\ I /
United States
Environmental Protection
Agency
Robert S. Kerr Environmental
Research Laboratory
Ada OK 74820
Research and Development
EPA-600/S2-84-121 Sept. 1984
£,V>
v>EFV\ Project Summary
Methods for Determining the
Mechanical Integrity of Class II
Injection Wells
David M. Nielsen and Linda Alter
The Underground Injection Control
(UIC) program regulations require
injection well operators to test the
mechanical integrity of injection wells on
a periodic basis. The testing is to ensure
that there is no significant leak in the
casing, tubing or packer, and that there
is no significant fluid movement through
vertical channels adjacent to the injec-
tion well.
There are a number of methods
available for mechanical integrity test-
ing. These include monitoring of annu-
lus pressure, pressure testing, tempera-
ture logging, noise logging, pipe analy-
sis surveys, electromagnetic thickness
surveys, caliper logging, borehole
television, borehole televiewer, flow-
meter surveys, radioactive tracer sur-
veys and cement and cement bond log-
ging. Only temperature logging, noise
logging and radioactive tracer surveys
can be utilized to provide relatively de-
finitive information regarding the pre-
sence or absence of fluid movement
behind casing; cement bond logs pro-
vide information from which fluid
movement may be inferred. With the ex-
ception of cement bond logging, all of
the testing methods can be used to lo-
cate leaks in casing.
The full report describes each of the
methods that can be used in mechanical
integrity testing, including the princi-
ples, equipment, procedures, interpre-
tation, cost, advantages and disadvan-
tages and examples of each technique.
Other methods which may also have
application in mechanical integrity test-
ing, but which require additional field
testing to establish their effectiveness,
are also described.
This Project Summary was developed
by EPA's Robert S. Kerr Environmental
Research Laboratory, Ada. OK. to
announce key findings of the research
project that is fully documented in a
separate report of the same title (see
Project Report ordering information at
back).
Introduction
Public Law 93-523, the Safe Drinking
Water Act, requires the U.S. Environ-
mental Protection Agency to develop
minimum requirements to assist in the
establishment of effective state programs
to protect underground sources of
drinking water from contamination
resulting from the subsurface emplace-
ment of fluids through well injection.
Inherent in a process for protecting
underground sources of drinking water is
the determination of the mechanical
integrity of the injection well. An injection
well is determined to have mechanical
integrity when it meets both of the
following criteria: 1) there is no signifi-
cant leak in the casing, tubing or packer;
and 2) there is no significant fluid
movement into an undergound source of
drinking water through vertical channels
adjacent to the injection well.
The full report is intended to provide a
concise description of methods or tech-
nologies which are currently being used
or which may have application in deter-
mining the mechanical integrity of an
injection well.
Procedure
In developing the full report, past,
present and potentially available methods
for determining the mechanical integrity
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of injection wells were researched
Government officials in oil and gas
producing states were surveyed regarding
regulations, requirements, methods and
procedures used to determine mechanical
integrity of injection wells. Efforts were
made to document the applicability of
many types of services provided by well
logging companies. Attempts were also
made to assess the applicability of many
types of equipment for determining the
mechanical integrity of injection wells
and to identify the availability of compa-
nies able lo perform mechanical integrity
services
Results
A review of the available literature
revealed that a significant amount of
information has been written about the
testing of wells of downhole problems
such as leaks in the casing or flow behind
the casing. However, most of the work
described in the literature has involved
the testing and inspection of producing oil
and gas wells rather than injection wells.
Fortunately, most of this technology is
also applicable to injection wells.
In general, two types of injection
wells are used in oil and gas production
operations 1) brine disposal wells in
which the fluid is injected into a receiving
formation for the purpose of retention;
and 2) enhanced recovery wells in which
the fluid is injected into a producing
formation for the purpose of increasing
the production of oil or gas.
Injection wells can be operated without
endangering ground water provided they
are properly constructed and maintained
in such a way as to ensure their
mechanical integrity. Saltwater injected
under pressure or by gravity into wells
may escape through leaks in the well
casing caused by a mechanical failure
within the well, or through migration of
brine forced up between the well's outer
casing and the wellbore because of a
faulty cementing job. Determination of
the mechanical integrity of an injection
well is extremely important, since it
provides a measure of the protection of
underground sources of drinking water
from contamination.
Conclusions
The Underground Injection Control
(UIC) program requ ires that the absence of
a significant leak in the casing, tubing or
packer be evaluated using either monitor-
ing or annulus pressure, pressure testing
with liquid or gas or, in specified instan-
ces, monitoring records that show no sig-
nificant change in the relationship be-
tween injection pressure and injection
flow rate. The absence of significant fluid
movement can be evaluated by using the
results of a temperature or noise log, or,
by presenting well records that demon-
strate the presence of adequate cement
to prevent migration.
There are a number of other methods
which are not currently approved for use
which may be used to determine the
mechanical integrity of injection wells.
Pipe analysis surveys, electromagnetic
thickness surveys, caliper logging, flow-
meter surveys, radioactive tracer surveys
and cement bond logs, which are avail-
able from professional well logging com-
panies, are capable of detecting leaks in
the casing, tubing or packer and/or fluid
movement behind casing. Borehole tele-
vision and borehole televiewer surveys,
which are performed by specialized con-
tractors, may also be used to detect leaks*
Table 1 provides a detailed listing of the
detection capabilities, well diameter con-
straints and pressure/temperature limi-
tations of each of these techniques as
well as the techniques approved for use
in the UIC program.
The advantages and disadvantages of
each method must be understood to
facilitate a rational decision regarding
which method or methods can be applied
in each individual situation. Few of the
methods which can be employed to test
the mechanical integrity of injection
wells can be used alone to provide
definitive information on both the pre-
sence and the location of leaks in the
casing, tubing, or packer, and fluid
movement behind the casing. In general,
it will take two or more testing techniques,
run either independently or in conjunc-
tion, to ensure that no significant leaks
exist in the casing and that no fluid
movement is occurring in the cement
sheath behind the casing. Table 2 provides
a detailed summary of the advantages
and disadvantages of all methods which
maybe used to determine the mechanical
integrity of injection wells.
Recommendations
There are many methods that may be
applicable for determining the mechanical
integrity of injection wells. Because of the
many variations in injection well com-
pletions, it is not possible to make
recommendations regarding mechanical
integrity testing methods that apply to all
such wells. Since each is unique, testing
procedures should be carefully selected
and tailored to the individual well. The
following list of criteria should be used to
help establish a systematic approach to
choosing the appropriate testing meth-
ods:
1) Determine the type of completion of
the well;
2) In wells completed with tubing and
packer, determine the type of packer
to evaluate the maximum amount of
pressure which can be applied to the
annulus between the tubing and
casing;
3) Determine the inside diameter of
the casing or tubing to assess tool
diameter limitations;
4) Determine the depth of the well to
evaluate the pressure/temperature
limitations;
5) Determine the wall thickness of
casing or tubing since selected
methods rely on the measurement
of thickness to determine the sound-
ness of the pipe;
6) Attempt to determine the interval(s)
of injection to facilitate the applica-
tion or interpretation of tests;
7) Evaluate the availability of profes-
sional companies to perform the
service, if applicable; and
Table 1 Summary of Applications of Methods Which May be Used to Determine the Mechanical Integrity of Class II Infection Wells
Detection Capability
Monitoring Annulus Pressure
Pressure Testing
Temperature Logging
{Gradient)
(Differential)
tFtadial Differential}
Noise Logging
Pipe Analysis Survey
Electromagnetic Thickness Survey
Mechanical Caliper Logging
Borehole Television
Borehole Televiewer
Flowmeter Surveys
Radioactive Tracer Surveys
Cement Bond Logging
Leaks in Casing
Tubing or Packer
X
X
X
X
X
X
X
X
X
X
X
X
X
Fluid Movement
Behind Casing
X
X
X
X
X
*
Well Diameter
Constraints
Minimum
N/A
N/A
1'/2"
1V,"
2'/i"
1'/i"
4V,"
4'/i"
2"
3"
2Vt"
2"
r/i"
2"
Maximum
N/A
N/A
8
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8) Evaluate the cost of the method with
respect to the type of results desired.
Further study is needed in the following
areas:
1) Gamma ray logging has traditionally
been used in injection wells for
purposes other than leak detection,
however further study into the
applicability for leak detection is
needed;
2) Helium leak testing has been used to
test for leaks in other applications but
has not been applied specifically to
injection wells. This method should
be laboratory and field tested to
determine its applicability to injec-
tion wells;
3) Volumetric scanning has been used
for fracture evaluation in open bore-
holes. Further evaluation for use in
cased hole applications is needed;
and
4) Continuous oxygen activation log-
ging has been field tested for ap-
plication in determining leaks in
injection wells but the results are
inconclusive. Further testing is
needed to assess the applicability of
this technique.
Monitoring Annulus
Pressure
Table 2. Summary of Advantages and Disadvantages of Methods That May Be Used to
Determine the Mechanical Integrity of Class II Injection Wells
Method Advantages Disadvantages
Provides "real time" measurement
Well does not have to be taken out of service
No specialized equipment needed
Very inexpensive
Provides either continuous or frequent, regular
measurement
Pressure Testing Most tests of short duration
Minimum of specialized equipment needed
Relatively inexpensive for most wells
Results straightforward and easy to intrepret
Staged tests provide information on leak location
Temperature Logging Can detect and locate both leaks in casing. Requires professional service, equipment and
tubing or packer and fluid movement in channels interpretation
behind casing
Gradient and differential logs available from most Requires removal of weft from service for extended
logging companies period (24 to 48 hours or more)
Use limited in large-diameter wells
Radial differential log available from only one logging
company
Injected fluid temperature and pressure changes
complicate interpretation
Provides no information on leak location
Limited to use in wells completed with tubing and
packer
Some disruption of service
Non staged tests provide no information on leak
location
Application of excessive pressures could damage
well
Noise Logging Can detect and locate both leaks in casing, tubing Requires professional service, equipment and
or packer and fluid movement behind casing interpretation
Possible to distinguish between single and dual May require removal of well from service for extended
phase flow period
Possible to estimate rate and volume of flow from Injection operations must be stopped during logging
a source
May not be useful for detecting flow behind casing
when pressure differentials too low
Pipe Analysis Survey
Electromagnetic
Thickness Survey
Available from most major logging companies
Developed specifically to evaluate downhole
casing damage
Can distinguish between internal and external
casing damage
Can detect and locate small defects (1/8-inch
diameter) in casing
Offers only method of detecting defects on the Cannot detect small casing defects (less than J -inch
Offered only by a select few well logging companies
If tubing removal necessary, requires removal of we/I
frnm service for extended period
outer string of double casing string
Mechanical Caliper
Logging
Borehole Television
High resolution caliper provides very accurate
record of condition of casing interior
Log can be run in short amount of time
Log can be run in either tubing or casing
diameter)
If tubing removal necessary, requires removal of well
from service for extended period
Difficult to distinguish true cause of fog anomalies
Requires availability of baseline log against which
comparison is made to subsequent logs
Offered only by a select few well fogging companies
May not detect small-diameter (1 /2-mch} defects
Difficult to locate vertical splits or cracks in casing
High resolution caliper offered only by a select few
well logging companies
Provides for direct visual inspection of downhole Well fluid must be free of suspended material
conditions
If tubing present, must be removed
Video tape recording provides for ease of replay
and comparison with other logs Operation requires removal of well from service for
extended period
Service not offered by commercial well logging com-
panies, specialized contractor necessary
Cannot be run in high temperature/pressure envi-
ronments
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Table 2. (Continued)
Method Advantages
Disadvantages
Borehole Televiewer Provides easily recognizable image of casing If tubing present, must be removed
interior
Provides either photographic or videotape record Operation requires removal of welt from service for
extended period
Limited interpretation necessary
Technique relatively slow
Can operate in less favorable environments than
borehole television Service not offered by commercial welt fogging com-
panies, specialized contractor necessary
Flow rates must be high enough for ffowmeter to
function
Ffowmeter Surveys Log can be run weither tubing or casing
Possible to estimate volume of flow from leak
Injection rate must be held constant for proper inter-
Log run during injection, tittle disruption of service pretation
Available from most major logging companies Requires professional service, equipment and inter-
pretation
Radioactive Tracer Log can be run in either tubing or casing Requires use of radioactive tracer
Surveys
Log run during injection, little disruption of service Requires professional service, equipment and inter-
pretation
Available from most ma/or logging companies
Cement Bond Log- Infers presence of channels behind casing
9'r>9
Available from most major logging companies
// tubing present, must be removed
Cannot be used to find leaks or determine fluid
movement
Many factors affect log validity
Requires professional service, equipment and inter-
pretation
Interpretation complicated and not standardized
within industry
David M. Nielsen and Linda Aller are with the National Water Well Association,
Worth/ngton, OH 43085.
Jerry T. Thornhill is the EPA Project Officer (see below).
The complete report entitled "Methods for Determining the Mechanical Integrity
of Class II Injection Wells," (Order No. PB 84-215 755; Cost: $23.50, subject to
change) will be available only from:
National Technical Information Service
5285 Port Royal Road
Springfield, VA 22161
Telephone: 703-487-4650
The EPA Project Officer can be contacted at:
Robert S. Kerr Environmental Research Laboratory
U.S. Environmental Protection Agency
P.O. Box 1198
Ad», OK 74820
United Stales
Environmental Protection
Agency
Official Business
Penalty for Private Use $300
Center for Environmental Resea
Information
Cincinnati OH 45268
CAS*' It
U S GOVERNMENT PRINTING OFFICE, 1984 — 759-015/7801
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