Simon Formation in Illinois.

         Table 4,  Laboratory core analysis data from the Mt. Simon
                  Formation in Illinois.0

Sample
Number
408
409
410
411
412
413
414
415
416
417
418
419
420
421
422
423
424
425
426
427
428
429
430
431

Depth
(feet)
3154.5
3155.5
3156.6
3157.5
3158.5
3159.5
3160.5
3161.5
3162.5
3163.5
3164.5
3165.5
3166.5
3167.5
3168.5
3169.5
3170.5
3171.5
3172.5
3173.5
3174.5
3175.5
3176.5
3177.5
Permeability
(millidarcys)
Horizontal
6.9
<0.10
<0.10
0.17
0.26
<0.10
1.9
<0.10
2.3
0.43
12.
3.1
0.31
7.8
8.5
5.0
6.2
3.4
10.
1.4
11.
8.5
2.6
0.74
Vertical
0.11
0.17
<0.10
0.31
0.72
<0.10
0.12
<0.10
0.98
0.46
0.12
1.1
0.44
0.79
5.4
3.2
3.6
1.2
2.5
0.46
2.0
1.5
0.91
<0. 10
Note:

Porosity
(percent)
6.4
6.4
9.7
8.6
8.3
8.1
9.6
8.7
8.1
6.2
8.2
14.7
10.7
10.0
9.9
7.2
6.9
8.3
12.2
8.9
8.0
8.2
7.7
5.9

Mt. Simon Core No. 15 3148.0 - 3178.0
                                  34

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                                              DURING WELL CONSTRUCTION
                                                            AND DRILLING
Formation Fluids
   Samples of water from subsurface formations can be obtained from
 deep wells before they are completed, from cores, by formation test-
 ing devices, and by swabbing.

   When cores are taken, as previously described, the water in the cores
 can be carefully extracted and its chemistry analyzed.  Contamination is
 a serious problem,  since the core has been exposed to  infiltration by
 drilling  mud and mud filtrate.

   Drill-stem testing is a technique whereby a zone in an open borehole
 can be isolated by an expandable packer or packers and fluid from the
 formation allowed to flow through a valve into the drill  pipe.

   The basic drill-stem test tool assembly consists of:
         1.  A rubber packing element or packer which can be expanded
             against the hole to segregate the  annular sections above
            and below the element
         2.  A tester valve to (a) control flow  into the drill pipe,  that
            is,  to exclude mud during entry into the hole and to allow
            formation fluids to enter during the test, and an equalizing
            or bypass valve to (b) allow pressure equalization across
            the packer(s) after completion of  the flow test.

   Figure 20 illustrates the procedure for testing the bottom section of a
hole. While going in the hole, the packer is collapsed,  allowing the dis-
placed mud to rise as shown by the arrows. After the pipe  reaches  bottom
and the necessary surface preparations have been made, the packer is set
(compressed and expanded); this isolates the lower  zone from the  rest of
the open hole.  The  compressive load is furnished by a  slacking off of
the desired amount of drill-string weight,  which is transferred to  the
anchor pipe below the packer.

   The tester valve  is then opened and thus the isolated section is ex-
posed to  the low pressure inside the empty, or nearly empty, drill pipe.
Formation fluids can then enter the pipe, as shown  in the  second picture.
At the end of the test, the tester valve is closed, trapping any fluid above
it, and the bypass valve is opened to equalize the pressure across the
packer.  Finally, the setting weight is taken off and the packer is pulled
free.  The pipe is then pulled from the hole until the fluid-containing
section reaches  the  surface.  As each successive pipe section is removed,
its fluid  content may be examined.

   Although the above is a very common type of test,  there are many other
variations of procedure, as indicated in Figure 21.  The straddle packer
                                 35

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ACQUISITION OF SUBSURFACE DATA
 PERFORATED
 ANCHOR PIPE
             GONGN
                                                                 REVERSING
           Figure 20.  Fluid passage diagram for a conventional bottom
                     section, drill stem test (Gatlin,  1960).
                                     36

-------
                                           DURING WELL CONSTRUCtlON
                                                          AND DRILLING
                             GENERAL PROCEDURE
       (A) STRADDLE PACKER
         TEST
                      IB) CONE PACKER TEST
(C) WALL OVER CONE
  PACKER TEST
(D) TESTING THROUGH
  PERFORATIONS IN
  THE CASINO
          Figure 21. Schematic illustration of various drill stem test
                    conditions (Kirkpatrick, 1954).

test is necessary when isolation from formations both above and below the
test zone is necessary.   Such a situation commonly arises when it is de-
sired to test a zone previously passed by.  Straddle testing is less desir-
able than conventional testing,  from both a cost and an operational hazard
standpoint.   Two packers are more apt to become stuck than one, since
any material which sloughs or  caves  from the test zone may accumulate
between the packers.  Also,  two positive, pressure-tight packer-formation
seals are required for a successful test.  Consequently this procedure is
not preferred, and is applied only when necessary.  This should not be
construed to mean that these disadvantages prevent one from making such
tests but rather that the additional problems the tests entail should be
recognized.

   Formation testing devices are available which can be lowered into the
borehole on a wire line.  In this case, the sample is limited to the amount
that can be contained in the testing device (up to about 5 gallons).

   Swabbing  is a method of producing fluid that is similar to pumping a
well.  In swabbing, fluid is lifted from the borehole through drill pipe,
casing, or tubing by a swab that falls freely downward through the pipe
and its contained fluid, but which seats against the pipe walls on the up-
stroke, drawing a volume of  fluid  above it as it is raised.  Swabbing may
be used in conjunction with drill-stem testing to increase the volume of
                                   37

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ACQUISITION OF SUBSURFACE DATA
fluid obtained.  The advantage of swabbing is that it can be continued until
all drilling mud has been drawn from the pipe and the formation and the
chemistry of the water obtained reaches a steady state.  This procedure
helps to insure that a representative sample of formation water is obtained.

Borehole Geophysical  Logs

   After  a well has been drilled, a variety of borehole logging tools  are
available  that can be used to produce a record of the nature of the forma-
tions penetrated and their contained fluids.   In borehole logging,  a probe
is lowered into a well  at the end of a wire cable and selected geophysical
properties are  measured and recorded at the surface as  a function of depth.

   Current methods of well logging are too numerous to discuss in detail
here.  A broad classification of the more commonly used methods is
shown in Table 5, together with their main applications.  Because the
variety of available logging methods is so great, the suite used in logging
a well must be  carefully selected to provide  the desired information at
an acceptable cost.  Local practice in the particular geographic area is
a valuable guide, since it represents the  cumulative  experience obtained
from logging many wells.  Some of the objectives in logging injection
wells will generally be:  determination of lithology; bed thickness; amount,
location and type of porosity; and salinity of formation water.  In order
to achieve these objectives,  a commonly chosen  suite of  logs will include
a gamma  ray log, a focused resistivity log,  and one or more porosity
measuring logs selected from among the various radiation  and elastic
7a!e !°,gc^  STe °ther fre
-------
                                                     DURING WELL CONSTRUCTION
                                                                      AND DRILLING
     Table 5.  Well  logging methods and their applications (modified after Jennings
               and Timur,  1973).
          Method
        Property
        Application
 01
M
y 3
h- <
ui §=
      Spontaneous
      Potential (SP)


      Nonfocused
      Electric Log
      Focused
      Conductivity Log
      Focused
      Resistivity Logs
      Focused and
      Nonfocused
      Microresistivity Logs
      Transmission
      Reflection
Electrochemical and
electrokinetic potentials


Resistivity
Resistivity
Resistivity
Resistivity
Compressional and
shear wave velocities
Compressional and
wave attenuations
Amplitude of reflected
waves
Formation water resistivity
(Ry/); shales and nonshales;
bed thickness; shaliness

a. Water and gas/oil satura-
   tion
b. Porosity of water zones
c. Rw in zones of known
   porosity
d. True resistivity of for-
   mation (Rf)
e. Resistivity of invaded
   zone

a, b, c, d
Very good for estimating Rj.
in either freshwater or oil
base mud

a,b,c7d
Especially good for deter-
mining fy of thin beds

Depth of invasion

Resistivity of the flushed
zone (RXO) for calculating
porosity
Bed thickness
••^••••«•
Porosity; lithology; elastic
properties, bulk and pore
compressibilities

Location of fractures;
cement bond quality
Location of vugs,  fractures;
orientation of fractures and
bed boundaries; casing
inspection
                                                            (continued)
                                           39

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ACQUISITION OF SUBSURFACE DATA
    Table 5 — Continued
         Method
                               Property
                                 Application
O
§
a
2
Gamma Ray

Spectral
Gamma Ray

Gamma-Gamma
Neutron-Gamma
Neutron-Thermal
Neutron

Neutron»sEpithermal
Neutron

Pulsed Neutron
Capture

Spectral Neutron
Natural radioactivity


Natural radioactivity

Bulk density
Hydrogen content

Hydrogen content


Hydrogen content


Decay rate of thermal
neutrons


Induced gamma ray
spectra
Shales and nonshales; shall-
ness

Lithologic identification

Porosity, lithology
Porosity

Porosity; gas from liquid


Porosity; gas from liquid


Water and gas/oil satura-
tions; reevaluation of old
wells

Location of hydrocarbons;
lithology
IU
x
Caliper

Dipmeter


Deviation Log


Gravity Meter

Ultra-Long Spaced
Electric Log

Nuclear Magnetism
     Production or
     Injectivity

     Temperature Log
Borehole diameter

Azimuth and inclination
of bedding planes

Azimuth and inclination
of borehole
Density
Resistivity

Amount of free hydro-
gen; relaxation rate of
hydrogen

Temperature, flow rate,
fluid specific gravity,
pressure

Temperature
Calculation of cement vol-
ume;  location of mud cake
Dip and strike of beds


Borehole position


Formation density
Salt flank location


Effective porosity and per-
meability of sands; porosity
for carbonates

Downhole production or
injection


Formation temperature
                                       40

-------
                                          DURING WELL CONSTRUCTION
                                                          AND DRILLING
                                               100 ohm-m
Figure 22.  Portion of a Later log-gamma ray-neutron log from a
           deep well in northern Illinois.
                               41

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ACQUISITION OF SUBSURFACE DATA
           o
           m
INTERVAL TRANSIT TIME
     MICROSECONDS PER FOOT
        Figure 23. Portion of a sonic log from a deep well in northern Illinois.
                              42

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                                          DURING WELL CONSTRUCTION
                                                          AND DRILLING
          2800
          2900
          3000
          3100
Figure 24.  Portion of a temperature log from a deep well in northern
           Illinois.
                                43

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ACQUISITION OF SUBSURFACE DATA
the Laterlog (Figure 22), the resistivity of this interval is about 40 ohm-
meters.  From the Archie equation (Schlumberger, 1972) the formation
factor F is 45 and the resistivity of the formation water is 0. 625  ohm-
meters.  A sodium chloride water with a resistivity of 0. 625 ohm-meters
has a dissolved solids content of about 8, 000 ppm at 83. 5°F,  Actually,
the formation water salinity is probably about twice the calculated value
because the Laterlog yields incorrectly high resistivities when run in
low-salinity mud, as is  the case here. An induction log would yield more
accurate results  in  such a situation.  This example illustrates some of
the principal uses of borehole geophysical logs in conjunction with the
evaluation of geological  conditions in wastewater injection wells.  Fur-
ther uses will be covered in Section VII,  on well monitoring.  Keys  and
Brown (1973) give a more complete discussion of the application of bore-
hole geophysical logs to wastewater injection than is possible here.


Testing of Injection Units and Confining Beds
    Examination of the records of many of the wastewater injection wells
that have been constructed up to the present time shows that, with few
exceptions,  the maximum amount of usable geologic and engineering in-
formation has not been obtained during the testing  of wastewater injection
wells. This is regrettable, because  such tests provide the best basis for
analyzing  reservoir conditions prior  to injection,  for predicting the  long-
 term  behavior of the well and the reservoir, for detecting and understand-
 ing changes in well performance that may occur during operation, and for
 analyzing  the  history of a well from its records.

    The methods for testing of pumping or injection wells and the techniques
 for analysis of test data are discussed in numerous textbooks and in hun-
 dreds of other publications concerning groundwater and petroleum engineer-
 ing.   Because the number of published articles and the scope of their con-
 tent are so  extensive,  only a few selected references are mentioned and a
 few examples discussed here to establish the reasons for and methods of
 well testing.

    A  well can be tested by pumping from it or injecting into it.  Measure-
 ments of reservoir pressure or water level can be made  during pumping
 or injection or, alternatively, after pumping or injection has ceased and
 the reservoir is adjusting to its original condition. Furthermore,  reser-
 voir  pressure or water level can be measured in the principal well or in
 adjacent observation wells. Any one of these approaches will yield much
 of the same information.
                                   44

-------
                                             DURING WELL CONSTRUCTION
                                                            AND DRILLING
 Drill Stem Test ing
    In the case of the usual deep and rather expensive wastewater injection
 well, there will be no observation well and testing will be in the well itself.
 In the sequence of well construction and testing,  the first type of formation
 test that is likely to be made is the drill-stem test (DST).  As has pre-
 viously been mentioned*  this test is analogous to a pumping test of lim-
 ited duration.  Quantitative analysis is usually made using data obtained
 during the period of pressure buildup following the period in which the
 reservoir is allowed to flow.

    Figure 25a is a schematic DST pressure record, with a description of
 the sequence of events in a successful test.   Figure 25b is a schematic
 representation of a test in which no fluid was produced.  Conditions that
 may be encountered in a  DST are widely variable and considerable exper-
 ience may be required in order to interpret an unusual test.  The com-
 panies that provide the testing services also provide assistance in test
 interpretation.

   If a test is successful, pressure buildup data from the test are taken
 from the DST chart and tabulated.  These data are then plotted as shown
 in Figure 26.  A series of calculations of formation properties are then
 made.  The properties that are routinely calculated and are of importance
 here are:
         1. Static bottom-hole pressure

         2. Transmissivity
         3. Average effective permeability

         4. Damage ratio
         5. Approximate radius of investigation.

   The static bottom-hole pressure as  determined from a successful test
is assumed to closely represent the formation pressure at the elevation
of the pressure recording device.  Transmissivity is  average permeability
multiplied by the thickness of the  test interval.  The damage ratio is an
indication of the amount of plugging of pores in the formation during drill-
ing  of the well.  In addition to this routine information, drill-stem tests
may indicate the presence of and distance to nearby faults or facies changes
that act as barriers to flow or channels for rapid flow.

   For detailed presentations of drill-stem test analysis, the reader is
referred to Gatlin (I960),. Lynch (1962), Matthews and Russell  (1967) and
Pirson (1963).  Also, literature such as that by Murphy (undated) is read-
ily available from companies that provide drill-stem testing services.
                                  45

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ACQUISITION OF SUBSURFACE DATA
                                      Timt —•>


               X  Putting water cushion in drill pipe
               2  Running in hole
                  Hydrostatic pressure (weight of mud column)
                  Squeese created by setting packer
                  Opened tester,  releasing pressure below packer
                  Flow period, test cone producing into drill pipe
                  Shut in pressure,  tester closed immediately above packer
                  Equalising hydrostatic pressure below packer
                  Released packer
                  Pulling out of hole

        Figure 25a.  Normal sequence of events as recorded on the chart

                    during a successful drill-stem test (Kirkpatrick,  1954).
             t
                                       Time —»•


          1.  Running in hole
          2.  Hydrostatic pressure (weight of mud column)
          3.  Squeese created by setting packer
          4.  Opened tester, releasing pressure below packer
          5.  Flow period, test cone open to atmosphere
             Closed tester and equalizing hyd, pressure below packer
             Pulled packer loose
             Pulling out of hole
6.
7.
8.
          Figure 25b.  Sequence of events as recorded during a drill-stem
                      test when no fluids were produced (Kirkpatrick, 1954).
                                        46

-------
                                                             STATIC BOTTOM HOLE PRESSURE - f!
                                                                                                •0.
                                                                                             - 1160.
                                                                                             - 1140.
                                                                                                  •5
                                                                                             - 1100.
                                                                                               1080.
                                                                                                1060.
O

2
Z
o
                                                                                                                         n
                                                                                                                       >O
                                                                                                                       zz
Figure 26.  Example of a plot of data from a drill-stem test with dual closed-in periods (Murphy,  undated).
                                                                                                                       oz

-------
ACQUISITION OF SUBSURFACE DATA


   As an example of DST analysis,  data from testing of the Mt. Simon
 Formation in a well in Ohio were selected.  Figure 27 is a plot of the
 pressure buildup data for that test.  Extrapolation of the data to the
 logarithm of (t + 6)/6  = 0 shows that the static formation pressure is
 2750 psig.  The gage was at a depth of 5886 feet in the well, so the fluid
 pressure gradient is 0.467 psi per foot of depth.

    For the remaining calculations, the following values  from the test
 are needed (dimensionalized in oil field units):
         Pf  = final flow pressure = 1061 psig

         t   = final flow time = 62 min

         m  = PS "  PlO = l63 psi per log cycle
         Q  = average flow rate  =  347 bbls/day

         jj   = water viscosity =  1.065 centipoise

         b   = formation thickness = 105 ft.
    Then,
          T = transmissivity =  162.6—   (millidarcy-ft/centipoise)  (9)
                                     m
          _
          K =  average permeability = -rp-  (millidarcys)              (10)

                                0. 183(Pfl - Pf)
          DR  = damage ratio = -  (dimensionless)      (11)

                                        —  1/2
          r =  radius of investigation 2=  (Kt)      .                    (12)

     The transmissivity is computed to be 345 millidarcy-ft/centipoise, the
  average permeability 3.5 millidarcys,  the damage ratio 1.9, and the ra-
  dius of investigation 14. 73 ft.  These calculations reveal that the Mt.
  Simon Formation at this location has a very low capacity to accept in-
  jected fluids. The capacity could theoretically be improved nearly 100
  percent by removing formation damage; reservoir stimulation by hydrau-
  lic fracturing would also help, but the  reservoir is not promising.  No
  hydrologic boundaries were encountered within the  radius of investigation*
  which was only about 14 feet.  Further well testing and core analysis re-
  sults to confirm these findings are discussed in the material that follows.
                                    48

-------
                                                DURING WELL CONSTRUCTION
                                                              AND DRILLING
            2550
            2600
         Q.
          1  2650
         UJ
         QJ  2700
         tc
         Q.
         Ill
         §  2750
         O
            2800 -
                          _L
             _L
_L
~OJ    O2    OS    O4

      LOGARITHM OF t
                                           0.5
                              0.6
                                                       0.7
                                         0.8
     Figure 27. Plot of extrapolated pressure from drill-stem test data from an
               injection well in Ohio.


 Injectivity Tests
   After an injection well has been drilled and possible injection intervals
identified by coring, by geophysical logging, and by drill-stem testing,
injection tests will usually be run.  For initial injection testing, truck-
mounted pumps are often rented and treated water used for injection
rather than wastewater.   Frequently,  more than one possible injection
interval is present and tests are performed on the intervals individually
or on more than one at a time.  The common practice when performing
an injection test is to begin injection at a fraction of the final estimated
rate, to inject at this rate for at least  several hours, then to repeat this
process at increasingly greater rates  until a limiting rate or pressure
is reached.  Injection is then stopped and  the reservoir allowed to return
to its original pressure state.  Pressures may or may not be recorded
during this fall-off period.

   Regardless of the sequence in which a test is performed, if pressure,
time, and flow data are accurately recorded, and the test is run long
enough, it is theoretically possible to  analyze the test.  However,  the
simpler the test the simpler and probably  more  reliable the interpretation.
Tests performed on more than one interval at a  time are particularly
difficult to interpret and  should be avoided if possible or,  alternatively,
both single and multiple zone tests performed.
                                  49

-------
ACQUISITION OF SUBSURFACE DATA
    Figure 28 is a plot of the data from a constant.-rate injectivity test of
 the Mt.  Simon Formation.  The test was  run at 75 gpm for about 25 hours,
 The equation used to determine formation transmissivity from Figure Z»
 is:
                                                                      (13)
 Alternatively, Equation 9 can be used.  Any consistent units can be used
 in Equation 13, whereas Equation 9 is dimensionalized for oil field units
 as previously indicated.
    Using Equation 9
     162.6 X 2571bbl/day  =
x     925 psi/log cycle
     Using Equation 13

                7.  ^n x
           T =
                                            millidarcy.ft/centipoise  .
  or
     4ff X2136 ft/log cycle

T  = 9.3 gal/day ft  .
           ISOOl
                                                     • 925 pit
                 THIS PORTION OF CURVE
                 NOT USABLE FOR ANALYSIS
                             \
               O.I      I.            I                   10
                                 TIME - HOURS
        Figure 28.  Plot- of pressure buildup data from an injectivity test of the
                  Mt. Simon Formation in Ohio.
                                       50

-------
                                               DURING WELL CONSTRUCTION
                                                             AND DRILLING
    This test was run on the same well for which the drill-stem test analy-
  sis was given, but the well bore was cleaned up and acidized before the
  injectivity test, thus leading to a slightly higher transmissivity.

    The injectivity test can further be used to determine the formation stor-
  age coefficient from

              2.25Tt
          s = - — 9.     (dimensionless)
 where   to  = intercept of extrapolated test curve with time axis
          r  = radius of well bore.

    In Figure 28,  to  =  2.2 hours and

            _ 2. 25 X 1. 24 ft2/day  X 0. 0092 days  _ 0. 16

                          (0. 396)2

    As was previously discussed, storage coefficient values for confined
 aquifers are generally at least three orders of magnitude lower than the
 calculated value^of 0. 16.  As a better estimate, Equation 7 (page 27)
 yields a value for the storage coefficient of 3. 34 X 10~4. It is  believed
 that the discrepancy in this case results from the fact that the well was
 hydraulically fractured during an earlier injection test, leading to a
 greatly enlarged  effective well bore.  As an estimate of the degree of
 enlargement, Equation 14 is rearranged and solved for  r , using the cal-
 culated storage coefficient, yielding:
                1. 25 Tt
                      o
 . /
= \/
  v
               2. 25 X  1. 24 ft^/day X 0. 009 days  = g> ? ft
                                   -4-
                         3. 34 X  10 *

   This is a reasonable value and will be used in later calculations.
   If early time data are available, an alternative form of analysis that
involves curve matching can be employed.  Figure 29 is such a plot of
recovery data for an injection well at Mulberry, Florida.  The details
of the analysis of this test are given by Wilson et al. (1973).  The most
interesting aspect of this example is that the test data indicate an observ-
able amount of leakage through the confining beds.  Witherspoon and
Neumann (1972) discuss in some detail the theory and procedure for anal-
ysis of leaky confining beds and give two field examples from gas storage
projects

                                  51

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ACQUISITION OF SUBSURFACE DATA
    100
  j
  *
    10
                        I I
                                           I I
                                                      I   1  I  TT I I
                                        TRACE OF THEIS NON-LEAKY
                  Italch
                A WU,5»)»I
                  J^.I
                  WM'
                                               ARTESIAN r/B - 0.01 TYPE CURVE
                                 I
                                     I
                                       I  1  I I  I
      10
100                   1000

 TIME SINCE INJECTION STOPPED. mimiM
                                                                    10.000
    Figure 29.  Plot of recovery data and matching-type curves for an injection
              test of a well at Mulberry,  Florida (Wilson et al., 1973).
    Readers wishing to pursue the subject of aquifer testing further are
 referred to the same references previously given for drill-stem test
 analysis, particularly to the Society of Petroleum Engineers Monograph
 prepared by Matthews and Russell (1967).  Additionally, publications in
 the groundwater field by Lohman (1972) and Kruseman and De Ridder
 (1970) are excellent recent summaries of this subject, as is the refer-
 ence by Witherspoon  et al. (1967), which was prepared for the underground
 gas storage industry.
                                     52

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                              SECTION VI
                    PREDICTION OF AQUIFER RESPONSE
 FLOW THEORY
   The  basic equation used to describe the flow of fluids in porous media
is Darcy's law, alternate forms of which are given on page 25 by Equa-
tions 3, 4, and 5.  Darcy's law alone can be used for calculations of
steady flow.  Steady flow occurs when the same quantity of fluid is en-
tering an aquifer as is leaving it,  so that no change in volume of the aqui-
fer or its contained fluid is occurring with time.

   When flow is unsteady or,  as stated in oil field terminology, when for-
mation  pressures are transient, Darcy's law must be combined with the
continuity equation so that time and the compressibility of the aquifer and
aquifer fluids may be taken into account. The appropriate partial differ-
ential equation and its derivation may be found in most modern texts on
hydrogeology and petroleum reservoir engineering,  along with numerous
solutions.

   The  solution first formulated and still most widely used is that for a
well pumping from or injecting into an aquifer under  the following conditions!
         1.  The aquifer is, for practical purposes, infinite in areal
            extent
         2.  The aquifer is homogeneous, isotropic,  and of uniform
            thickness over the area of influence
         3.  Natural flow in the aquifer is at a negligible rate
        4.  The aquifer is sufficiently confined so that flow across
            confining beds is negligible
        5.  The well penetrates the entire thickness of the aquifer

        6.  The well is  small enough that storage in the well can be
            neglected and water removed from storage in the aquifer
            is  discharged instantaneously.

   This is a formidable list of assumptions,  which are obviously not com-
pletely met in any real situation.  However,  if one reviews the  character-
istics of aquifers such as the Mt.  Simon Formation,  it  can be concluded
                                 53

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PREDICTION OF AQUIFER RESPONSE
that they probably comply with the assumptions sufficiently for practical
purposes.

   The equation that describes the response of such an aquifer to a single
injection well is then:

              _J2


where


             r*S
        U = 4Tt     (dimensionless)

and      Ah = hydraulic head change at radius r  and time t
        Q  = injection rate
        T  = transmissivity
        S  = storage coefficient
        t   = time since injection began
        r   = radial distance from well bore to point of interest.

   One can easily enter the desired values into this series solution, or
tables with the series evaluated are available in the previously referenced
publications on aquifer testing.

   For large values of time, small values of radius of investigation, or
both, Equation 15 can be reduced to:

                         2. 25Tt

                           r2S

   Equations 15 and  16 are not dimensionalized; therefore, any consistent
units can be used.

   Two very important characteristics of the equations presented above
are that individual solutions can be superimposed, and that hydrologic
boundaries such as faults can be simulated by  a properly located imagi-
nary well  The fact that solutions can be superimpoWallowsfheTffects
of multiple wells  to be easily analyzed.  Because  the effect of boundaries
is analogous to that of properly located pumping or injection wells  the
existence of boundaries can be detected by observing aquifer  response to
injection or pumping or, conversely, the effects of known or  suspected
boundaries can be estimated.
                                 54

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                                                       REGIONAL FLOW
REGIONAL FLOW
   As examples of the application of Darcy's law to analysis of regional
flow, the velocity of natural flow in the Mt. Simon Formation in Ohio and
the lower Floridan aquifer in Florida will be considered.

   From Figure 18 (page 30) it can be seen that, at the location of the
Empire-Reeves injection well, the hydraulic gradient is 8 feet per mile
toward the northwest. At this location, the Mt. Simon Formation has a
permeability of 24 millidarcys (from a drill-stem test) and a porosity
of 10.4 percent (Clifford, 1973).  Rearranging Darcy's law:
        - =   . K       (L/T)
             A      aJL

where   v = apparent velocity through entire area A.

Then,
             v   _Q.   K dh                                       (18)
         v = 0 = A0  = 0
where   v = average velocity of flow through pores
         0 = porosity.

   From the data given above,  converted to consistent units, and entered
into Equation 18
v =
             21.3639 ft/yr   y   8 ft/mile
                            y
                o. 104         5,280 ft/mile
           = 0.31 ft/yr  .

   This evaluation shows that water in the Mt.  Simon Formation in north-
central Ohio is moving northwest at a rate of 0. 31 ft/yr.  The a°*rce °f
the hydraulic gradient and the fate of the moving water are not understood.
Furth'ermore^there are complications in the analysis itself, as poxnted
out by Bond (1973).  However, in spite of such uncertainties, it can be



injection site.
                                 55

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30»30'
                  •7*30'
                                                                                                               EASTERN LIMIT-
                                                                                                               BUCATUNNA CLAY
                                                                                                               CONFINING BEOS
                                                                                            JP°}0'
         6UI-F
                 of
                              CO
                       IZ HUES
            Contour shows oiiitudc of inferred     _____ Areo where soiine woter from lower
            potentiometric surfoce of the  lower   ~      Fioritfon oquifer moves upward and
            limestone ooove  mean sea level, pre-         mixes with fresh water m upper Fioridon
            1963. Contour interval. 20 feet.             aquifer  under natural conditions.

 _——looo   isochlor shows inferred chloride       °l    Fault, dashed where inferred
            concentration (milligrams per liter)       ;
            within upper port of the lower  limestone
	1	1	
                                                                                                            O
                                                                                                            n

                                                                                                            O

                                                                                                            O
                                                                                                            •n

                                                                                                            I
                                                                                                                                                m
                                                                                                                                                70
                                                                                                                                                to
                                                                                                                                                •u
                                                                                                                                                O
                                                                                                                                                •7.
                                                                                                                                                CO
                                                                                                                                                m
         Figure 30.  Hydrogeology of the lower Floridan aquifer in northwest Florida (Goolsby,  1972).

-------
                                          PRESSURE EFFECTS OF INJECTION
 The permeability is about one darcy and the porosity is estimated to be
 10 percent (Goolsby,  1971 and 1972).  The velocity of natural flow in the
 lower Floridan aquifer is then estimated to be

         v _  890 ft/yr     1.33 ft/mile  _
         v -    0>10    X 5,280 ft/mile  - Z'24 ft/yr  '

    This analysis is more easily interpreted than the previous one for Ohio,
 because it is  well known that the source of hydraulic head lies to the north
 of the injection well site and that the discharge area lies to the south as
 shown in Figure 31.  The velocity of flow is again very low; it appears
 that more than 200, 000 years would be required for injected waste to
 reach the  subsea discharge point 100 miles to the  south.


 PRESSURE EFFECTS OF INJECTION
    Wastewater injected into  deep aquifers does not move into  empty  voids;
 rather it displaces existing fluids, primarily saline water.  The displace-
 ment process requires exertion of some pressure, in excess of the natural
 formation  pressure.  The pressure increase is greatest at the injection
 well and decreases in approximately a logarithmic manner away from the
 well.  The amount of excess pressure  required and the distance to which
 it extends  depend on the properties of the formation and the fluids, the
 amount of  fluid being injected,  and the length of time that injection has
 been going on.  The pressure or head changes resulting from injection
 are added  to the original regional hydraulic gradients to obtain a new po-
 tentiometric surface map that depicts the combined effects of regional
 flow and the local disturbances.

   By use  of the theory that has been described, potentiometric surface
 maps can be produced to  show the anticipated situation at any time in the
 future.   If observation wells exist, the actual potentiometric surface at
 any time can be constructed  from the water levels  or pressures  recorded
 in the wells.

   Figure  32 shows  the theoretical potentiometric  surface map for the
 lower Floridan aquifer in northwestern Florida in  1971, after wastewater
 injection had been in progress near Pensacola for  about eight years.  The
 estimated pressure  effects of injection can be  seen by comparing Figure 30
with Figure 32.  The comparison indicates that changes in hydraulic  head
may extend out for 30  miles or more from the  injection site.  Although
 Figure 32 is titled a theoretical potentiometric surface map, it is, in
fact, partially substantiated by observation wells.  If more observation
wells were available,  the map would be constructed entirely from observed
data.
                                 57

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  500*
 SEA
LEVEL
                                                                                     LOCATION  MAP

                    ABOUT  100  MILES  TO DISCHARGE AREA 	»-j-«-ABOuT 75 MILES TO RECHARGE AREA
                                                                                                          BOO
                                                                                                          2000
                                                                                                          2500'
                                                                                                          3000
3500*
              O
              n

              6

              §
              >
              D

              Tl
              m
                                                                                                                       3
    Figure 31.  Generalized north-south geologic section through southern Alabama and northwestern Florida
               (Goolsby,  1972).

-------
3i»OO  _
 SO»SO' -
                                                                                                                 EASTERN LIMIT.
                                                                                                                 BUCATUMNA CLAY
                                                                                                                ,r CONF1NINC BCD
                                                                                                                                  Si'OO
                                                                                                                                -SO»X
12 MILES
                                               Contour show oltitude of theoretical   ~///t_ Areo where saline woler from lower
                                               potentiometric «urfoce of the tower            Fioridon aquifer moves upward and
                                               limestone  in feet above  meon sea level,
                                               lote 1971.  Contour interval, 20 feet.
                                     --- iboo  Iscchlor shows inferred  chloride
                                               concentration (milliarams per liter)
                                               within upper port of the  lower limestone.
                                                                                           mixes with fresh water m upper Fioridon
                                                                                           aquifer under natural conditions.
                                                                                      MU   c  •.  ^   t ^ _^    •  .
                                                                                      T   Fou" • dothed «**rt inf«"««»-
                                                                                                                                                   m
                                                                                                                                                   CO
                                                                                                                                                   CO
                                                                                                                                                   m
                                                                                                                                                   •n
                                                                                                                                                   -n
                                                                                                                          CO
                                                                                                                          o
Figure 32.  Theoretical potentiometric surface of lower limestone of F lor I dan aquifer in late  1971  (Goolsby,  1972).
                                                                                                                                                   O

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PREDICTION OF AQUIFER RESPONSE


   As an example of the development of such a theoretical potentiometric
surface map, one point on Figure 32 will be determined.  The point will
be one at a radial distance of 6 miles northeast of the injection well site,
which places it at a potential of about 77 feet on Figure 30 and 180 feet on
Figure 32, showing a head increase of about 103 feet.  From Goolsby (19?Z)»
the following data were obtained or estimated:

        Q = 2.427 X  106 gal/day = 3. 244 X  105 ft3 /day
        T = 6,300 gal/day ft = 842 ft3/day ft
        t  =3, 000 days

        r  = 6 miles =  31,680 ft

        S  = 2 X 10"4  (dimensionless)  .

   Therefore, from Equation 16, the head increase in  3,000 days 6 miles
northeast of the injection site is:

        Ah = 2.30X  3.244  X IQ5 ft3/dav
                 4ff x 842 ft3 /day -ft

              X inC 2'25 X  842 ft3/day-ft X 3,000 days
                         (31,680ft)2 X 2 x 10"4

              = 70.50 log 28.31 = 102.4ft  .

   The calculated increase of 102. 4 feet compares very well with the 103
feet obtained from Goolsby's maps.  As many points as desired can be
       I   - Pfr,°d*CMhe contour «**•  Rather than calculating the pres-
          °    aCU     °n a CirClC Wi*h radius  r > even hea* increments
                      radii to
                                                 , and for which a
         e                   **" ™° P"«nted,  will also be used as
           t   dr^re,   .a yiC,lded * tranami"^ty of 954 millidarcy-ft/
           Si    vfem t6/* 345 ^^a^y-ft/centipoise, and the in-
           4"dimhllldarcy:ft/c^ipoise..  The value from the injection


               asrr.-a: ? s

                                60

-------
                                            PRESSURE EFFECTS OF INJECTION
          i   *   4ff T Ah    log 2.25T
          10* * = T30Q  -     2q
                              r  o


          .   A   (4ff) (1.24 ft2/day) (4157ft)       (2.25) (1.24 ft2/day)
          log t = J—u	"-4       - log      ^r          ^4
                    (2. 30) (14,437 ft3/day)         (8. 7 ft)* (3. 34 X 10  )

          log t = 1.95 - log 110.36 = -0.092
             t= 0. 81 days = 19.4 hours.

 This value could also have been obtained by extrapolating to 1800 psi the
 line in Figure 28 (page 50),  but only for the same injection rate and radius
 of investigation and not for other rates  and radii.

   As the injection rate is changed the amount of time required for the
 pressure to increase to a  particular level changes proportionately,  so
 that for an injection rate of 50 gpm,  t = 27 hours, and for an injection
 rate of 25 gpm, t = 54 hours.

   For this well, the calculations simply confirm what could already have
 been intuitively deduced; the fact that the Mt.  Simon Formation will not
 be a suitable injection unit at this location.  Similar calculations could
 have been made from core data and from the drill-stem test and this con-
 clusion reached prior to injection testing.

   In comparison with the  Ohio example, a well in northern Illinois had
 the following characteristics:

         b     =  1734 ft
         K     =36 millidarcys
          av.
         T     =  62.42 darcy'ft

         Q     =  100 gpm

         rwell = 4-4in'
         S    = 5.46 X 10'3  .

   Using these data, what  will be  the injection pressure increase at the
well after 5 years of continuous operation?

                       lf F2.30  X  19. 248 ft3/day
        Ap = 0.433 psi/ft  —        	"	
                              4ff x  167 ft2/day

                     2.25 X  1825 days X 167 ft2/day
                X log	o	        ^3
                       (0.36 ft)  x 5.46 X 10
= 81 psi
                                 61

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PREDICTION OF AQUIFER RESPONSE
   This calculation shows that the pressure increase will be negligible.
In actual operation,  the injection pressure has averaged 120 to 300 psi;
the difference between predicted and observed performance is not of
concern in this case unless the observed pressure continues to increase,
indicating possible progressive plugging of the formation.

Multiple Wells

   As previously mentioned, estimating the combined pressure effects
of multiple wells is made easy by virtue of the principle of superposition.
It is only necessary to estimate the separate effects of two or more wells
at the point of interest, then to add them to obtain their combined effect.
For example, referring to the last Mt. Simon well discussed above, what
would the combined effects  of two wells spaced 1,000 feet apart be on
each other after 5 years?  Assume both wells have the same character-
istics:

         Ap = 81 psi + 0.433 psi/ft I"2'30* 19, 248 ft3/day
                                   L 47T X 167 ft2/day

                             X log 2'25 *  1825  x  I67ft2/dav1
                                   (1000ft)2 x 5.46  x  10"3 J

         Ap = 81 psi + 19  psi = 99 psi .

Hydro logic Discontinuities

   Another common situation is one in which a barrier to flow  a fault or
facies  change, is present within the area of influence of an injection well.
Faults may also act as channels for escape of fluid from the injection
horizon.

   In predicting aquifer response in the presence of such features, the
image-well concept is used. Assume the presence of a fault or lithologic
change that acts as an impermeable barrier, 500 feet in any direction
from the Mt. Simon Formation injection well that is discussed above
Then  according to image-well theory, an imaginary injection well with
all of the same properties as the real injection well is placed 1,000 feet
from the real well, on the opposite side of the fault and on a line that
passes through the real well and is perpendicular to the fault.  Figure 33
shows the potentiometric  surface and flow lines that would develop in such
a situation; the pressure effect of the barrier would be the same as that
calculated above for an actual injection well 1, 000 feet from the first well.

   If the hydrologic discontinuity were a leaky fault rather than a sealed
one, the opposite effect would occur; the pressure at any time would be
reduced as if a discharging well were present.

                                  62

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Figure 33.  Generalized flow net showing the potential lines and stream lines in the vicinity of an
           injection well near an impermeable boundary (Ferris et al.,  1962).
                                                                                                              CO
                                                                                                              CO


                                                                                                              73
                                                                                                              m
m
n
CO

O


z
c_
rn
                                                                                                              O

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PREDICTION OF AQUIFER RESPONSE
   The equations and examples given are for the most basic hydrogeologic
circumstances, but many injection wells can be treated this way because
these are the conditions sought when choosing an injection site and re-
ceiving aquifer.  However, cases of virtually any complexity can be ana-
lyzed by use of the appropriate solution to the basic flow equations; where
analytical solutions are not possible, numerical models can be developed.
The limitations to an analysis are usually pragmatic rather than theoretical
-lack of data,  limitations of time and funds, or the fact that a simplified
estimate is sufficient for the circumstances.

RATE AND DIRECTION OF FLUID MOVEMENT

   As with pressure response to injection, the rate and direction of move-
ment of the injected fluid depend on the hydrogeology of the site; therefore,
the same factors previously listed require consideration.  In addition, the
properties of the formation water and the injected wastewater assume major
importance.

   Broad flow patterns in an aquifer with a significant existing potentio-
metric gradient can be deduced from a map of the regional potentiometric
surface with the effects of the injection  system superimposed.

   Figure 34 is a duplication of Figure 32, with flow lines added to show
how the flow directions of aquifer water and injected wastewater can be
deduced from the potentiometric surface map.  The wastewater will never
actually travel as far northward as  the map indicates, but displaced aquifer
water will be forced in this direction, ahead of the small cylinder of waste-
water that surrounds the well.  The extent of this wastewater cylinder will
be discussed next.

   A good estimate of the minimum distance of wastewater flow from an
injection well can be made by assuming that the wastewater will uniformly
occupy an expanding cylinder with the well at the  center.  The eauation
for this  case is:                                             H
         r =                                                       (19)

 where   r = radial distance of wastewater front from well
         V = Qt  =  cumulative volume of injected wastewater
         b = effective aquifer thickness
         0 = average effective porosity.
                                   64

-------
 3i •00'
ALABAMA
                             •-x«P  (  INJECTION SITE.
                                                                                                          EASTERN LIMIT.
                                                                                                          aUCATUNNA CLAY
                                                                                                          CONFINING KO
                                                                   EXPLANATION
                        12 MILES
                                        	1000
Contour shows oltitude of theoretical
potentiometric surface of the tower
limestone in  feet above mean sea level.
tote 1971. Contour interval, 20 feet.
Iscchlor shows inferred chloride
concentration (milligram* per liter)
within upper port of the lower limestone.
                            Area where saline water from lower
                            Fioridon aquifer moves upward and
                            mixes with fresh water in upper Fioridon
                            aquifer under natural conditions.
                            Fault, dashed where inferred.
                                                                                                                          JO»JC
                                                                                                                                       Si
Figure 34.  Theoretical potentiometric surface of lower limestone of Floridan aquifer in fate 1971, with flow lines show-
             ing the directions of aquifer water and wastewater movement.  Solid flow lines show the direction of flow of
             diverted aquifer water, dashed flow lines show direction of flow of injected wastewater and displaced aquifer
             water (modified after Goolsby,  1972).                                                                     H
                                                                              ^W. • ••
                                                                              m O

                                                                              SO

-------
 PREDICTION OF AQUIFER RESPONSE


  For a Mt.  Simon injection well with the following characteristics:
        Q  =  100 gpm
        t  =  5 years
        b  =  1618 feet
        0  =  13.5 percent
                  35,128,993 ft3
                  X 1618 ft X  0. 135

           =  226 ft  ,

   It is noted that effective aquifer thickness and average effective porosity
should be used.   The effective aquifer thickness is, for example,  that part
of the total aquifer that consists of sandstone in the case of a mixed
sandstone-shale lithology.  The effective porosity has been previously
defined as that part of the porosity in which the pores are interconnected.

   In most situations the minimum radial distance of travel will be ex-
ceeded, because of dispersion,  density segregation, and channeling through
high permeability zones. Flow may also be in a preferred direction,  rather
than radial, because of hydrologic discontinuities (e.g., faults), selectively
oriented permeability  paths, or natural flow gradients.

   An  estimate of the influence of dispersion can be made with the follow-
ing equation:

         r'  = r  + 2.3/Dr"   (L)                                    (20)

where   r'  = radial distance of travel with dispersion

         O  = dispersion coefficient; 3 ft for sandstone aquifers and
              65 feet for limestone or dolomite aquifers.

    Equation 20 is obtained by solving  equation (10.6.65) of Bear (1972)
 for the radial distance at which the injection front has a chemical concen-
 tration of 0. 2 percent of the injected fluid.

    The detailed development of dispersion theory is presented by Bear
 (1972).  The dispersion coefficients given are high values for sandstone
 and limestone aquifers  obtained from the literature. No actual dispersion
 coefficients are known to have been obtained for any existing injection
 well.
                                  66

-------
                                                   RATE AND DIRECTION
                                                   OF FLUID MOVEMENT
    Then, for the above example,  which is a sandstone:
         r' = 226 ft + 2. 3 /3ft X  226 ft

            = 286 ft  .

   It is clear that, in this example, the distance of wastewater travel
 from the well is negligible and could not possibly be of concern if actual
 conditions comply even generally with those that were assumed.  This
 conclusion has been found to apply to many of the wells that have been
 constructed to date.  Since almost no attempts have been made to deter-
 mine the actual wastewater distribution around existing injection wells,
 there is little evidence for comparison with theory.  However, if such
 a calculation were in error by several hundred percent,  there would still
 be no cause for concern, since the injection well,  in this and many other
 cases,  is tens of miles from the nearest other well penetrating the injec-
 tion zone.

   To proceed beyond the calculations that have been  shown may not be
 necessary or,  in many cases,  meaningful. However, it  may be possible,
 if necessary,  to account for some of the additional complications that
 are mentioned.   For example, Bear and Jacobs (1964), in one of a  series
 of reports, considered the flow of water from a groundwater recharge
 well in an  aquifer of uniform flow, when the densities and viscosities of
 the injected and interstitial fluids are the same.  Gelhar and others (1972)
 developed  analytical techniques for describing the mixing of injected and
 interstitial waters of different densities.

   So far,  the travel of the injected wastewater has been treated as though
 it were an inert fluid and would not react with the aquifer water or minerals,
 be affected by bacterial action, or decompose or radioactlvely decay.  If
 the wastewater is not inert,  then changes in chemical composition with
 time and distance may also need to be considered.  Bredehoeft and Finder
 (1972) discuss the methodology for a unified approach to  this type of prob-
 lem and Robertson and Barraclough (1973) presented an example of a case
 in which radioactive decay, dispersion,  and reversible sorption were con-
 sidered. However,  no procedure exists  at this time for  simultaneously
 considering the full range of practical possibilities that may be involved
 in wastewater movement.

   In spite of the degree of sophistication used in development of theories
for  rate and direction of travel of injected fluid from an injection well,
nonuniform distribution of porosity and permeability will preclude making
accurate estimates in many cases.  In general, wastewater flow in unfrac-
tured sand or sandstone aquifers would be expected to more closely agree
                                  67

-------
PREDICTION OF AQUIFER RESPONSE
with theory than flow in fractured reservoirs or in carbonate aquifers
with solution permeability.  However, even in sand aquifers, flow can
be expected to be non-ideal as shown by tests reported by Brown and
Silvey (1973).  Particularly great deviations from predictions may occur
in limestone or dolomite aquifers. Figure 35 is an example of this.   The
radial zones around Well No. 1 show the predicted extent of waste travel
using Equations 19 and 20.  The irregular boundary shows the probable
actual extent of wastewater spread as indicated by evidence from Wells 2
and  3.  In this case, the wastewater apparently traveled selectively in a
single thin porous and permeable interval rather than throughout the sev-
eral zones indicated by testing results.  Accurate prediction of the rate
and  direction of movement in such a case may well be technically infeas-
ible even in the future because the amount of information needed will  sel-
dom, if ever,  be  available.


HYDRAULIC FRACTURING     tt  f^ORO - Ffcf\
-------
                                                   HYDRAULIC FRACTURING
 pf damage to well facilities and because of the uncertainty about where
 the fractures and injected fluids are going as fractures continue to be
 extended.

    Figure 36 is a schematic diagram of bottom-hole pressure versus time
 during hydraulic fracturing. Before injection begins, the pressure is that
 of the formation fluid (po) and the column of fluid in the well bore.  Pres-
 sure is increased until fracturing occurs;  then,  as  fluid continues to be
 pumped into the well, the pressure stabilizes at pf, the flowing pressure,
 during which the fractures continue to be extended.  When injection is
 ceased, and the well shut in, the pressure quickly stabilizes  to a constant
 value,  the instantaneous shut-in pressure. This pressure is considered
 to  be equal to the least principal earth stress in the vicinity of the well.

    In estimating the fluid pressure at which hydraulic fracturing will occur
 one of two conditions is usually assumed:

          1.  That the least principal stress is less than the vertical
             lithostatic stress caused by the rock column.  In this
             case fractures are assumed to be vertical.

         2.  That the vertical lithostatic stress is the least principal
             stress. In this case fractures will be horizontal.

    In the first case, the minimum bottom-hole pressure required to ini-
 tiate a hydraulic fracture can be estimated from (Hubbert and Willis, 1972):

              S  +  2p           ,
         p. *  Z   3 °     (F/LZ)


 where   pj = fracture initiation pressure
         Sz = total lithostatic stress
         P0 = formation fluid pressure.

    The  fracture gradient, that is,  the injection pressure required per foot
 of depth,  can be estimated by entering representative unit values into
 Equation 21.  The unit  values for Sz and po  are, respectively, 1.0 and
 0.46 psi/ft.  This yields a Pi gradient of 0. 64 psi/ft as a minimum value
 for initiation of hydraulic  fractures.  This  situation implies a minimum
 lateral  earth stress. As the lateral  stresses increase, the bottom-hole
 fracture initiation pressure also increases up to  a limiting value of 1. 0
pfli/ft.  Actually,  fracture pressures may exceed 1. 0 psi/ft when the rocks
have significant tensile strength and no inherent fractures that pass through
the well bore.  In any particular case,  injection tests can be run to deter-
mine what the actual fracture pressure is,  then operating injection pres-
 sures held below the instantaneous shut-in  pressure. In the absence of any

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PREDICTION OF AQUIFER RESPONSE
 ID
 ft.


9000
2000
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s
      "          »            10            »           »           U
                                TIME - MINUTES
     Figure 36. Schematic diagram of pressure versus time during hydraulic
              fracturing (Kehle, 1964).

specific data, arbitrary limitations of from 0. 5 to 1.0 psi per foot of depth
have been imposed on operating injection wells.  Regional experience should
be used as a criterion in establishing an arbitrary limit, since regional tec-
tonic conditions  and fluid pressure gradients dictate what a  safe limit will be,

GENERATION OF EARTHQUAKES

   As a matter of background, it is widely, but not universally, accepted
that a series of  earthquakes that began in the Denver area in 1962 was
initiated by  injection of wastewater into a well at the Rocky  Mountain Ar-
senal. Since the association of seismic activity with wastewater injection
at Denver,  apparently similar situations have been observed at Rangely,
Colorado, and Dale, New York.  The former related to water injection
for secondary recovery of oil and the latter to disposal of brine from so-
lution mining of salt.  On the other hand, there are presently about  160
operating industrial wastewater injection wells and tens of thousands of
oil field brine disposal wells that have apparently never caused any  notice-
able seismic disturbance,  so these three examples would have to be con-
sidered very rare.
                                  70

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                                        GENERATION OF EARTHQUAKES
   It has been erroneously stated by many that the seismic events have
been stimulated by "lubrication" of a fault zone by injected fluids.  What
has happened, if injection has been involved, is that the water pressure
on a fault plane has been increased, thus decreasing the friction on that
plane and allowing movement and consequent release of stored seismic
energy.

   Based on this interpretation of the mechanism of earthquake triggering
by fluid injection,  some of the conditions that would have to exist in order
to have such earthquakes would be:
         1.  A fault with forces  acting to cause movement of the blocks
            on either side of the fault plane, but which are being suc-
            cessfully resisted by frictional forces.
         2.  An injection well that  is constructed close enough, verti-
            cally and horizontally, to the fault so that the fluid pressure
            changes  caused by injection will be transmitted to the fault
            plane.
         3.  Injection at a sufficiently great rate and for a sufficiently
            long time to increase fluid pressure on the fault plane to
            the point that frictional forces resisting movement become
            less than the forces tending to cause movement.  At this
            time, movement will occur and stored seismic energy will
            be released. That is, an earthquake will occur.

   As has been discussed earlier in the  section on state of stress, rela-
tively little is known  about stress distribution in the earth's crust and
even less is known about stress distribution along fault systems.  In the
absence of this information, only qualitative estimates of the probability
of earthquake stimulation can be made.  In the great majority of cases
the potential for earthquake stimulation will be nonexistent or negligible
because only very limited areas in the country are susceptible to earth-
quake occurrence.  The susceptible areas are delineated by records of
earthquakes that have occurred  in the past and by tectonic maps that show
geologic features which are associated with belts of actual or potential
earthquake activity.

   In a case where  subsurface stresses are known or are determined by
hydraulic fracturing or other means, and where  the location and orienta-
tion of the fault plane are known, then a quantitative estimate of the pres-
sure required to cause fault movement can be made.  Raleigh (1972) pro-
vides an example of such a calculation from the Rangely, Colorado, oil
field.
                                 71

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                             SECTION VII
                  SURVEILLANCE OF OPERATING WELLS
INJECTION WELL MONITORING
   The principal means of surveillance of wastewater injection that is
presently practiced is monitoring at the injection well of the volume,
chemistry, and biology of the injected wastewater and of the well-head
and annulus pressures (Figure 37).  To some this apparently seems in-
adequate.  However,  if all of the necessary evaluations have been made
during the planning,  construction, and testing of the well,  then this may
be a satisfactory program when combined with periodic inspection of
surface and subsurface facilities.  This is because, as pointed out by
Talbot (197Z), the greatest risk of escape of injected fluids is  normally
through the injection well itself,  rather than from leakage through per-
meable confining beds,  fractures, or unplugged wells.

   The purpose of monitoring the volume  of injected wastewater is to
allow for estimates of the distance of wastewater travel, to allow for
interpretation of pressure data, and to provide a permanent record of
the volume of emplaced wastewater.  Also, a record is needed as evi-
dence of compliance with restrictions, for interpretation of well behavior,
and as a precaution in the event that a chemical parameter should deviate
from design specifications,   Some characteristics that have been moni-
tored continuously are suspended solids,  pH, conductance, temperature,
density, dissolved oxygen, and chlorine residual.  Complete chemical
analyses are frequently made on a periodic basis on composite or grab
samples.  Because bacteria may have a damaging effect on reservoir
permeability, periodic  biological analysis of some wastewaters may be
desirable to insure that organisms are not being introduced.

   Injection pressure is monitored to provide a record of reservoir per-
formance and as evidence of compliance with regulatory restrictions.
Injection pressures are limited to prevent hydraulic fracturing of the
injection reservoir and confining beds, or damage to well facilities. As
with flow data, injection pressure should  be continuously recorded.

   Pressure fall-off data collected after any extended period of continuous
operation can be used to check the performance of the reservoir as com-
pared with is original condition.  However, it should be noted that the
                                  72

-------
                                             INJECTION WELL MONITORING
G
                                                  PRESSURE GAGE
                                                  WELLHEAD PRESSURE

r
FRESH-WATER-BEARING - —*••"-" — ™ —
SURFACE SANDS AND o . . ' o '.•
GRAVELS • « '. ' • o
— *" ..'•'.' o.
o • ° . •.«•<>
^"v_ - •-.-
IMPERMEABLE SHALE ' — -• _

• ' • * •
CONFINED FRESH-WATER-, .
BEARING SANDSTONE ... ' •
"' . .
IMPERMEABLE ~"JU 	 — -~
SHALb V "' "" * —- - - ^^T"
\ — — 	 —


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s

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'•"~" — *~*^ — "
	 	 - "
PERMEABLE SALT-WATER- .''-.••'..
BEARING SANDSTONE •.•'/.-. ,
INJECTION HORIZON ',.,.•,, . ' .
l^s
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" *"..'•• ';"-' : ;.'• "•'•'• ' •
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={l} PRESSURE GAGE O psi
^
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-=~ SURFACE CASING SEATED
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INNER CASING SEATED IN OR



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-—- 	 	
_ , - — . — —
,r^ INJECTION TUBING
— ANNULUS FILLED WITH
--*" NONCORROSIVE FLUID
"=- PACKERS TO PREVENT FLUID
^CIRCULATION IN ANNULUS
OPEN-HOLE COMPLETION IN
	 ' COMPETENT STRATA
' \; ' ' •''. .'. ' ', '• .'

 IMPERMEABLE SHALE
Figure 37.  Schematic diagram of an industrial waste injection well completed
           in competent sandstone (modified after Warner,  1965).

-------
SURVEILLANCE OF OPERATING WELLS
time scale of continuous recorders is not generally adequate for providing
data during the early period of a pressure fall-off test,  so the continuously
recorded data will probably need to be supplemented with additional ob-
servations in order to have a complete record of the test.

   Figure 28 (page 50) is an example of the pressure response that would
ideally be expected during a period of continuous injection.  Pressure in-
crease through time should be  linear on a semilogarithmic scale,  after
an early period of adjustment.

   In contrast with this ideal behavior, Figure 38 shows the injection
pressure history of a wastewater injection well completed in a carbonate
reservoir.  Two  marked periods of pressure decline are shown, one in
1967-1968  and one in 1970. The explanation for this is  believed to be that
the wastewater being injected,  initially an acid solution, reacted with the
carbonate reservoir to increase the permeability and thus decrease the
injection pressure.  The period of gradual pressure increase during  1969-
1970 is  probably  the normal buildup following this initial period of perme-
ability increase.  In 1970, the  wastewater composition was changed to in-
clude a second acid stream. This new stream apparently caused additional
permeability increase and a temporary reduction in injection pressure,
after which the expected pressure buildup resumed.

   Figure 39 shows the plots of two pressure fall-off tests performed in
an injection well  of the Monsanto Company, Pensacola,  Florida.   This
well is also constructed in a carbonate aquifer.  One test was made in
   800
   600
   400
    200-
          IM7         (966           1969           1970         1971
                                  YEAR


    Figure 38. Pressure history of a well injecting into a carbonate aquifer.
                                    74

-------
                                            INJECTION WELL MONITORING
  UJ
  Ul
  u.
     60
    100
    120
    140
    160
  ac
  ui
    180
    200
                      JAN. 1969
                   /O a 975 gpm
                   o
          NOV I967/
         0 * 950 gpm
                      to
     100
TIME, MINUTES
1000
10,000
       Figure 39.  Semi logarithmic plot of rwo pressure fall-off tests measured
                 in an injection well of the Monsanto Compart/,  Pensacola,
                 Florida (Goolsby,  1971).

 November 1967, before injection of an acidic wastewater  stream began.
 The other test was performed in January 1969, after the acidic wastewater
 had been injected for nine months.  The second test shows a much slower
 rate of fall-off, indicating an increased permeability in the vicinity of the
 well bore caused by  reaction of the acidic wastewater with the carbonate
 aquifer.  This conclusion is substantiated by an increase in the injection
 index for this and another well during the same time period, as shown in
 Figure 40.

   Some other possible causes of deviation from the ideal response are
 the presence of hydrologic barriers of conduits, leaky confining beds,
 and permeability reduction from  suspended solids, chemical reactions,
 etc.  The variety of factors that may influence well behavior indicates
 the need for maintaining an accurate, detailed well history so that the
 probable cause of any unusual performance  can be deduced and the ap-
 propriate action taken.

   Pressure in the casing-tubing  annulus is monitored to detect any changes
that might indicate leakage through the injection tubing or the tubing-casing
packer.  When a packer is used,  the casing-tubing annulus pressure should
be zero, except perhaps for some pressure  resulting from expansion of
                                  75

-------
SURVEILLANCE OF OPERATING WELLS
    16


    16


2   l4

    12


    10


    8
               INJECTION INDEX •     "if* *"* """
                              I/2(AP A + AP "8")

               AP » BOTTOM - HOLE PRESSURE INCREASE
            1963
                 1964
1965
1966
1967
1968
1969
    Figure 40.  Monthly average injection index of two injection wells of the
              Monsanto Company, Pensacola, Florida (Goolsby, 1971).

 the injection tubing.  In cases where a packer is not used, pressure will
 be exerted directly on the fluid in the annulus,  and indication of leakage
 would be a significant change in the annulus pressure.

    Other methods of monitoring of the injection well also deserve mention.
 The corrosion rate of well tubing and casing may be monitored by use of
 corrosion coupons inserted in the well. A conductivity probe may be
 used to detect a change in the chemistry of the fluid in the casing-tubing
 annulus.  In wells with packers the conductivity probe can be used to  de-
 tect tubing leaks, and in wells without tubing to detect shifts in the inter-
 face between the injected fluid and the casing-tubing fluid.  Another tech-
 nique that has been used to monitor the casing-tubing annulus is continuous
 cycling of the annulus fluid and analysis of the  return flow for evidence of
 contamination by wastewater.


 PERIODIC INSPECTION AND TESTING

    Sufficient incidents  have occurred in the past to emphasize the need
 for periodically  inspecting or testing the subsurface facilities of injection
 wells, particularly when chemically reactive wastes are being injected.
 One such incident was  the rather spectacular failure of a wastewater in-
 jection well at the Hammermill Paper Mill,  Erie,  Pennsylvania.  In  that
                                    76

-------
                                          PERIODIC INSPECTION AND TESTING
 instance, the well casing parted as a result of corrosion and a portion of
 it was reportedly lifted from the hole by fluid pressure.  Substantial loss
 of wastewater into Lake Erie and abandonment of the well resulted.  Other
 cases have been  reported in which portions of tubing or casing have failed
 by corrosion and caused temporary or permanent shutdown of the well.
 There may also be reason to examine the well bore to check for the loca-
 tion of zones of wastewater entrance, enlargement due to chemical reac-
 tion, the location and orientation of induced fractures,  buildup or precipi-
 tates or filtered  solids,  etc.  Examples are available of wells that have
 been abandoned or modified because of borehole enlargement that led to
 collapse of the borehole or damage to the casing or cement near the bot-
 tom of the casing string.

    Methods of inspection of casing, tubing, cement and the well bore are:

         • Pulling of tubing and visual or instrumental  inspection

         • Inspection of casing or tubing in place, using magnetic logs

         • Inspection of casing, tubing, or the well  bore with caliper
           or televiewer logs

         • Pressure testing of casing
         • Inspection of casing cement with cement  bond logs
         • Inspection of casing, cement, or the well bore with injec-
           tivity or temperature profiles or other appropriate logs.

   The process of pulling and inspecting tubing is self-explanatory.  Me-
 chanical methods are available, for example,  for inspection of lined steel
 tubing for flaws in the lining.  Individual joints of tubing can be pressure
 tested at the surface for leakage.

   Magnetic down-hole casing or tubing inspection services are  provided
 by oil field service companies.  These logs indicate, by virtue of the elec-
 tromagnetic response of steel pipe, the relative pipe thickness.   Thin
 areas may indicate corrosion or other damage.  If such a log is run early
 in the life of the pipe, then logs run after the well has been in operation
 are much more easily interpreted.  Figure 41 shows the response of a
 pipe inspection log and photographs of the casing that was pulled after
 running the log.  Figure 42 is a portion of a pipe inspection log from a
 wastewater injection well which indicates possible corrosion in the  inter-
 val from 1480 to 1510 feet; regular deflections on the log represent casing
 joints.  Corrosion could either be on the inside or the outside of the casing.

   Caliper logs provide a record of the inside diameter  of pipe or bore-
hole walls and may show intervals of pipe corrosion, borehole enlarge-
ment, or  borehole plugging at the formation face. Figure 43 shows
                                  77

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SURVEILLANCE OF OPERATING WELLS


      PHASE SHIFT       PHASE SHIFT
   0°             360°  0°              100
     f M I  I  I  I  I I  I
    JOMt '19-fcltOT 3' MWffl*CmM
    Mth siMral MUD hota.
    tort '20-MtM tao ftwft rf tort
    wtrtly coirodtd with wwil l(i|t
    koto 1" to 2" « duMttr. (OHM 2'
    hn MttMiw cvroiiOT «Hk i
           I I  I  I  t=4=i
    IOMI'21 - SMMMy cvraM ww tap
    tao ft** of**
       i
       Figure 41. Pipe Inspection Log and photographs of casing pulled after
                 log was run to verify the log (Schlumberger, 1970).

 portions of a caliper log run before injection and after 5 years of injection
 of an acidic wastewater into  a limestone  aquifer.  The log indicates con-
 siderable borehole enlargement as a result of dissolution of the limestone
 by the injected acidic waste in the interval from 1500 to 1600 feet.  It
 would be reasonable to conclude that most of the wastewater entered that
 interval.

   Borehole televiewers provide an image of the pipe of borehole wall
 as produced by the reflection of sound waves emitted from a sonde.  The
 combination sound source and receiver is highly directional and is ro-
 tated rapidly as the tool  is moved up the  hole.  Thus, the hole is contin-
 uously scanned. The resulting information is displayed on an oscilloscope
 and a film made of the scope display. The picture obtained depicts the
 well bore as though it were split open and laid out for inspection.  Figure
 44 illustrates the detail with which the borehole televiewer can indicate
 casing damage.  In Figure 45 vertical fractures in the borehole wall of
 a well in Oklahoma are shown.

   Pressure testing can  be used to detect casing leaks and it is required
 by law in many oil-producing States as a method of testing the integrity
 of casing in new wells at the time that the casing is cemented into the
 borehole.   In such tests, a cement plug is left at the bottom of the cas-
 ing during cementing and allowed to harden.  The interior of the casing
                                   78

-------
                                        PERIODIC INSPECTION AND TESTING
       Bl
  1400'
         -I	'	-\  DECREASING CASING
                       THICKNESS
                                                    =*•
               ~^L  (1 division - 0.0084 in.)  1
 1500'
                                  POSSIBLE
                                  CORRODED i
                                  ifciTr?r»w A i   T
Figure 42.  Portion of a casing inspection log run in a wastewater injection
          well showing possible corrosion in the interval from 1480 to
          1510 feet.
                               79

-------
SURVEILLANCE OF OPERATING WELLS
             July  1966
                    September  1971
    1400
    1500
     1600
UJ
UJ
UJ

«r
en
o
|   1700
UJ
m
0.
UJ
O
     1800
     1900 L
                                             1400
                                             1500
                                             1600
                                                                 1700
                                             1800
                                                    UJ
                                                    UJ
                                                                        UJ
                                                                        or
                                                                        en
                                                                        o
                                                     1
                                                     UJ
                                                     OD
                                                     o.
                                                     UJ
                                            JI900
             t
16
0  8 12 16  20 24   28
                                                          36
        DIAMETER, IN INCHES
                DIAMETER, IN INCHES
     Figure 43.  Preinjectlon and postlnjection caliper logs from a wastewater
                injection well at Belle Glade, Florida, showing solution of
                the limestone aquifer in the 1500- to 1600-ft interval by
                acidic wastewater (Black, Crow, and Eidsness, 1972).
                                    80

-------
                                            PERIODIC INSPECTION AND TESTING
                    BOREHOLE TELEVIEWER
                         -:-.-:!•.•.::;:• .;••/:•:
l^f:l|[l';G;£:Sl|r:;s'!:;|l:
-- ."-jjijy1-;, :•.•.::-." •••":••.'::':''• :.•;'•";--.•;-.•:;•,
.. - &".:.•: . .:•' '.' V.-;y>.-:;•'.> >:"
 ilf^iil
                       •«;; :.*:
              4465-
                                            PERFORATIONS
                                            4 SHOTS/FT.
                                            PHASED 120°

                OLD PACKER SEAT
                (DRILLED OUT)
                                            CASING COLLAR
                     CASING INSPECTION

         Figure 44. Borehole televiewer log of a section of casing showing
                   casing perforations, packer seat, and casing collar
                   (Schlumberger,  1970).

is then subjected to a specified amount of fluid pressure  (0. 2 psi per foot
of casing in Texas). * Rapid decline in pressure indicates leakage from
the casing.  Such a test could also be performed periodically in operating
wells by setting temporary plugs or using  packers.

   The cement-bond log is used to determine the quality of the casing -
cement bonding and to detect channels in the cement behind the casing,
or to detect damage to cement from high-pressure injection of chemical
reaction. The cement-bond log is a continuous measurement of the am-
plitude of elastic waves after they have traveled through a short length
of pipe,  cement, and perhaps formation (Figure 46).  The amplitude of
the elastic wave is maximum in uncemented casing and will generally be
lower as the degree of bonding and integrity of the cement improves.
*Texas Railroad Commission rules.
                                  81

-------
   SURVEILLANCE OF OPERATING WELLS
3540
5550
SMO
                                     Figure 45.  Borehole televiewer log showing
                                                vertical fractures in the borehole
                                                wall of a well in Oklahoma
                                                (Zemaneketal., 1970).
                                        82

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                                         PERIODIC INSPECTION AND TESTING
                 TRANS
                  REC.
                                       CASING
                                        ONDED CEMENT
                                         /SHEATH/
                                       SONIC PULSE
                                       WAVE  FRONT
                               '::"••;!  ^"FORMATION"
                               *  • * * • /   _— ^_/"""—""
                       BORE
                       HOLE
                       LIQUID
           Figure 46. Schematic diagram of a cement bond logging tool
                    in a borehole (Grosmangin et al., 1960).

 Thus, the relative amplitudes of the waves in different portions of a well
 can be interpreted to indicate the condition of the cement and degree of
 bonding.  Complications that occur in the interpretation of cement-bond
 logs are discussed be Fertl et al. (1974).  Figure 47 shows portions of a
 cement-bond log from an acid wastewater injection well.  It appears that
 the casing in the vicinity of 1900 to 2000 feet is not bonded.  The interval
 from 2700 to 2800 feet, near the base of the casing, shows progressively
 better bonding between the casing and cement.

   Some other possible inspection methods are radioactive tracer injec-
 tivity profiles, flow-meter injectivity profiles,  and temperature profiles.
 The objective of these methods is to determine where injected fluid is
 going.  Radioactive tracer injectivity profiles accomplish this through
 injection of a radioactive tracer and logging of the borehole with a gamma
 ray detector.  The detector measures concentrations of tracer, which in-
 dicate paths of tracer flow.   Flow-meter injectivity profiles are similar,
 except that flow paths of injected fluid are indicated by a flow meter rather
 than by an injected tracer.  Temperature profiles may indicate anomalies
at points where injected fluids enter the receiving formation or where  they
 escape through casing or tubing leaks.  Such anomalies would obviously
be most likely to be detectable in wells where significant temperature  con-
trasts  exist between injected fluids and the aquifers.
                                  83

-------
SURVEILLANCE OF OPERATING WELLS
     1900
      2000
         =====3==5£3=:5335555=
         0-10 — 20— 50MOO
 2700
 2800
       PERCENT UNBONDED
          PIPE SIGNAL
Figure 47. Portions of a cement-bond
          log from an acid wastewater
          Injection well.
                                   84

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                                                     MONITORING WELLS
   Repetitive running of resistivity or radioactive logs may also be used
 to locate the zones that are accepting injected wastewater.  Resistivity
 logs are limited to the uncased portion of a well, but radioactive logs
 have been used to locate a freshwater-saline water interface behind casing
 (Keys  and MacCary,  1973).


 MONITORING WELLS
   The subject of monitoring wells has been a controversial one in regula-
 tion of wastewater injection.  Such wells are routinely used in shallow
 groundwater studies but are less frequently used in conjunction with waste-
 water  injection, for reason's that will be examined.

   At least three hydrogeologically different types of monitor wells can
 be and have been constructed,  each with different objectives as shown
 below:
              Well Type
         1.  Constructed in receiving
            aquifer — nondischarging
         2.  Constructed in or just
            above confining unit
            —nondischarging
         3,  Constructed in a fresh-
            water aquifer above
            receiving aquifer
     Objective
A.  Obtain geologic data
B.  Monitor pressure in
    receiving aquifer
C.  Determine  rate and
    direction of wastewater
    movement
D.  Detect geochemical
    changes in  injected
    wastewater
E.  Detect shifts in
    f r e s hwate r - s aline
    water interfaces

A.  Obtain geologic data
B.  Detect leakage through
    confining unit
A.  Obtain geologic data
B.  Detect evidence of fresh-
    water contamination
   Monitor wells constructed in the receiving aquifer are normally non-
discharging because a discharging well would defeat moat of the purposes
of this type of monitor well.  Also, the produced brines would have to be
disposed of.  Although it is not normally necessary to monitor pressure
in the receiving aquifer except at the injection well,  special monitor wells
may be desired where pressure at a distance from the injection well is of
concern because of the presence of known or suspected faults or aban-
doned wells that may be inadequately plugged.  The pressure response in
                                   85

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SURVEILLANCE OF OPERATING WELLS
a monitor well at such locations would indicate the extent of danger of
flow through such breaches in the confining beds and possibly also indi-
cate whether leakage was occurring.

   Constructing a monitor well or wells in the receiving aquifer is the
only direct means of verifying the rate and direction of wastewater move-
ment.  More than one well will frequently be necessary to meet this ob-
jective,  because monitor wells of this type only sample wastewater plumes
that pass directly through the well bore; and nonuniformity in aquifer por-
osity and permeability can cause the wastewater to arrive very rapidly
or perhaps not at all at a particular well.  A single well might be satis-
factory where aquifer and fluid properties are such that it is judged  most
likely that wastewater movement will be radial and reasonably uniform
ox where the objective is to detect wastewater arrival at a particular
point of interest.  These same comments apply to wells intended to de-
tect geochemical changes in injected wastewater.  A difference is  that a
well for  monitoring geo chemical changes would be placed near enough to
the injection well so that the wastewater front  will arrive within a  rela-
tively short time, whereas, a well for detecting wastewater arrival  at a
point of concern might be beyond the expected  ultimate travel distance of
the wastewater.

   A well intended  to detect a shift in a freshwater-saline water interface
should be located either  within that interface or in the freshwater portion
of the aquifer just beyond the interface.  Because movement of this inter-
face will be in response  to increased aquifer fluid pressure, rather  than
to actual displacement by the wastewater front, detection of its movement
should be possible  with a small number of observation wells, perhaps
even a single properly located one.  It is possible to estimate rates  of
movement for a particular case and to determine if a monitor well is
likely to be  able to  detect such a shift. Monitoring would be for confirm-
ation of the  calculations  and to allow for revisions in regulation if  unex-
pected results  occur.

   Negative factors should be considered in any case where deep monitor
wells are contemplated:   monitor wells in the  receiving aquifer may be
of limited usefulness, and they provide an additional means by which in-
jected wastewater could  escape from the receiving aquifer.   In a number
of cases, multiple  injection wells have been constructed at a site,  one or
more of which may be standby injection wells.  Standby wells can be used
for monitoring of aquifer pressure,  and for sampling of aquifer water.
However, if they have been operated or even extensively tested, their use
for monitoring may be impaired.

   Some examples  of the use of observation wells in  the receiving  aquifer
are given by Goolsby (1971 and 1972), Kaufman et al. (1973), Leenheer and
Malcom (1973), Peek and Heath (1973), and Hanby and Kidd (1973).
                                  86

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                                                  MONITORING WELLS
    For detection of leakage, the principal of using nondischarging monitor
 wells completed in the confining beds or in a confined aquifer immediately
 above the confining beds has been widely discussed but has been little used.
 This type of well has the potential for acting as a very sensitive indicator
 of leakage by allowing measurement of small changes in pressure (or water
 level) that accompany leakage. A well of this type is best suited for use
 where the confining unit is relatively thin and well defined and where the
 engineering properties of the two aquifers are within a range  such that
 pressure response in the monitored aquifer will be rapid if leakage occurs.
 Use of the concepts outlined by Witherspoon and Neuman (1972) will allow
 evaluation of the possibilities of success of this monitoring method in a
 specific situation.  In many actual cases, confining beds are several hun-
 dred to several thousand feet thick and do not contain aquifers suitable for
 such monitoring.   In other cases, the physical circumstances are amenable
 to such monitoring but several thousands of feet of interbedded aquitards
 and saline water aquifers  are present; in these cases, slow vertical leak-
 age across the aquitard immediately over the injection interval is not sig-
 nificant because it can be  predicted that there will be no  measurable influ-
 ence at the stratigraphic level where freshwater or other resources occur.

   Two good examples of the usefulness of monitoring an aquifer immedi-
 ately above the  confining beds  are provided by Kaufman et al. (1973) and
 Leenheer and Malcolm (1973).  In the case described by Kaufman et al.,
 wastewater leakage from the lower Floridan aquifer through 150 feet  of
 confining beds into the upper Floridan aquifer was detected by geochemi-
 cal analysis of water from a monitor well constructed in the upper Flori-
 dan aquifer. No pressure effects were noticed in this instance.   Leenheer
 and Malcolm summarized a case history in which leakage through the con-
 fining beds was  detected first by pressure increase in an overlying aquifer,
 and  later confirmed by chemical analysis which showed wastewater con-
 tamination of water in the aquifer.

   The type of monitor  well most commonly in use is that which is com-
 pleted in a freshwater aquifer above the injection horizon for detecting
 freshwater contamination.  In a number of locations,  this type of monitor-
ing is provided by wells that are a part of the plant's water supply system.
 In other cases,  the wells have  been constructed particularly for monitor-
 ing and are not used for water  supply.  Wells for detection of freshwater
 contamination should be discharging wells because they then sample an
 area of aquifer within their cone of depression.  As previously mentioned,
 nondis charging wells are of limited  value for detection of contamination
 because they sample only that water that passes through the well bore.
 Wells for monitoring freshwater contamination should be located close to
 the anticipated sources of  contamination, which are:
                                  87

-------
 SURVEILLANCE OF OPERATING WELLS


         • The injection well itself

         • Other nearby deep wells, active or abandoned
         * Nearby faults or fracture zones.

   No example is known to the writer where monitor wells of this type
 have detected wastewater contamination of a water supply aquifer.

   In the preceding discussion, it has been implied that separate wells
 would need to be constructed for surveillance of aquifers and aquicludes
 at different depths.  This is not necessarily the  case.  Talbot (1972)
 shows how the injection well itself can be adapted for monitoring of over-
 lying aquifers, and also how monitor wells may  be constructed for sur-
 veillance of more  than one aquifer.  Wilson et al. (1973) describe a case
 where the injection well was modified as shown in Figure  48 for monitor-
 ing of two aquifers overlying the injection  zone.

   Since the objectives for each of the types of monitoring wells discussed
 are worthwhile ones, why are monitor wells not more widely used?  The
 answer to this question is that the potential benefits are often judged to be
 small in comparison with the costs and negative aspects.  Therefore, such
 wells may not be voluntarily constructed by the operating  companies nor
 required by the regulatory agencies. In particular, monitor wells con-
 structed in the receiving aquifer are often difficult to justify because
 such wells are the most expensive form of surveillance and may yield
 very little  information that is important for regulation.  It can reasonably
 be concluded that monitor wells should not be arbitrarily required,  but
 should be used where the local circumstances justify them.

 OTHER MONITORING  METHODS

   A method of monitoring not so far mentioned is the sampling of springs,
 streams, or lakes that could be affectedly injection.  There are few in-
 stances where such monitoring would be applicable; but, for example
where springs originate along a fault within the area of pressure influence
of the injection well  an increase in discharge rate or change in water qual-
ity could be an indication of leakage of formation water along the fault in
 response to the increased pressure from injection.  Also, springs and
gaining streams act  similarly to discharging wells in  that  they provide a
composite  sample  of groundwater over their area of influence; thus,  they
might reveal leakage from unknown fracture zones or abandoned wells
that  connect a shallow groundwater aquifer with the injection interval.  In
a similar way, lakes may be collecting points for groundwater seepage or
streams and may reflect quality changes in shallow groundwater aquifers.

-------
              u
     UJ
      CO
           1000
      <  2000
      I
      UJ
           3000
      Ul
      UJ
      u.
      a.
      ui
      o
           4000
           5000
"W».PM
. Oiigocene
—
Eocene
-
Poleoceno
Lot*
Cretaceous
Y/S<

U
"C 3
O V
C»

H
0
(A
< Anhydrite- >
* dolomite y
^ confining beds*

•- 8
'o C
• 8
'iT
Tempo -Hawthorn- surf iciol
Suwonnee Limestone .
Ocolo
Avon
Loke
Group
Pork Limtston*
City Limtstont
Oldsmor LiiMtton* •
•
o
w
'jk
»
2
e
U
Upoor
Middle
Lower
Lowton Lim»ston«
ond b«d» of
Toylor og* (?)

                                                                                   30" Cosing


                                                                                   24" Casing
Cement  grout


Shollow  monitor
    well
                                                                                       Cosing
Detp  monitor
    well
iff Cosing
  o
                                                                                    Packer
Fiberglass
injection

tubing
 6^- Open hole
Figure 48.  Geologic column and construction of a wastewater injection well at Mulberry,  Florida, where two

           aquifers above the injection zone are monitored through the injection well (Wilson et a I., 1973).
                                m
                                70
                                O
                                z
                            z
                            o
                                                                                                                   o
                                                                                                                   o
                                                                                                                   CO

-------
SURVEILLANCE OF OPERATING WELLS
    Surface geophysical methods offer some limited possibilities for
monitoring of wastewater injection.  Barr (1973) discussed the feasibility
of monitoring the distribution of injected wastewater with seismic reflec-
tion.  Monitoring by seismic reflection depends on the existence of a suf-
ficient density contrast between injected and interstitial water,  and no
field trials of monitoring by seismic reflection have been reported.  Elec-
trical resistivity surveying could be useful for monitoring the movement
of freshwater-saline water interfaces or for detecting saline water pollu-
tion of freshwater aquifers (Swartz, 1937; Warner,  1969).

   Monitoring for earthquake occurrence is accomplished by use of a net-
work of seismometers placed in the vicinity of the injection well and in
the vicinity of nearby faults along which  seismic events might be triggered.
Examples  of this form of monitoring are described by Raleigh (1972) and
by Hanby and Kidd (1973).  In a case where  earthquake stimulation is con-
sidered a possibility, seismic monitoring should begin before the well is
operated to obtain background data.
                                   90

-------
                             SECTION V11I
                             REFERENCES
Barr, F. J.,  Jr.,  "Feasibility Study of a Seismic Reflection Monitoring
        System for Underground Waste-Material Injection Sites, " in
        Underground Waste Management and Artificial Recharge,
        Jules Braunstein, ed, p 207-218,  1973.
Bear, Jacob, Dynamics of Fluids in Porous Media, Elsevier Publishing
        Co., New York,  764 pages, 1972.
Bear, J., and M.  Jacobs, Th.e Movement of Injected Water Bodies in
        Confined Aquifers, Underground Water Storage Study Report
        No.  13, Technion, Haifa, Israel,  1964.
Berry, F.A.F., "High Fluid Potentials in California Coast Ranges and
        their Tectonic Significance, " Bull. Am. Assoc.  Petroleum
        Geologists, Vol.57, No. 7,  p  1219-1249,  1973.
Black, Crow, and  Eidsness, Inc., Engineering Report on Modification to
        Deep-Well Disposal System; Effect of Monitoring  Wells and Future
        Monitoring Requirements for Sugar Cane Growers Cooperative of
        Florida, Belle Glade, Palm Beach County. Florida, Engr. Rept.
        Proj. No.  387-71-01, 40 pages, 1972.
Bond, D. C., Hydrodynamics in  Deep Aquifers of the Illinois Basin, Illinois
        State Geological Survey Circular 470,  72 pages, 1972.

Bond, D. C., "Deduction of Flow  Patterns in Variable-Density Aquifers
        from Pressure and Water-Level Observations, " in Underground
        Waste Management and Artificial Recharge, Jules Braunstein,
        ed, Am. Assoc.  Petroleum Geologists, Tulsa, Oklahoma,
        p 357-378, 1973.
Bredehoeft,  J. D., and G. F. Pinder, "Application of Transport Equations
        to Groundwater Systems," in Underground Waste Management and
        Environmental Implications, T.D.  Cook,  ed, Am. Assoc. Petro-
        leum Geologists Memoir 18, p 191-199, 1972.
Brown, D. L., andW.D. Silvey, "Underground Storage and Retrieval
        of Fresh Water from a Brackish-Water Aquifer, "  in Underground
        Waste Management and Artificial Recharge, Jules Braunstein,
        ed, Am. ASSOC.  of Petroleum Geologists, Tulsa,  Oklahoma,
        p 379-419, 1973.


                                  91

-------
 REFERENCES
 Buschbach, T.C.,  Cambrian and Ordovician Strata of Northeastern
         Illinois, Illinois Geol. Survey Report of Investigations 218,
         90 pages,  1964.

 Clifford, M. J., "Hydrodynamics of the Mount Simon Sandstone, Ohio
         and Adjoining Areas," in Underground Waste Management and
         Artificial Recharge, Jules Braunstein,  ed,  Am. Assoc.  of
         Petroleum Geologists,  Tulsa, Oklahoma, p 349-356, 1973.

 Cook, T. D.,  ed, Underground Waste Management and Environmental
         Implications. Am. Assoc. of Petroleum Geologists Memoir 18,
         412 pages,  1972.

 Davis, S.H.,  and R. J.M.  De Weist, Hydrogeology.  Wiley and Sons,  Inc.,
         New  York, New York, 463 pages, 1966.

 Dickinson, George, "Geological Aspects of Abnormal Reservoir Pres-
         sures in the  Gulf Coast Louisiana," Am. Assoc. Petroleum
         Geologists Bull.. Vol.  37, No.  2, p 410-432, 1953.

 Eisenberg, D., and W. Kauzmann, The Structure and Properties of
         Water. Oxford University Press, New York, New York,  296
         pages, 1969.

 Ferris,  J. G., et al., Theory of Aquifer Tests.  U.S. Geological Survey
         Water Supply Paper 1536-E,  174 pages, 1962.

 Fertl, W.H.,  et al.,  "A Look at Cement Bond Logs, "  Jour,  of Petro-
         leum Technology, Vol 26, p 607-617, June 1974.

 Gatlin, Carl,  Petroleum Engineering Drilling and Well Completions.
         Prentice-Hall, Inc., Englewood Cliffs,  N. J., I960.

 Gelhar,  L. W., and others,  Density Induced Mixing in Confined Aquifers.
         U.S.  Environmental Protection Agency  Water Pollution Control
         Research Series Publication 16060 ELJ 03/72,  1972.

 Goolsby, D. A., "Hydrogeo chemical Effects of Injecting  Wastes into a
         Limestone Aquifer near Pensacola, Florida, " Ground Water
         Vol 9, No. 1, p 13-19,  1971.                	;—!	'

 Goolsby, D. A., "Geochemical Effects and Movement of Injected Indus-
         trial  Waste in a Limestone Aquifer, " in Underground Waste
         Management  and Environmental Implications. Am. Assoc. of
         Petroleum Geologists Memoir 18, Tulsa, Oklahoma, p 355-367,
         1 7/2.

Gould, H.R.,  History of the AAPG Geothermal Survey of North America,
         unpublished paper presented at the 1974 Am. Assoc.  of Petroleum
         Geologists Annual Meeting, San Antonio, Texas, 1974.
                                 92

-------
                                                        REFERENCES
 Grosmangin, M., et al., "A Sonic Method for Analyzing the Quality of
         Cementation of Borehole Casings, " Jour, of Petroleum Tech-
         nology, p 165-171, February 1961.

 Hall, C.W., and R.K.  Ballentine, "U.S.  Environmental Protection Agency
         Policy on Subsurface Emplacement of Fluids by Well Injection, "
         in Underground Waste Management and Artificial Recharge,  Jules
         Braunstein, ed, Am. Assoc.  of Petroleum Geologists,  Tulsa,
         Oklahoma,  p 783-793,  1973.
 Hanby, K. P. ,  and R.E. Kidd,  "Subsurface Disposal of Liquid Industrial
         Wastes in Alabama—A  Current Status Report, " in Underground
         Waste Management and Artificial Recharge,  Jules Braunstein,
         ed, Am. Assoc.  Petroleum Geologists,  Tulsa, Oklahoma,
         p 72-90, 1973.
 Hanshaw, B.B.,  "Natural Membrane Phenomena and Subsurface Waste
         Emplacement," in Underground Waste Management and Environ-
         mental Implications, T. D., Cook,  ed, Am. Assoc. of Petroleum
         Geologists Memoir 18, Tulsa, Oklahoma, p 308-315, 1972.

 Haun,  J.D., and L. W.  Le Roy, eds,  Subsurface Geology in Petroleum
         Exploration, Colorado  School of Mines,  Golden, Colorado,  1958.

 Hubbert,  M.K., and D.G.  Willis, "Mechanics of Hydraulic  Fracturing, "
         in Underground Waste Management and Environmental Implica-
         tions, T.D. Cook, ed,  Am.  Assoc. of Petroleum  Geologists
         Memoir 18, Tulsa, Oklahoma, 411 pages,  1972.

 Illinois Water Survey,  Feasibility Study of Desalting Brackish Water
         from the Mt. Simon Aquifer in Northeastern Illinois,  Urbana,
         Illinois, 120 pages,  1973.

 Jans sens, A.,  Stratigraphy of the Cambrian and Lower Ordovician Rocks
         in Ohio,  Ohio Division of Geological Survey Bulletin 64,  197 pages,
         1973.
 Jennings, H.Y., and A. Timur, "Significant Contributions in Formation
         Evaluation and Well Testing, " Jour. Petroleum Technology,
         Vol 25, p 1432-1446, December 1973.

Katz, D. L., andD.L. Coats, Underground Storage of Fluids, Ulrich's
         Books, Inc., Ann Arbor, Michigan, 575 pages, 1968,

Kaufman, et al. , "Injection of Acidic Industrial Waste in a Saline Car-
         bonate Aquifer," in Underground Waste Management and Arti-
         ficial Recharge, Jules Braunstein,  ed, Am. Assoc. Petroleum
         Geologists,  Tulsa, Oklahoma, p 526-551, 1973.

Kehle, R. O.,  "The Determination of Tectonic Stresses through Analysis
         of Hydraulic Well Fracturing," Jour. Geophys. Research, Vol. 69
         No. 2, p 259-273, 1964.
                                 93

-------
REFERENCES
Keys,  W.S. , and R.F. Brown, "Role of Borehole Geophysics in Under-
         ground Waste Storage and Artificial Recharge, " in U nderground__
         Waste Management and Artificial Recharge,  Jules Braunstein,
         ed, Am. Assoc.  of Petroleum Geologists,  Tulsa, Oklahoma,
         p 147-191,  1973.
Keys,  W.S., andL.M. MacCary, Location and Characteristics of the
         Interface between Brine and Fresh Water from Geophysical
         Logs of Boreholes in the Upper Brasos River Basin, Texas,
         U.S. Geological Survey Prof. Paper 809-B,  23 pages,  1973.
Kirkpatrick, C. V.,  "Formation Testing, "  The Petroleum Engineer,
         p B-139,  1954.

Kruseman, G. P., and N. A. DeRidder, Analysis  and Evaluation of Pump-
         ing Test Data, International Institute for Land Reclamation and
         Improvement,  Bulletin 11,  Wageningen,  The Netherlands, 200
         pages, 1970.

Leenheer, J. A., and R. L. Malcolm, "Case History of Subsurface Waste
         Injection of an Industrial Organic Waste,"  in Underground Waste
         Management and Artificial Recharge,  Jules Braunstein, ed, Am.
         Assoc. Petroleum Geologists, Tulsa, Oklahoma, p  565-584,  1973.
Lohman,  S.H., Ground-Water Hydraulics,  U.S.  Geol. Survey Prof.
         Paper 708, 70 pages, 1972.

Lynch, E. J., Formation Evaluation, Harper and Row, New York, New
         York, 422 pages, 1962.

Matthews, C.S., and D. G. Russell, Pressure Buildup and Flow Tests in
         Wells, Am. Inst. of Mining,  Met., and Petr. Engrs., Soc. of
         Petroleum Engrs., Monograph Vol 1, 1967.

Moore, C.A.,  ed, Second Symposium on Subsurface Geological Techniques,
         University of Oklahoma  Extension Division, Norman, Oklahoma,
         1951.

Murphy, W. C., The Interpretation and Calculation of Formation Charac-
         teristics from Formation Test Data, Halliburton Services, Duncan,
         Oklahoma,  undated.

Ohio River Valley Water Sanitation Commission, Underground Injection of
         Wastewater in the Ohio Valley Region, Cincinnati, Ohio, 63 pages,
         1973.

Pe^k,  H.M. ,  and R. C. Heath, "Feasibility Study of Liquid-Waste Injection
         into Aquifers  Containing Salt Water, Wilmington, North Carolina,"
         in Underground Waste Management and Artificial Recharge, Jules
         Braunstein, ed, Am. Assoc.  Petroleum Geologists, Tulsa, Okla-
         homa,  p 851-878, 1973.
                                 94

-------
                                                         REFERENCES
 Pirson,  S. J., Handbook of Well Log Analysis, Prentice-Hall, Inc. ,
         Englewood Cliffs, New Jersey, 326 pages,  1963.
 Raleigh, C. B. , "Earthquakes and Fluid Injection, " in Underground Waste
         Management and Environmental Implications, T.D.  Cook, ed,
         Am. Assoc. of Petroleum Geologists Memoir 18, p 273-279,
         1972.
 Robertson,  J.B., and J. T Barraclough, "Radioactive- and Chemical-
         Waste Transport in Groundwater at National Reactor Testing
         Station, Idaho:  20-year Case History and Digital Model, " in
         Underground Waste Management and Artificial Recharge, Jules
         Braunstein, ed, Am. Assoc.  Petroleum Geologists, Tulsa,
         Oklahoma, p 291-322, 1973.
 Sbar, M.L., and M.L. Sykes, "Contemporary Compressive Stress and
         Seismicity in  Eastern North America: An Example of Intra-Plate
         Tectonics." Geol. Soc. of Am. Bull., Vol 84, No.  6, p 1861-1882,
         1973.
 Schlumberger,  Limited, Schlumberger Engineered Production Services,
         Schlumberger, Limited, Houston,  Texas,  1970.

 Schlumberger,  Limited, Log Interpretation Volume I—Principles, Schlum-
         berger, Limited,  New York,  New York, 1972.
 Schlumberger,  Limited, Log Interpretation Charts, Schlumberger, Limited,
         U.S.A.,  1972a.
Swartz, J.H., "Resistivity Studies  of some  Saltwater Boundaries in the
        Hawaiian Islands, "  Trans. Am.  Geophysical Union, Vol 18,
        p 387-393, 1937.
Talbot,  J. S., "Requirements for Monitoring of Industrial Deep Well Dis-
        posal Systems," in Underground Waste Management and Environ-
        mental Implications, T.D. Cook, ed, Am.  Assoc. Petroleum
        Geologists Memoir 18, p 85-92, 1972.
Warner,  D.L., Deep-Well Injection of Liquid Waste,  U.S.  Dept. of Health,
        Education, and Welfare, Public Health Service Publication No.
        99-WP-21, 55 pages, 1965.
Warner,  D.L., "Subsurface Disposal of Liquid Industrial Wastes by Deep-
        Well Injection," in Subsurface Disposal in Geologic Basins—A
        Study of Reservoir Strata,  J. E. Galley, ed, Am. Assoc. Petro-
        leum Geologists Memoir 10, p 11-20, 1968.
Warner,  D.L., "Preliminary Field Studies Using Earth Resistivity
        Measurements for Delineating Zones of Contaminated Ground
        Water. " Ground Water, Vol.  7, No. 1, p. 9-16, 1969.
                                 95

-------
 REFERENCES
Warner, D.L. , and D.H. Orcutt,  "Industrial Wastewater-Injection Wells
        in the United States—Status of Use and Regulation,  1973, " in
        Underground Waste Management and Artificial Recharge, Jules
        Braunstein, ed, Am. Assoc. of Petroleum Geologists, Tulsa,
        Oklahoma, p 687-697, 1973.
Wilson, W.E. , et al, "Hydrologic Evaluation of Industrial-Waste Injection
         at Mulberry, Florida," in Underground Waste Management and
         Artificial Recharge,  Jules Braunstein, ed,  Am. Assoc. Petroleum
         Geologists, Tulsa, Oklahoma, p 552-564, 1973.

Witherspoon,  et al, Interpretation of Aquifer Gas Storage Conditions from
         Water Pumping Tests,  Am. Gas Assoc. , Inc. , New York, New
         York, 273 pages, 1967.

Witherspoon,  P. A., andS.P. Neuman,  "Hydrodynamics of Fluid Injection, "
         in Underground Waste Management and Environmental Implications,
         T.D. Cook, ed,  Am. Assoc.  Petroleum Geologists Memoir  18,
         Tulsa, Oklahoma,  1972.

Zeznanek, Joe, et al, "Formation Evaluation by Inspection with the Bore-
         hole  Televiewer, " Geophysics,  Vol 35, No.  2, p 254-269, 1970.
                                  96

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                                          APPENDIX

             EPA POSITION ON SUBSURFACE EMPLACEMENT OF FLUIDS
    The material in this appendix is reproduced from the Federal  Register
of April  9,  1972,  pp 12922-12933.  (See also Hall and Ballentine,  1973)
INTRODUCTORY COMMENTS

  The Environmental Protection Agency.
 in concert with the objectives of the Fed*
 eral Water Pollution Control Act, as
 amended (33 U.S.C. 1251 et aeq.; 86 Stat.
 816 et seq.; Pub. L. 92-500)  "... to
 restore and maintain the chemical, phy-
 sical, and biological integrity of the Na-
 tion's water"  has established an EPA
 policy  on  Subsurface Emplacement of
 Fluids by Well Injection" which was is-
 sued internally as Administrator's Deci-
 sion Statement No. 5. The purpose of the
 policy is to establish the Agency's con-
 cern with this technique for use In fluid
 storage and disposal and its position of
 considering such fluid emplacement only
 where it is demonstrated to be the most
 environmentally  acceptable  available
 method of handling fluid storage or dis-
 posal. Publication of the Policy as In-
 formation establishes the Agency's posi-
 tion and provides guidance to other Fed-
 eral Agencies,  the States, and other In-
 terested parties.
  Accompanying  the  policy statement
 are "Recommended Data Requirements
 for Environmental Evaluation of Sub-
 surface Emplacement of Fluids by Well
 injection  wen system:  and to  insure
 ments is to provide guidance for potential
 injectors and  regulatory agencies con-
 cerning the kinds of information re-
 quired  to  evaluate  the  prospective
 injections  well system;  and  to  insure
protection  of  the  environment. The
Recommended Data  Requirements  re-
quire sufficient Information to evaluate
complex  Injection operations for haz-
ardous materials, but may be modified
In scope by  a regulatory agency  for
other types of Injection operations.
  The EPA recognizes that for certain
industries and in certain locations the
disposal of wastes and  the storage of
fluids hi the subsurface by use of  well
injection may be the most environmen-
tally acceptable practice  available. How-
ever, adherence  to the  policy requires
the potential injector to clearly demon-
strate acceptability by the provision of
 technical analyses and  data justifying
 the  proposal. Such  demonstration  re-
 quires  conventional  engineering  and
 other  analyses which indicate beyond
 a reasonable doubt the  efficacy of  the
 proposed  injection well  operation.
   Several issues within the policy should
 be highlighted and explained to  avoid
 confusion. One of the goals of the pol-
 icy is to protect the Integrity of  the
 subsurface environment. In the context
 of the policy statement, integrity means
 the prevention of unplanned fracturing
 or other physical impairment of the geo-
 logic  formations and-the  avoidance of
 undesirable changes in aquifers, mineral
 deposits or other resources. It is recog-
 nized that fluid emplacement by well
 injection  may cause  some  change  in
 the environment and, to  some extent,
 may preempt other uses.
  Emplacement is  intended  to include
 both disposal  and  storage. The differ-
 ence between the two terms is that stor-
 age implies the existence of  a plan  for
 recovery of the material within a rea-
 sonable time whereas disposal implies
 that  no recovery  of the material is
 planned at a  given site. Either opera-
 tion  would require  essentially the  same
 type of information prior to injection.
 However, the attitude of the appropriate
 regulatory agency toward evaluation of
 the proposals would be different for each
 type operation. The EPA policy recog-
 nizes the need for injection wells in cer-
 tain oil and mineral extraction and fluid
 storage operations but requires sufficient
 environmental safeguards  to  protect
 other uses of the subsurface, both dur-
 ing the actual Injection operation and
 after the Injection has  ceased.
  The policy considers waste disposal by
well injection to be a temporary means of
disposal hi the sense that it is approved
only  for the life of  an  issued, permit.'
Should more environmentally acceptable
disposal technology become available, a
change to such technology  would be  re-
quired. The term "temporary" is not in-
tended to Imply subsequent recovery of
                                       97

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APPENDIX
injected waste for processing by another
technology.
  Paragraph 5 of the policy and program
guidance provides that EPA will apply the
policy to the extent of its authorities in
conducting all EPA program activities.
The applicability of the policy to partici-
pation by the  several  States  In the
NPDES permit  program under  section
402 of the Federal Water Pollution Con-
trol Act as amended has been established
previously by { 124.80(d) of Part 124 en-
titled "State Program Elements Neces-
sary  for Participation In the National
Pollutant  Discharge  Elimination  Sys-
tem." 37 PR 28390  (December 22, 1972).
These guidelines provide that each EPA
Regional Administrator  must distribute
the policy to the Director of a State water
discharge permit Issuing agency, and
must utilize the policy In his own review
of any permits for disposal of pollutants
Into wells that are proposed to be issued
by States participating in the NPDES.

  Dated: April 2,1974.

                      JOHN OVARIES,
                 Acting Administrator.


ADMINISTRATOR'S DECISION STATEMENT
NO.   5 EPA  POLICY  ON  SUBSURFACE

EMPLACEMENT OP  FLUIDS  BY WELL

INJECTION
   This ADS records the EPA'* position on in-
 jection wells and subsurface emplacement of
 fluids by well injection. Mid supersedes the
 Federal Water Quality Administration's order
 COM 6040.10 of October 15. 1970.
   Goals. The EPA  Policy on Subsurface Em-
 placement of Fluids by Well  Injection Is
 designed to:
   (1) Protect the subsurface  from pollu-
 tion or other  environmental hazards attrib-
 utable to Improper Injection or Ill-sited In-
 jection wells.
   (2) Ensure that engineering and geological
 safeguards adequate to protect the integrity
 of the subsurface environment are adhered
 to In the  preliminary Investigation, design.
 construction,  operation,   monitoring  and
 abandonment phase* of Injection well proj-
 ects.
   (3) Encourage development of alternative
 means of disposal which afford greater en-
 vironmental protection.
   Principal finding* ant  policy  rationale.
 The available evidence concerning Injection
 wells and  subsurface emplacement of fluids
 Indicates that:
   (1) The emplacement of fluids by subsur-
 face Injection often  Is considered by govern-
 ment and private agencies as an attractive
 mechanism for final disposal or storage owing
 to: (a) the diminishing capabilities of sur-
 face waters to receive effluents  without vio-
 lation of  quality standards, and  (b)  the
 apparent tower costs of this method of dis-
 posal or storage over conventional  and  ad-
 vanced   waste   management  techniques.
 Subsurface storage capacity is a natural re-
 source of considerable  value and like any
 other natural resource its use must be con-
 served for maximal benefits to all people.
   (9) Improper Injection  of municipal  or
 Industrial wastes or  Injection of other fluids
   for storage or disposal to the subsurface en-
   vironment could result  In serious pollution
   of water supplies or other environmental
   hazards.
     (3)  The effects of subsurface Injection and
   the fate of Injected materials are uncertain
   with  today's knowledge  and could result In
   serious pollution or  environmental damage
   requiring complex and costly solutions on a
   long-term basis.
     Policy and program guidance. To ensure
   accomplishment of the subsurface protection
   goals established above It Is the policy of the
   Environmental  Protection Agency that:
     (1)  The EPA will oppose emplacement of
   materials by subsurface injection without
   strict  controls  and  a clear demonstration
   that  such emplacement will not Interfere
   with present or potential use of the subsur-
   face) environment, contaminate ground water
   resources or otherwise damage the environ-
   ment.
     (3)  All proposals for subsurface Injection
   should be critically evaluated to determine
   that:
     (a)  All reasonable alternative measures
   have been explored and found less satisfac-
   tory In terms of environmental protection;
     (b)  Adequate prelnjectlon tests have been
   made  for predicting  the fate of materials
   Injected;
     (c)  There Is conclusive technical evidence
   to demonstrate that such injection will not
   Interfere with  present or potential use of
   water resources nor result In other environ-
   mental hazards:
     (d)  The subsurface injection system has
   been designed  and constructed to  provide
   maximal environmental protection;
     (e)  Provisions have been made for moni-
   toring both the injection operation and the
   resulting effects on the environment;  .
     
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                                                                                                  APPENDIX
well injection has been prepared to establUb
the Agenty's position on the u*e of this dls-
poeal and storage technique. To aid In Im-
plementation  of  the policy • recommended
data base for environmental evaluation has
been developed.
  The following parameters describe the In-
formation which should be provided by the
Injector and are designed to provide regula-
tory agencies sufficient Information to evalu-
ate the environmental acceptability of any
proposed well Injection. A potential Injector
should Initially contact the regulatory au-
thority to determine the preliminary Investi-
gative and data requirements for a particular
Injection well as these may vary for different
kinds of injection operations. The appropriate
regulatory authority will specify the exact
data requirements on a case by ease basis.
  (a) An accurate plat showing location and
surface elevation of proposed Injection welt
site, surface features, property boundaries.
and surface and mineral ownership  at  an
approved scale.
  (b) Maps indicating location of water wells
and all other  wells, mines or artificial pene-
trations, Including but not limited to oil and
gas wells and exploratory or test wells, shov-
ing depths, elevations and the deepest forma-
tion penetrated within twice the calculated
zone  of  influence of  the proposed project.
Plugging and abandonment records for all oil
and gas tests, and water wells should accom-
pany the map.
  (c)  Maps indicating vertlcaj and lateral
limits of potable water supplies which would
include both short- and long-term variations
In  surface  water supplies and  subsurface
aquifers containing  water with  less than
10000 mg '1 total dissolved solids. Available
amounts and present and potential uses of
these waters, as well as projections of  public
water supply  requirements must be consid-
ered.
  (d)  Descriptions of mineral resources pres-
ent  or believed  to be present  In area of
project and the effect  of this  project  on
present or potential mineral resources to the
area*
  (e) Maps and cross sections at approved
scales illustrating detailed geologic structure
and a stratigrapble section (Including for-
mations, llthology,  and physical characteris-
tics)  for the local area, and generalized maps
and cross sections Illustrating the regional
geologic setting of the project.
  (f) Description of chemical, physical, and
biological properties and characteristics of
the fluids to be injected.
'  (B)  Potentiometrtc  maps  at  approved
scales and  isopleth  Intervals of  the pro-
Dosed Injection horiBon and of those aquifers
SSmeWtely above and «~ «J»jWf"«
borleon. with copies  of^ all  *aa**"*?
charts, extrapolations, and data used In com-
  ll(hf M&t of the location and nature
 of  present or potentially useable minerals
 from the cone of Influence.
   
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                                 TECHNICAL REPORT DATA
                          (Please read Instructions on the reverse before completing}
 REPORT NO.
   EPA-680/4-75-008
                            2.
                                                         3. RECIPIENT'S ACCESS!
 TITLE AND SUBTITLE

     MONITORING  DISPOSAL-WELL SYSTEMS
            6. REPORT DATE
               July 1975
            6. PERFORMING ORGANIZATION CODE
 AUTHOR(S)

 Prof.  Don L.  Warner (Consultant)
            8. PERFORMING ORGANIZATION REPORT
              GE74TMP-45
 PERFORMING ORGANIZATION NAME AND ADDRESS
 TEMPO, General Electric Center for Advanced Studies^
           Santa Barbara, California
             10. PROGRAM ELEMENT NO.
                 1H1326
              .CONTRACT/GRANT NO.

               EPA 68-01-0759
12. SPONSORING AGENCY NAME AND ADDRESS
  National Environmental Research Center
  Office of Research and Development
  U.S.  Environmental Protection Agency
  P.O.  Box 15QZ7.  Las Vgpa«. WV  «Q1 14
                                                         13. TYPE OF REPORT AND PERIOD COVERED
             14. SPONSORING AGENCY CODE

                NA
15. SUPPLEMENTARY NOTES
 Environmental Protection Agency Report No.  EPA-680/4-75-008
16. ABSTRACT
           The Environmental Protection Agency is required,  under P. L. 92-500,
           The Federal Water Pollution Control Act Amendments of 1972, to esta-
           blish a system for the surveillance of the quality of the nation's surface
           and ground waters.  Enactment of P. L. 93-523, the Safe Drinking Water
           Act, further requires that State programs  in order to be approved,  shall
           include monitoring programs to prevent underground injection which en-
           dangers drinking water sources.  This  report provides information con-
           cerning the data needed for monitoring the subsurface injection of waste-
           water through cased disposal wells,  and discusses the methods and tools
           available for obtaining the data.  The procedures  for using the data  for
           predicting the response of the receiving aquifer to injection are then out-
           lined.  Surveillance of operating disposal wells is reviewed.  Numerous
           examples are given throughout the text.
17.
                               KEY WORDS AND DOCUMENT ANALYSIS
a.
                 DESCRIPTORS
b.IDENTIFIERS/OPEN ENDED TERMS
c. cos*Tl Field/Group
  Monitoring, 'Underground Waste Disposal, '"Industrial Wastes
  *Disposal Wells, "Injection Wells, Groundwater Quality,
  Groundwater, *Wastewater, Aquifer Characteristics, Pollution
  Control, Aquifers, Aquifer Management, Groundwater
  Management, Groundwater Movement, Observation Wells,
  Liquid Wastes, Malenclaves
                           02F,  02K,  05B,
                           05G,  08A,  08E
18, DISTRIBUTION STATEMENT

      Available from NTIS
19. SECURITY CLASS (ThisReport)'
   UNCLASSIFIED
21. NO. OF PAGES
    109
20. SECURITY CLASS (Thispage)
   UNCLASSIFIED
22. PRICE
EPA Form 2220-1 (9-73)

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