United States
Environmental Protection
Agency
Industrial Environmental
Research Laboratory
Cincinnati OH 45268
Research and Development
EPA-600/S7-84-050 Apr. 1984
Project Summary
Infiltration and Permeability
Testing at Geokinetics
Oil Shale Site
Edward W. Holyman and George W. Quinn
Infiltration (double-ring) and pressure
permeability (packer) tests were
conducted in or near true in-situ oil
shale retorts and at adjacent
undisturbed locations to obtain com-
parative data to evaluate the potential
for groundwater pollution due to
increased fluid migration resulting from
this retorting methodology. Tests were
performed at the Geokinetics' oil shale
site located in Section 2, Township 14
South, Range 22 East, Uintah County,
Utah.
Three infiltration test sites were
selected for study. Two of the sites
were located in disturbed surface soils
overlying two retorts. The third site was
situated in nearby undisturbed soils
similar to those found at the two
retorts. Pressure permeability tests
were conducted in a newly constructed
angle hole and in an existing core hole.
The angle hole was drilled so the perme-
ability measurements could be made
near and below a burned retort. An
existing core hole in nearby undisturbed
rock was tested for comparison.
Test results suggest a slight increase
in surface infiltration rates and
hydraulic conductivity in or near the
retort areas. This will allow additional
surface waters to enter into and pass
through the vadose zone increasing the
possibility of contact with potential
pollution sources generated by
retorting activities. However, before
drawing any conclusions regarding the
extent of threat to groundwater
resources in the area, the hydrogeologic
conditions, especially permeability of
the stratigraphic interval between
the retorts and the closest aquifer.
should be carefully defined.
Extrapolation of results from this study
to other sites is valid only to the extent
that retorting and hydrogeologic condi-
tions can be defined to be the same as
for this test site.
This Project Summary was developed
by EPA's Industrial Environmental Re-
search Laboratory, Cincinnati, OH, 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
This report discusses the results of
Kaman Tempo's infiltration and permea-
bility testing at the Geokinetics' oil shale
site located in Section 2, T14S, R22E,
Uintah County, Utah. Comparative
evaluations for each of the testing
methods were performed in areas
affected and unaffected by retort
development. All work performed herein
was conducted pursuant to EPA Contract
No. 68-03-2449.
The objectives of this research program
were to: (1) evaluate possible alteration of
surface infiltration rates due to retort
development, burning and associated
surface fracturing and uplift; and (2)
measure, by means of packer testing,
possible changes in the permeability of
rocks affected by retort development and
burning.
The Geokinetics' site was selected for
testing because of the true in-situ oil
shale retorting methodology utilized
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there. The process entails drilling a
pattern of drill holes from the surface,
through the overburden, and into the oil.
shale bed. The holes are loaded with
explosives and fired, using a
pre-determined blast system. The blast
results in a fragmented, highly
permeable mass of oil shale. The void
space in the fragmented zone comes from
lifting of the overburden that produces a
small arch in the ground surface.
The fragmented zone within the oil
shale horizon constitutes an in-situ
retort. The bottom of the retort is sloped to
facilitate drainage of the oil to a sump
where it is lifted to the surface by a
number of oil production wells. Air
injection holes are drilled at one end of
the retort and offgas holes are drilled at
the other end. The oil shale is ignited at
the injection wells. Air is then injected to
establish and maintain a burning front
that occupies the full thickness of the
fragmented zone. The front is moved in a
horizontal swell through the fractured
shale towards the offgas wells at the far
end of the retort. The hot combustion
gases from the burning front heat the
kerogen in the oil shale, inducing
destructive distillation and draining out
the oil. The oil drains to the bottom of the
retort, where it flows along a sloping
surface to the oil production wells. As the
burn front moves from the air into the
offgas wells, it burns the residual carbon
in the retorted shale as fuel. The
combustion gases are recovered at the
offgas wells. This gas is combustible and
can be used for power generation.
This study tested infiltration and
permeability characteristics of soil and
rock formations at the Geokinetics' oil
shale retorting facilities and should have
wider application in other oil shale
locales. The report is divided into four
sections: introduction, testing program,
test results, and conclusions.
Testing Program
Kaman Tempo performed the
infiltration and permeability testing at the
Geokinetics' site during September and
October, 1981. Autumn was selected for
testing in order to avoid water-saturated
soil conditions resulting from spring
snow melt and summer thunderstorms.
Frozen soil conditions and access
problems of winter were likewise avoided.
Infiltration Testing
Double-ring infiltration tests were
performed at nine focations--six
overlying burned retorts (14 and 15) and
three in undisturbed areas. The purpose
of the study was to evaluate changes in
infiltration rates due to surface heave
over the retorts. Double-ring infiltrome-
ters were selected because they provide
data that is considered representative of
the vertical component of the infiltration
flow and for their operational simplicity in
the field that facilitated multiple tests
useful 'for comparative analysis. It is
generally acknowledged that infiltration
rates determined by sprinkling a large
area are more reliable than cylinder-type
determination. However, the need for
multiple test sites and the high cost of
utilizing sprinkler infiltrometers preclu-
ded their use during this study.
Tests at all sites were conducted in the
following manner: a metal cylinder 30cm
(12 in) in diameter was driven to a depth
of approximately 15cm (6 in) into the soil
at the test site. A larger cylinder, 46cm
(18 in) in diameter, was placed
concentrically around the 30cm (12 in)
cylinder. The areas within the inner and
outer cylinders were flooded, and the rate
of recession of the water level in the inner
ring was measured by means-of a meter
staff. Tests were conducted for 90
minutes, which in the soil type tested was
considered sufficient time to obtain a
steady state condition. Care was taken to
conduct all infiltration tests on the same
soil type; namely Luhon Loam.
Pressure Permeability Testing
Pressure permeability tests were
conducted in two drill holes. Angle Hole
No. 1 was drilled between retort 24
(burned) and retort 26 (unburned) in a
manner so that it would pass within three
meters (10 feet) of the base of the burned
core of retort 24 and bottom approximate-
ly 38 meters (124 ft) below the base of the
retort. Total length of this hole is 75
meters (247 ft). (Permeability testing
could not be done in any of the burned
retorts because of residual high rock
temperature and very high permeability.)
The other drill hole tested was Core Hole
12, drilled in 1978 by Geokinetics. This
hole is vertical, was found to be in good
condition, and was suitable for testing. It
is 30 meters (100 ft) deep and is located
well enough away from any effects of
rubblizing or retorting. Both holes are NX
7.6cm (3 in) diameter and are bottomed
above the water table. The shallowest
substantial aquifer underlying the
Geokinetics' site is the Douglas Creek
Member of the Green River Formation,
approximately 244 to 274 meters fSOO to
900 ft) below the surface.
Dual packers spaced 3.6 meters (11-8
feet) apart were placed on the end of the
drill string. Subtracting the space
occupied by the packers, this resulted in
testing a 3 meter (10-foot) interval.
Testing started at the bottom of each hole
and progressed upward at intervals
approximately equal to the packer
spacing. Testing and calculation of per-
meabililty for each zone were done in
accordance with the method discussed in
Ground Water Manual published by the
U.S. Department of the Interior, Bureau of
Reclamation, 1977.
Test Results
Infiltration
Infiltration rates expressed in centi-
meters per hour were calculated directly
from field measurements. Infiltration
rates were plotted against time, resulting
in a curve showing the change in
tendency of the soil to absorb water with
time. The areas under the curves
represent the infiltration capacity or the
capacity of the soil to absorb water up to a
particular time.
Results of the infiltration tests indicate
moderate to slow infiltration rates.
Infiltration rates were slower in the
undisturbed area than over both retorts,
but the retort rates are still considered to
be slow. All plots indicate roughly the
same attainment of near-steady-state
conditions.
On the basis of eight tests, there were
no statistically significant differences in
the surface infiltration rates. The ninth
test (site C, retort 14) was not included in
the analysis. The heavy vegetative cover
producing extensive root structure within
the tested soil horizon provided pathways
for the infiltrating water, thus giving
nonrepresentative results. From the
limited amount of data developed, the
range of final infiltration rates appeared
somewhat larger overlying the retorts as
compared to the undisturbed area.
However, no statistical significance could
be developed for this apparent character-
istic nor for the slightly higher overall
infiltration rates found overlying the
retorts.
Permeability
Angle Hole No. 1 was utilized to
evaluate permeability near a burned
retort, and in the area underlying the
retort. During the aVHHng of the hole, 7.6
meters (25 feet) of rich-tar sand was
encountered at approximately 59m (195
feet). Between completion of the hole and
packer testing a substantial amount of
wax-like hydrocarbon material had
seeped into the well bore and drilf string
clogging 30n\ flOO feet> of drill pipe. This
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prevented testing of the interval between
24m and 69m (80 feet to 227 feet). A
single packer test was conducted
between 69 meters and the bottom of the
hole at 75 meters (227 and 247 feet).
Double-packer tests were conducted at 3
meter (10 foot) intervals from 24 to 3
meters (80 feet to 10 feet).
Existing core hole No. 12 was found to
be in good condition for testing and did
not penetrate the tar sand found deeper
in Angle Hole No. 1. Located 304 meters
(1,000 feet) from the nearest retort, it was
selected to provide hydraulic conductive
data for undisturbed material. Dual
packer permeability tests were run
throughout the hole.
Permeability measurements show a
good correlation with rock discontinuities
developed from core analysis. The
correlation of permeability and secondary
porosity (rock fractures) indicates that
flow through the tight oil shale
stratigraphy in this area is largely con-
trolled by these discontinuities. Permea-
bilities varied by a factor of 1,000 from
nearly impermeable rock at the bottom of
the angle hole to moderately fractured
rock near the surface. Conductivity
values decrease very slightly as the angle
hole approached the burned retort 24.
In general, permeability values were
lower in the undisturbed area 304 meters
(1,000 feet) southeast of the nearest
retort. This is more apparent when you
consider that four of the seven test
sections in the undisturbed area would
not take water at all. However, where
fractures were penetrated, permeability
values were similar to or higher than
those found near the retort.
Conclusions
Surface infiltration and pressure per-
meability tests were conducted at the
Geokinetics oil shale site. Eight double-
ring infiltration tests suggest that there is
a slight increase in fluid entering the soil
profile over the retorts compared to un-
disturbed areas. However, the statistical
significance of this apparent
characteristic could not be evaluated with
the limited data compiled herein.
Pressure permeability tests near retort
24 indicated an overall increase in
hydraulic conductivity adjacent to burned/
uplifted retorts- compared with the
undisturbed area. Although permeability
values varied over a wider range tn the
undisturbed area (both higher and lower
conductivity measurements recorded)
several test sections would not take
water at all. This suggests that
permeability is controlled by secondary
porosity (rock fractures) that are
enhanced by mining operations.
Surface infiltration and near surface
permeability are the principal parameters
that govern shallow fluid migration at the
Geokinetics test site. Increased penetra-
tion of surface water and enhanced
migration through the vadose zone
increase the possibility of contact.with
and leachate generation from potential
pollution sources generated by the
mining and retorting activities. These
fluids would have a negative impact on
local groundwater quality should they
reach the saturated zone.
However, before drawing any
conclusions regarding the extent of
threat to groundwater resources in the
area, the hydrogeologic conditions,
especially permeability of the
stratigraphic interval between the retorts
and the closest aquifer, should be
carefully defined. At the test site this
interval consists of several hundred feet
of shale, marlstone, oil shale and tar
sand. Although these lithologies
normally have very low permeability, any
secondary permeability introduced by
fracturing or jointing must be defined
before it may be concluded that a signifi-
cant threat to groundwater resources
does not exist. Extrapolation of results
frem this study to other sites is valid only
to the extent that retorting and
hydrogeologic conditions can be defined
to be the same as they are for this test
site.
References
Ground Water Manual published by the
U.S. Department of the Interior, Bureau of
Reclamation, 1977. Copies can be
obtained from the Bureau's Engineering
and Research Center, P.O. Box 25007,
Denver Federal Center, Denver, Colorado
80225, Stock #024-003-00106-6.
Edward W. Hoy/man and George W. Quinn are with Kaman Tempo, Santa
Barbara, CA 93102.
Leslie G. McMillion and Edward R. Bates are the EPA Project Officers (see
below).
The complete report, entitled "Infiltration and Permeability Testing at Geokinetics
Oil Shale Site," {Order No. PB84-173 806; Cost: $8.50, subject to change) will
be available only from:
National Technical Information Service
5285 Port Royal Road
Springfield, VA 22161
Telephone: 703-487-4650
EPA Project Officer Leslie G. McMillion can be contacted at:
Environmental Monitoring Systems Laboratory
U.S. Environmental Protection Agency
Las Vegas, NV 89114
EPA Project Officer Edward R. Bates can be contacted at:
Industrial Environmental Research Laboratory
U.S. Environmental Protection Agency
Cincinnati, OH 45268
U S GOVERNMENT PRINTING OFFICE; 1984 — 759-015/7678
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United States
Environmental Protection
Agency
Center for Environmental Research
Information
Cincinnati OH 45268
Official Business
Penalty for Private Use $300
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