U.S. patent number 3,753,594 [Application Number 05/075,037] was granted by the patent office on 1973-08-21 for method of producing hydrocarbons from an oil shale formation containing halite.
This patent grant is currently assigned to Shell Oil Company. Invention is credited to Thomas N. Beard.
United States Patent |
3,753,594 |
Beard |
August 21, 1973 |
METHOD OF PRODUCING HYDROCARBONS FROM AN OIL SHALE FORMATION
CONTAINING HALITE
Abstract
A method of producing hydrocarbons and optionally halite from a
subterranean oil shale formation containing zone(s) of halite, by
penetrating said formation with at least one borehole and leaching
or dissolving the halite from the formation with a solvent fluid so
as to form a cavern(s) and/or interconnected cavities, followed by
fracturization and/or rubblization of the oil shale surrounding the
caverns or cavities, and thereafter injecting into the fracturized
and/or rubblized zones, a pyrolyzing fluid to effect insitu
hydrocarbon recovery therefrom.
Inventors: |
Beard; Thomas N. (Denver,
CO) |
Assignee: |
Shell Oil Company (New York,
NY)
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Family
ID: |
22123138 |
Appl.
No.: |
05/075,037 |
Filed: |
September 24, 1970 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
Issue Date |
|
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770964 |
Oct 28, 1968 |
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Current U.S.
Class: |
299/4;
166/271 |
Current CPC
Class: |
E21B
43/281 (20130101); E21B 43/17 (20130101); C10G
1/006 (20130101) |
Current International
Class: |
E21B
43/00 (20060101); E21B 43/28 (20060101); E21B
43/16 (20060101); E21B 43/17 (20060101); C10G
1/00 (20060101); E21b 043/28 () |
Field of
Search: |
;299/4,5
;166/259,261,271,272,307 |
References Cited
[Referenced By]
U.S. Patent Documents
Primary Examiner: Wolfe; Robert L.
Claims
I claim as my invention:
1. A method of producing hydrocarbons from a subterranean oil shale
formation having halite containing zones therein comprising the
steps of:
a. penetrating a well borehole into the halite zone of the oil
shale formation;
b. injecting water down the well borehole and into the halite
containing zone to leach and withdraw halite thereby creating voids
and cavities in the formation;
c. injecting a non-combustible pyrolyzing fluid into the leached
voids and cavities to effect extraction of hydrocarbons from the
oil shale; and
d. recovering the hydrocarbons from treatment (c) above ground.
2. The method of claim 1 wherein the pyrolyzing fluid comprises
steam having a temperature sufficient to thermally fracture oil
shale adjacent the leached voids and cavities.
3. The method of claim 1 wherein at least two wells penetrate the
formation one of which functions as an injection well and one as a
production well.
4. The method of claim 2 wherein the halite is removed by steam
used also to effect hydrocarbon recovery.
5. The method of claim 4 wherein the halite and hydrocarbon are
recovered simultaneously.
Description
CROSS-REFERENCE TO RELATED APPLICATIONS
This application is a continuation-in-part of copending application
Ser. No. 770,964, filed Oct. 28, 1968 and now abandoned.
BACKGROUND OF THE INVENTION
1. Field of the Invention
This invention relates to the recovery of hydrocarbons and
optionally halite from underground oil shale formations containing
halite deposits. More particularly, it relates to hydrocarbon
recovery by in-situ thermal fluid extraction of oil shale within a
fracturized and/or rubblized portion of a subterranean oil shale
formation in and around a cavern and/or interconnected cavities
formed by leaching or dissolving, e.g., solution mining of the
halite therefrom.
2. Description of the Prior Art
Large deposits of oil in the form of oil shale are found in various
sections of the United States, particularly in Colorado and
surrounding states and Canada. Various methods of recovery of oil
from these shale deposits have been proposed and the principal
difficulty with these methods is their high cost which renders the
recovered oil too expensive to compete with petroleum crudes
recovered by more conventional methods. Mining the oil shale and
removing the oil therefrom by above-ground retorting in furnaces
presents a disposal and pollution problem and also such processes
are also generally commercially uneconomical. In-situ retorting to
convert the oil shale to recover the oil contained therein is made
difficult because of the non-permeable nature of the oil shale. The
art discloses various means of improving oil recovery of oil from
oil shale such as described in U.S. Pat. Nos. 3,400,762 or
3,437,378 or 3,478,825 and particularly various means of increasing
permeability of oil shale formations as described in U.S. Pat. Nos.
3,273,649 or 3,481,398 or 3,502,372, or copending application Ser.
No. 839,350, filed July 7, 1969. Although these references are
directed to an advancement of the art, the basic technique for
recovering oil from oil shale still requires rubblization
techniques such as by means of explosive devices, e.g., nuclear
energy which is expensive, difficult to control and presents a
radioactive contamination problem all of which are very
undesirable.
OBJECTS OF THE INVENTION
It is an object of this invention to provide an improved method for
recovering hydrocarbons from a halite containing oil shale
formation by leaching or dissolving the halite such as by solution
mining so as to form a cavern and/or interconnected cavities within
the oil shale formation.
It is a further object of the invention to effect rubblization
and/or fracturization of the halite leached oil shale formation
surrounding the cavern and/or cavities so as to form a permeable
zone thereby enhancing in-situ thermal fluid extraction (pyrolysis)
of hydrocarbons therefrom.
Still another object of this invention is to effect in-situ
pyrolysis to produce hydrocarbons from oil shale subjected to
leaching, rubblization and fracturization as indicated in the
previous two paragraphs, and subsequently recovering the
hydrocarbons by suitable means.
Still another object of the present invention is to recover
watersoluble minerals from a rich halite containing oil shale
formation that may be removed during the leaching and/or solution
mining, rubblization and/or fracturization, and/or pyrolysis
processes.
Still another object of the present invention is to sequentially
and/or simultaneously recover halite and hydrocarbons from halite
containing oil shale formations that may be removed during the
leaching and/or solution mining, rubblization and/or fracturization
and/or pyrolysis processes.
Other objects of the invention will be apparent from the following
description.
SUMMARY OF THE INVENTION
The present invention is directed to recovery of hydrocarbons and
optionally halite from a halite containing oil shale formation by
the following steps: (1) subjecting a rich halite zone(s) of an oil
shale formation to a leaching, dissolving or solution mining
process so as to remove the halite, thereby creating porosity to
allow for thermal expansion of the oil shale and establish
communication through the treated zone(s), (2) effecting in said
leached zone(s) rubblization and/or fracturization so as to form
zone(s) of rubblized and/or fractured oil shale with large surface
area for more efficient heat treatment by in-situ thermal fluid
extraction (pyrolysis) and (3) injecting into the rubblized and/or
fracturized oil shale zone(s) a pyrolyzing fluid to effect
hydrocarbon recovery.
The halite and hydrocarbons may be recovered sequentially or
simultaneously and if the latter, the two products can be separated
by suitable means such as settling or solvent extraction above
ground. The oil shale formation may contain more than one zone of
rich halite which zones may be separated by impermeable oil shale
layers of several feet to several hundred feet and each of these
halite layers or zones can be leached or dissolved or solution
mined in accordance with the process of the present invention.
The first or initial step should be so designed to create a cavern
or interconnecting cavities in the halite bed(s) or zone(s) by
dissolving, leaching or solution mining techniques through at least
one borehole penetrating said formation. Leaching can be effected
by cold or hot aqueous solutions either at atmospheric or elevated
pressures. When hot solutions are used such as hot water and/or
steam, more rapid dissolution is effected to produce void spaces in
the oil shale formation thereby providing and enhancing well
communication, space for thermal expansion of the shale, and
greater surface contact with subsequent pyrolyzing fluid.
If necessary, fracturing the formation either before or after
leaching by conventional means such as hydrofracturing, explosive
means, nuclear means, etc., may be desirable. The leaching
solutions can contain chemical agents to enhance dissolution of the
minerals.
Leaching or solution mining of the halite can be accomplished by a
suitable solution mining technique such as described in U.S. Pat.
Nos. 2,618,475; 3,387,888; 3,393,013; 3,402,966; 3,236,564;
3,510,167 or Canadian patents 832,828 or 832,276 or as described in
copending application Ser. No. 2,765, filed Jan. 14, 1970. Spalling
and rubbling can be accomplished by the method described in U.S.
Pat. No. 3,478,825 or by other means such as by hydraulic
explosive, nuclear, electrical means. Preferably rubblization is
accomplished by hot fluid circulation through two caverns causing
the two walls to spall and fracture. In-situ thermal recovery of
oil can be effected by a pyrolyzing fluid such as steam and/or hot
water or solvent extraction means.
The circulation of a pyrolyzing fluid not only effects oil recovery
but also effects thermal rubbling and/or fracturization. Also, if
the pyrolyzing fluid such as steam is used to extract and recover
oil, more halite may be dissolved perpetuating the process.
The term "pyrolyzing fluid" is used to refer to a liquid or gas
which by means of thermal, chemical and/or solvent action,
interacts with the kerogen components of an oil shale to produce
and entrain hydrocarbon such as oil. Such a fluid can be comprised
of hot fluids such as hot water or steam or mixtures of hot water
and steam, hot hydrocarbons and/or mixtures of such fluids with
chemicals such as acids, e.g., HCl and/or organic solvents,
benzene, toluene, cumene, phenol, etc. The kerogen pyrolyzing fluid
can be heated by surface or borehole-located heating devices. The
kerogen-pyrolyzing fluid can advantageously comprise or contain a
solvent for the halite, such as a steam condensate, having a
temperature such as of at least 100.degree.F, such as from about
450.degree.F to above about 1,500.degree.F and preferably from
about 550.degree.F to 1,000.degree.F. Where the kerogen-pyrolyzing
fluid contains or forms aqueous components, its circulation through
the treated oil shale formation can enlarge the cavern, by solution
mining the soluble minerals, while shale oil is being produced.
Also, simultaneously or sequentially, pyrolyzing and oil extracting
fluids can be used such as steam followed by a solvent such as
phenol or benzene.
BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 is a vertical sectional view, partly diagrammatic, of an
embodiment of the invention showing a formation penetration by more
than one well; and
FIG. 2 is a sectional view of an embodiment of the invention, the
formation being penetrated by a single well.
DESCRIPTION OF THE PREFERRED EMBODIMENT
Referring to FIG. 1 of the drawing, a plurality of well boreholes
are shown penetrating into a subterranean oil shale formation 9
which contain rich zones of halite 10, 10a and 10b. An injection
well borehole 11 is shown extending into oil shale formation 9 and
rich halite zone(s) 10 or multizones such as 10a and 10b that are
located within the oil shale formation 9 and are also encountered
by well borehole 12. Well boreholes 11 and 12 are illustrated by
having casings 13 through 14, respectively, cemented in place in
their respective boreholes by suitable sealants 15 through 16,
respectively. Although only a single injection well borehole 11 and
a single production well borehole 12 have been illustrated,
obviously various combinations of one or more injection and
production wells may be provided by one skilled in the art.
Fluid communication between well boreholes 11 and 12 (FIG. 1) and
the zones rich in halite therebetween may be established by
solution mining a cavern or cavities 23, through the soluble
mineral zones. Communication can be enhanced by means of
conventional hydraulic, electric, and/or explosive fracturing
techniques, all well known in the art. Where, for example,
subterranean stresses in and around soluble mineral zones 10, 10a,
and 10b are conducive to the formation of horizontal fractures, the
fluid communication between well boreholes 11 and 12 and the halite
can be established by a conventional hydraulic fracturing
technique. Referring to FIG. 1, after fluid communication has been
established between a pair of wells, aqueous leaching or solution
mining liquid is injected through tubing 17 down well borehole 11,
out through perforations 18 opposite any or all of the soluble beds
through the bed 10, 10a and/or 10b up borehole 12 through tubing
via perforation 19 creating a leached cavern 23. The aqueous liquid
may comprise water and/or steam or aqueous solutions of acid or
acid-forming materials and is circulated at pressures either above
or below the over-burden pressure. The circulating aqueous liquid
dissolves the halite which is recovered from the fluid flowing out
of well borehole 12, for example, by conventional evaporation
and/or precipitation procedures.
Fluid communication can also be established in one borehole between
at least two spaced portions of the well borehole and the halite
(as for example, in FIG. 2 communication is through the tubing
strings, the ends of which are open to the halite and some distance
apart). Thus, a single well may be utilized by a dual zone
completion arrangement as shown in FIG. 2 such that fluids can be
injected at one point of the well and produced from another point
of the same well. In FIG. 2, the wellbore is 26, the casing is 27,
the sealant is 28, within the casing are the injection tubing
string 29 and production tubing string 30, the borehole 26
penetrates oil 0shale formation 9 with halite zone(s) 10 or
multizones 10a and 10b.
Fracturing pressures are generated within the oil shale formation 9
while lower pressures are maintained within the cavern 23 which is
formed within oil shale formation 9 by the removal of the halite.
These pressures are preferably generated by merely circulating hot
fluid through cavern 23. As the walls of the cavern(s) 23 (23a FIG.
2) are heated kerogen is pyrolyzed within the cavern walls and the
pressures of the pyrolysis products increase until portions of the
walls are spalled into the cavern 23 creating a rubblized zone 24
(24a FIG. 2) and surrounding fracture area 25 (25a FIG. 2).
Alternatively, fracturization and/or rubblization can be
accomplished by conventional means such as hydraulic, explosive
means and the like. To provide additional void space, if necessary,
further leaching can be conducted.
Finally, a kerogen-pyrolyzing fluid such as steam is circulated
from well borehole 11 (FIG. 1) through the rubblized zone 24 and
fractured zone 25 of oil shale formation 9 and out of well borehole
12. Hydrocarbon materials are then recovered from the heated fluid
circulating out of well borehole 12 by means well known in the art.
Removal of hydrocarbons from the oil shale provides additional void
space enlarging the original rubblized zone, perpetrating the
process. Similar techniques can be applied to single wells as shown
in FIG. 2.
Conventional equipment and techniques, such as heating means,
pumping means, separators and heat exchangers may be used for
pressurizing, heating, injecting, producing and separating
components of the heated fluid circulating through the oil shale
formation 9. The production of the fluid may be aided by downhole
pumping means, not shown, or restricted to the extent necessary to
maintain the selected pressure within the oil shale formation
9.
The fluid circulated through rubblized zone 24 and fractured zone
25 (FIG. 1) to recover oil shale from oil shale formation 9 may
comprise any heated gas, liquid or steam. Oil shale reactive
properties may also be imparted to the circulating fluid as
discussed hereinabove.
Where the oil shale formation contains a zone rich in halite in
which zone the halite occur in the form of adjacent but discrete
nodules or lenses 31, or the like, the present process is applied
as described above. In this situation, the caverns comprise a
network of relatively small cavities that are interconnected by
fractures.
It is understood that various changes in the detailed described to
explain the invention can be made by persons skilled in the art
within the scope of the invention as expressed in the appended
claims.
* * * * *