PROGRESS REPORT ON THE GEOKINETICS HORIZONTAL IN SITU RETORTING PROCESS M. A. Lekas Geokinetics Inc. 280 Buchanan Field Road Concord, CA 94520 Geokinetics Inc., in cooperation with the U. S. Department of Energy, is engaged in developing an in situ process for the extraction of shale oil. The process is designed specifically for areas where the oil shale beds are relatively thin and close to the surface. We call this technique the LOFRECO process. Geokinetics is a very small company, and does not have the resources for massive capital expendi tures ahead of production. Therefore, we set out to develop a process with low front end costs. The result was the LOFRECO process - LOFRECO being an acronym for Low Front End Cost. LOFRECO truly lives up to its name. Front end costs are minimal, as most of the expenditures are in the form of operating costs. In the process, a pattern of blastholes is drilled from the surface, through the overburden, and into the oil shale bed. The holes are loaded with explosives and fired, using a carefully planned blast system. The blast results in a well fragmented mass of oil shale, with a high permeability. The void space in the fragmented zone comes from lifting the overburden, and producing a small uplift of the surface. The fragmented zone constitutes an in situ retort. (Figure 3) The bottom of the retort is sloped to provide drain age for the oil to a sump where it is lifted by a number of oil production wells. Air injection holes are drilled at one end of the retort, and off gas holes are drilled at the other end. The oil shale is ignited at the air injection wells, and air is injected to establish and maintain a burning front that occupies the full thickness of the fragmented zone . The front is moved in a horizontal direction through the fractured shale towards the off gas wells at the far end of the retort. The burning front heats the oil shale ahead of the front, driving out the shale oil, which drains to the bottom of the retort , where it flows along the sloping bottom to the oil pro duction wells. As the burn front moves from the air-in to the air-out wells, it burns the residual coke in the retorted shale as fuel. The combustion gases are recovered at the air-out wells. This gas is combustible, and could be used for power generation. Progress of the burn front is monitored by thermocouples set in thermocouple wells. Although the process was designed to retort relatively thin oil shale beds under shallow overburden, the basic horizontal burn that is being developed can be applied to a number of other situations, such as a modified in situ process in thinner oil shale beds, or as a secondary recovery process to follow after a room and pillar mining operation to recover oil from the mine pillars and from oil shales above and below the mined zone. Laboratory and pilot work was carried out at the Geokinetics facilities at Concord, California, during 1974 and early 1975, to demonstrate the technical feasibility of establishing and maintaining a horizontally moving burning front through a random sized mass of rubblized oil shale. In March of 1975, leases on oil shale lands suitable for the LOFRECO process were acquired in the Book Cliffs area, south of Vernal, Utah, on lands 228
Transcript
PROGRESS REPORT ON THE GEOKINETICS HORIZONTAL
IN SITU RETORTING PROCESS
M. A. Lekas
Geokinetics Inc.
280 Buchanan Field Road
Concord, CA 94520
Geokinetics Inc., in cooperation with
the U. S. Department of Energy, is engaged
in developing an in situ process for the
extraction of shale oil. The process is
designed specifically for areas where the
oil shale beds are relatively thin and
close to the surface. We call this
technique the LOFRECO process. Geokinetics
is a very small company, and does not have
the resources for massive capital expendi
tures ahead of production. Therefore, we
set out to develop a process with low
front end costs. The result was the
LOFRECO process - LOFRECO being an acronym
for Low Front End Cost.
LOFRECO truly lives up to its name.
Front end costs are minimal, as most of the
expenditures are in the form of operating
costs. In the process, a pattern of
blastholes is drilled from the surface,
through the overburden, and into the oil
shale bed. The holes are loaded with
explosives and fired, using a carefully
planned blast system. The blast results
in a well fragmented mass of oil shale,
with a high permeability. The void space
in the fragmented zone comes from lifting
the overburden, and producing a small
uplift of the surface.
The fragmented zone constitutes an
in situ retort. (Figure 3) The bottom
of the retort is sloped to provide drain
age for the oil to a sump where it is
lifted by a number of oil production wells.
Air injection holes are drilled at one
end of the retort, and off gas holes are
drilled at the other end.
The oil shale is ignited at the air
injection wells, and air is injected to
establish and maintain a burning front
that occupies the full thickness of the
fragmented zone . The front is moved in a
horizontal direction through the fractured
shale towards the off gas wells at the far
end of the retort. The burning front
heats the oil shale ahead of the front,
driving out the shale oil, which drains to
the bottom of the retort,where it flows
along the sloping bottom to the oil pro
duction wells. As the burn front moves
from the air-in to the air-out wells, it
burns the residual coke in the retorted
shale as fuel. The combustion gases are
recovered at the air-out wells. This gas
is combustible, and could be used for
power generation. Progress of the burn
front is monitored by thermocouples set
in thermocouple wells.
Although the process was designed to
retort relatively thin oil shale beds
under shallow overburden, the basic
horizontal burn that is being developed
can be applied to a number of other
situations, such as a modified in situ
process in thinner oil shale beds, or as
a secondary recovery process to follow
after a room and pillar mining operation
to recover oil from the mine pillars and
from oil shales above and below the mined
zone.
Laboratory and pilot work was carried
out at the Geokinetics facilities at
Concord, California, during 1974 and early
1975, to demonstrate the technical
feasibility of establishing and maintaining
a horizontally moving burning front
through a random sized mass of rubblized
oil shale.
In March of 1975, leases on oil
shale lands suitable for the LOFRECO
process were acquired in the Book Cliffs
area, south of Vernal, Utah, on lands
228
owned by the State of Utah. The oil shale
bed is approximately 30 feet thick, and has
an average grade of about 23 gallons per
ton. The beds strike in an east-west
direction and dip to the north at about
120 feet per mile. Overburden over the
shale ranges from zero to 150 feet.
(Figure 1)
The leases are located in a very
remote area, 70 miles from the nearest
settlement. Communication is by a poorly
maintained, unpaved road. There are no
power lines or telephone lines in the area.
Immediately upon acquiring the property,
field operations began. Because of the
remote location and poor communications, it
was necessary to establish a fully equipped,
self-contained living and operating
facility at the test site. In order to
move the project ahead with the minimum
delay, the experimental work began concur
rently with the construction of the camp
facilities, and the camp has grown as the
project progressed and increased in size.
The initial camp was established in April
of 1975, and was promptly christened
"KampKerogen."
Kamp Kerogen consisted
initially of three tents and outdoor cooking
and eating facilities. The field work
progressed rapidly. Two small retorts
were blasted in July of 1975, and the first
small retort was ignited on March of 1976.
Work has proceeded seven days a week, and
continued throughout the winters despite
heavy snowfall and difficult living
conditions .
Our field program has made steady
progress since its inception in the spring
of 1975. After four years of field work,
we have blasted 18 retorts, and burned
11 retorts. In the course of carrying out
our experimental work, we have produced
over 5,000 barrels of shale oil. Kamp
Kerogen has grown from three tents in the
sagebrush to a small village, with a
permanent population of 30 persons,includ
ing wives and children.
It has been demonstrated that:
1) It is possible to drill a pattern
of blastholes from the surface into the
oil shale, and fracture the shale in a
manner to establish a zone of high perme
ability in the shale, with a relatively
impermeable zone between the fragmented
shale and the surface.
2) It is possible to drill through
the rubblized material, and construct the
various wells necessary for the operation,
including air-in holes, off gas holes,
oil recovery wells and instrument wells.
3) A point ignition can be made in
the rubblized shale and expanded into a
burn front that covers the cross section
of the retort.
4) The burn front can be moved down
the length of the retort as a cohesive
temperature front, with satisfactory sweep
efficiency.
5) Produced oil can be recovered
from a well drilled to the bottom of the
rubblized zone.
We feel that the technical feasibility
of the LOFRECO process is established. We
are now engaged in optimizing the process
to make it economically feasible. This
involves :
1) Reducing the cost of rock frag
mentation. This is the single most
significant cost item in the process.
2) Improving the recovery of in-place
oil. This involves improved blasting
techniques to prepare the shale bed for
retorting, optimized burning techniques
to minimize burn-up and coking of oil in
the retort, and better oil lifting
techniques . Our target is a recovery of
50% or more of the in-place oil. Out of
11 retorts burned to date we have achieved
50% recovery on two retorts, including
the #16, which is our latest and largest.
3) Making effective use of the
combustible retort off gas to generate
electrical power.
4) Meeting all of the environmental
requirements .
229
5) Establishing a market for crude
shale oil at the refineries in Salt Lake
City; Roosevelt, Utah; or at Fruita,
Colorado. In order to make our shale oil
acceptable to these refineries, we are
investigating the feasibility of controlled
blending of shale oil with the normal
refinery feedstock, and upgrading our shale
oil by a hydrotreating process.
Our primary objectives for 1979 are
to:
1) test a number of retorting pro
cedures to optimize oil recovery,
2) burn a retort with full thickness
of the oil shale bed (30 feet) , and
3) blast a full-sized retort (200
feet wide by 200 feet long by 30 feet
thick) .
In 1980, we plan to blast a cluster
of three full-sized retorts. During 1981,we will burn this cluster, and blast a
second three-retort cluster. This second
cluster will be burned during 1981 and the
first half of 1982.
By mid-1982, we expect to have
achieved our overall program objective of
developing and testing the Geokinetics
Horizontal In Situ Retorting Process. Bythis date we should have sufficient data
on hand to evaluate the technical,
environmental, and economic feasibility of
the process. If the results are favorable,we will be in a position to construct a
full scale operating unit producing a
minimum of 2,000 barrels of shale oil
each day.
230
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232
Retort
Number
Date
Blasted
Thickness
of Shale
Blasted
Overburden
Thickness Width Length
Cross -
Sectional
Area ft2
Tons of
Broken
Shale
Date
Ignited
Barrels
of Oil
Recovered
1 7/75 10 ft. 0 ft. 10 ft. 50 ft. 100 330 9/76 56
2 7/75 3 10 10 30 30 60 3/76 28
3 1/76 10 17 20 40 200 530 7/76 82
4 2/76 10 16 20 40 200 530 2/77 146
S 2/76 11 19 20 81 220 1200 5/77 354
6 Drilled - Not Blasted
7 11/76 10 15 20 50 200 670 -
8 11/76 23 22 20 83 460 2600 - -
9 12/76 22 22 40 83 880 4900 9/77 1007
10 12/76 11 14 20 50 220 730 - -
11 3/77 12 14 20 45 240 720 4/77 272
12 3/7/ 11 31 30 50 330 1100 - -
13 6/77 11 31 30 50 330 1100 - -
14 6/77 12 29 40 70 480 2200 2/78 384
15 7/77 20 31 50 75 1000 5000 5/78 1003
16 8/77 20 41 62 87 1200 7200 8/78 2067
17 5/78 17 26 72 156 1200 13000 - -
18 7/78 17 27 108 156 1800 19000 - -
19 12/78 30 50 126 182 3800 46000 - -
FIGURE 4. SUMMARY OF DATA ON re:"ORTS 1 THROUGH 19 (to 12/31/78)
