U.S. patent number 3,565,171 [Application Number 04/769,906] was granted by the patent office on 1971-02-23 for method for producing shale oil from a subterranean oil shale formation.
This patent grant is currently assigned to Shell Oil Company, New York, NY. Invention is credited to Philip J. Closmann.
United States Patent |
3,565,171 |
|
February 23, 1971 |
METHOD FOR PRODUCING SHALE OIL FROM A SUBTERRANEAN OIL SHALE
FORMATION
Abstract
A method for producing shale oil from a subterranean oil shale
formation wherein a chimney of fragmented oil shale is formed in
the formation by exploding a relatively high energy explosive
device therein, the chimney having a substantially void space
formed at the top thereof. A liquid is flowed through the voids
formed between the oil shale fragments, the liquid being adapted to
selectively bypass small voids and plug larger voids formed between
the fragments at least in the substantially vertical central
portion of the chimney. Hydrocarbons at substantially the top of
the chimney are ignited and a combustion supporting fluid is flowed
into the chimney at substantially the top thereof, thereby
advancing a combustion front down the chimney to substantially the
bottom thereof. The fluid flow path of the fluid supporting the
combustion tends to be substantially confined to the vertical
outlying portions of the chimney and the untreated small voids
within the chimney until the heat from the combustion front
thermally mobilizes the liquid plugging the larger voids thus
decomposing the plugging liquid thereby pyrolyzing substantially
all of the fragmented oil shale along a substantially horizontal
level within the chimney without the combustion front bypassing the
portions of the fragmented oil shale adjacent to the small voids as
the combustion front proceeds down the chimney.
Inventors: |
Philip J. Closmann (Houston,
TX) |
Assignee: |
Shell Oil Company, New York, NY
(N/A)
|
Family
ID: |
25086856 |
Appl.
No.: |
04/769,906 |
Filed: |
October 23, 1968 |
Current U.S.
Class: |
166/247; 166/256;
166/295 |
Current CPC
Class: |
E21C
41/24 (20130101); E21B 43/243 (20130101) |
Current International
Class: |
E21B
43/243 (20060101); E21B 43/16 (20060101);
E21b () |
Field of
Search: |
;166/247,256,258,260,268,272,294,295 |
References Cited
[Referenced By]
U.S. Patent Documents
Primary Examiner: Stephen J. Novosad
Attorney, Agent or Firm: J. H. McCarthy L. J. Bovasso
Claims
I claim:
1. In a method for producing shale oil from a subterranean
formation comprising the steps of: placing a relatively high energy
explosive device within the formation; exploding the relatively
high energy explosive device within the oil shale formation,
thereby forming a cavity within the oil shale formation having a
roof beneath the overburden which subsequently collapses to form a
chimney of fragmented oil shale within the oil shale formation,
said chimney having a substantially void space formed adjacent to
the top thereof; flowing a liquid through voids formed between said
oil shale fragments in said chimney, said liquid being adapted to
bypass small voids and selectively plug larger voids formed between
said oil shale fragments at least in the substantially vertical
central portion of said chimney; igniting hydrocarbons at
substantially the top of said chimney; and flowing a
combustion-supporting fluid through said chimney at substantially
the top thereof thereby advancing a combustion front down said
chimney to substantially the bottom thereof, said fluid flow path
of said combustion-supporting fluid tending to be substantially
confined to the vertical outlying portions of said chimney and the
untreated small voids within said chimney until the heat from said
combustion front thermally mobilizes the liquid plugging said
larger voids thus decomposing said plugging liquid thereby
pyrolyzing substantially all of the fragmented oil shale along a
substantially horizontal level within said chimney without said
combustion front bypassing the portions of said fragmented oil
shale adjacent to said small voids as said combustion front
proceeds down said chimney.
2. The method of claim 1 including the step of recovering shale oil
displaced from said combustion front.
3. The method of claim 1 including: the step of extending at least
a central well from a surface location to a first point adjacent to
a substantially vertical central portion of said chimney; and
subsequently flowing said liquid and said combustion-supporting
fluid through said well and into said chimney.
4. The method of claim 3 wherein the step of flowing a liquid
through said voids includes the step of flowing said liquid from a
plurality of vertical positions within said central well into said
chimney.
5. The method of claim 1 wherein the step of flowing said liquid
includes flowing a liquid containing dispersed material which tends
to cause the inflowing liquid to bypass said small voids and flow
through said larger voids.
6. The method of claim 1 wherein the step of flowing said liquid
includes flowing a liquid having a density differing from the
formation fluid being displaced from within the chimney in a manner
such that gravity tends to segregate the inflowing liquid toward
the nearest vertical extremity of the chimney.
7. The method of claim 1 wherein the step of flowing said liquid
includes flowing a liquid which is capable of substantially
solidifying in situ thereby materially reducing the permeability of
the larger voids in which it is present.
8. The method of claim 7 wherein the step of flowing a liquid
capable of substantially solidifying in situ includes flowing a
liquid capable of being thermally converted from a substantial
solid to a mobile fluid at a temperature between about 400.degree.
F. and 1,200.degree. F.
9. The method of claim 8 wherein the step of flowing a
combustion-supporting fluid includes the step of flowing a heated
fluid at a temperature exceeding the thermal conversion temperature
of the substantially solidified liquid formed in situ within said
larger voids.
10. The method of claim 8 including the step of terminating the
inflowing of liquid when a layer of the liquid extends over a
significantly large proportion of the central cross-sectional area
of the chimney and allowing said inflowing liquid to solidify in
situ prior to igniting said hydrocarbons.
11. The method of claim 10 including the steps of repeating the
steps of flowing said liquid and terminating the inflowing of said
liquid from a first point within said chimney to an additional
point within said chimney closer than than said first point towards
the center of said chimney.
12. The method of claim 11 wherein said first point is a point
substantially adjacent to the bottom vertical central portion of
said chimney and said repeated steps move upwardly within said
chimney along said vertical central portion thereof.
13. The method of claim 11 wherein said first point is a point
substantially adjacent to the top vertical central portion of said
chimney and said repeated steps move downwardly within said chimney
along said vertical central portion thereof.
14. The method of claim 1 including the step producing
substantially all of the liquids present at the bottom of said
chimney after forming said chimney and prior to flowing a liquid
through said voids so that most of the fluid remaining in said
chimney is a gas.
15. The method of claim 1 wherein the step of flowing a liquid
through said voids includes the step of flowing a foaming
thermosetting resin formulation through said voids.
16. The method of claim 1 including the step of injecting a fluid
adapted to wet preferentially oil shale fragments adjacent said
small voids prior to flowing said liquid through said voids.
Description
The invention relates to an improved method for producing shale oil
from a subterranean oil shale formation, and more particularly, to
producing oil from fragmented oil shale within an oil shale
formation.
2. Description of Prior Art
The use of contained nuclear explosions has been proposed in
subterranean oil shale formations in an attempt to break up the oil
shale formation so that shale oil can be recovered from the rubbled
zone by known techniques, such as in situ retorting.
Experience has shown that when a relatively high energy device,
such as a nuclear bomb, is exploded within a subterranean earth
formation, an almost spherical cavity filled with hot gases is
formed. This cavity expands until the pressure within the cavity
equals that of the overburden. On cooling, the roof of the cavity
collapses since, generally, it cannot support itself, and a
so-called "chimney" develops. Chimney growth ceases when the rock
pile substantially fills the cavity, or, a stable arch develops. In
both cases, a substantially void space is formed below the
overburden and above the rubble contained within the chimney.
Surrounding the chimney is a fractured zone which results from the
shock of the nuclear explosion.
However, in any chimney of rubble or fragmented oil shale formed by
the explosion of a relatively high energy device, the occurrence of
large blocks of rock or oil shale indicates large void volumes
distributed throughout the chimney. In an in situ flow process for
recovering shale oil from such a chimney of rubble, these voids
result in significant bypassing of injected and produced fluids,
leaving large portions of the rock untreated.
It is an object of this invention to provide an improved method for
recovering shale oil from a fragmented zone within a subterranean
oil shale formation.
It is a further object of this invention to provide a method for
recovering shale oil from an oil shale formation by advancing a
combustion front uniformly down a chimney or rubble formed within
the formation.
These objects are preferably carried out by exploding a relatively
high energy explosive device within a subterranean oil shale
formation thereby forming a chimney of oil shale fragments therein,
the chimney having a substantially void space formed at the top
thereof. A liquid is flowed through the voids formed between the
oil shale fragments, the liquid being adapted to selectively bypass
small voids and plug larger voids formed between the fragments at
least in the substantially vertical central portion of the chimney.
Hydrocarbons at substantially the top of the chimney are ignited
and a combustion supporting fluid is flowed into the chimney at
substantially the top thereof thereby advancing a combustion front
down the chimney to substantially the bottom thereof. The fluid
flow path of the combustion supporting fluid tends to be
substantially confined to the vertical outlying portions of the
chimney and the untreated small voids within the chimney until the
heat from the combustion front thermally mobilizes the liquid
plugging the larger voids thus decomposing the plugging liquid
thereby pyrolyzing substantially all of the fragmented oil shale
along a substantially horizontal level within the chimney without
the combustion front bypassing the portions of the fragmented oil
shale adjacent to the small voids as the combustion front proceeds
down the chimney.
BRIEF DESCRIPTION OF THE DRAWING
FIG. 1 is a vertical cross-sectional view of an oil shale formation
prior to detonating a relatively high energy explosive device
therein;
FIG. 2 is a vertical cross-sectional view of the oil shale
formation of FIG. 1 after the explosive device has been
detonated;
FIG. 3 is a vertical cross-sectional view of the final rubble zone
created by the detonation of the explosive device of FIG. 1;
FIG. 4 is a vertical cross-sectional view of the treatment of the
rubble zone of FIG. 3 in accordance with the teaching of this
invention;
FIG. 5 is a vertical cross-sectional view of single-well recovery
of shale oil from the treated rubble zone of FIG. 4;
FIG. 6 is a vertical cross-sectional view of dual-well recovery of
shale oil from the treated rubble of FIG. 4; and
FIG. 7 is a vertical cross-sectional view of an alternate treatment
of the rubble zone of FIG. 3 in accordance with the teachings of
the invention.
DESCRIPTION OF THE PREFERRED EMBODIMENTS
FIG. 1 shows a subterranean oil shale formation 11 having a
relatively high energy explosive device 12 located therein.
Explosive device 12 may be nuclear or nonnuclear. When a relatively
high energy explosive device, such as a nuclear bomb, is detonated
within an oil shale formation, a strong shock wave from the
explosive device begins to move radially outwardly, vaporizing,
melting, crushing, cracking, and displacing the oil shale formation
11. After the shock wave has passed, the high-pressure vaporized
material expands, and a generally spherical cavity, such as the
cavity 14 in FIG. 2, is formed which continues to grow until the
internal pressure is balanced by the lithostatic pressure. The
cavity 14 persists for a variable time depending on the composition
of the oil shale formation 11, then collapses to form a chimney 15
(FIG. 3). Collapse progresses upwardly until the volume initially
in cavity 14 is distributed between the fragments of the oil shale
of formation 11. The size of the cylindrical rubble zone (i.e., the
"Chimney" 15) formed by the collapse of the cavity 14 may be
estimated from the depth and explosive yield of the explosive
device 13 and the properties of the formations 11 and 16. A
substantially void space 13 is formed at the top of chimney 15.
A zone of limited permeability 17 within the fragmented oil shale
formation 17 is also formed surrounding chimney 15 as seen in FIG.
3. The permeability of this zone 17 may be preferably increased by
surrounding the explosive device 12 with a plurality of explosive
devices of lesser energy and subsequently detonating the lesser
energy devices in the manner discussed in my copending application
Ser. No. 735,684, filed Jun. 10, 1968.
After forming chimney 15, it may be desirable to extend a well
borehole 18 to a point adjacent to the bottom of the chimney 15.
Fluids which are apt to be encountered within such a zone (i.e., at
the bottom of chimney 15) are liquid and/or gaseous petroleum
products and/or steam and/or water. Particularly where petroleum
fluid is encountered, it may be desirable to produce substantially
all the liquid phase present at the bottom of chimney 15 so that
most of the fluid remaining in the fragmented zone or chimney 15 is
gaseous petroleum or air.
Referring now to FIGS. 4 and 5, the invention disclosed herein is
illustrated as preferably applied to such a fragmented zone in
which most of the fluid remaining in the chimney 15 is mainly a
gas. The same well borehole 18, preferably cased at casing 19,
cemented therein, if desirable at cementing 20, may be used to
inject a liquid down tubing string 22 into the oil shale fragments
21 disposed at the bottom of chimney 15. The liquid is preferably
pumpable and adapted to solidify in situ. Thus, each portion of the
inflowed liquid is allowed to solidify, between the series of such
injections, in order to selectively plug the central portion of the
chimney. Preferably then, a first injection is made at the bottom
of chimney 15 with the liquid allowed to solidify, then subsequent
injections are made upwardly within chimney 15 to substantially the
top thereof by selectively opening casing 19 as is well known in
the art.
The injected liquid is one which tends to flow into the larger
voids and channels in the central portion of the chimney 15 and may
be a foaming and thermosetting resin. Such materials, by foaming in
situ, increase the pressure gradient necessary for flow through
such large void spaces and channels.
After the selective plugging of preferably a substantial portion of
the vertical central portion of chimney 15, as indicated by a
solidified or treated zone 23 of relatively low permeability as in
FIG. 5, a tubing string 22 is packed off as at packers 24 and 25
below perforations 26 near the top of the chimney and above the
bottom of tubing string 22, respectively. Packer 24 is preferably
removed or unseated to provide a path of fluid communication with
perforations 26 within the treated zone 23.
After igniting the hydrocarbons present at the top of chimney 15,
by any suitable means, such as by downhole heating means, a
combustion front 27 is initiated and advanced downwardly towards a
production point near the bottom of chimney 15. This may be
accomplished by circulating a heated combustion supporting fluid
down casing 19, through perforations 26 and into the fragmented oil
shale 21 within chimney 15. The initial flow paths of the heated
fluid are confined mainly to the outlying portions of chimney 15,
that is, the untreated zone 28 of relatively high permeability as
indicated by the direction of the major portion of the arrows in
FIG. 5 and also to the untreated smaller voids within the chimney
15, until the heat from the combustion front thermally mobilizes
the plugging material that was formed within the larger voids in
treated zone 23.
By the time the plugging material decomposes, the relatively slow
advance of combustion front 27, and the resultant gradual heating
of all the rocks within the remaining fragmented zone of chimney
15, initiates the pyrolysis of the kerogen in the larger oil shale
fragments. The overall effect is a pyrolysis of substantially all
the fragmented oil shale material without a bypassing of the
portions of fragmented oil shale material adjacent to smaller voids
through which the flow resistance is significantly larger than that
within the larger voids.
Thus, as illustrated in FIG. 5, at the top of chimney 15, between
void space 13 and combustion of front 27, a zone A is formed
depleted of oil and plugging material. A partially depleted zone B
is formed between combustion front 27 and the bottom of chimney 15.
The preferred path of hot combustion products and entrained oil
shale is indicated at 29.
Numerous types of pumpable liquids may be used to selectively
permeate and temporarily plug the larger voids between oil shale
fragments 21 within chimney 15. Suitable materials include fluid
mixtures containing the components of polyurethane,
ureaformaldehyde, melamine formaldehyde, and the like types of
foaming resin formulations. As the foam begins to form, the gas
entrained within the liquid tends to divert the foams from the
small voids and keeps them within the larger voids where they
remain until the liquid components solidify. In a gas-filled
fragmented zone, the relatively higher density of such a foam
causes it to form a layer along the bottom of the gas-filled
zone.
The plugging liquid may also be a liquid resin containing filler
particles of sizes such that flow through smaller pores and
channels is inhibited. Such formulations may include solutions of
the components of resin, such as epoxy resins, phenol-formaldehyde
resins, and the like resin formulations containing particles like
shredded rubber, walnut shells, wood fibers, etc., of the types
used as conventional lost-circulation controlling materials in
working wells.
It may also be desirable to inject a fluid adapted to wet
preferentially the oil shale material. Such preferentially wetting
formulations may comprise aqueous surfactants which tend to contact
the smaller pore spaces and block them off during a subsequent
injection of resin. The presence of the liquid surfactant phase on
the walls of the oil shale fragments adjacent to the smaller void
spaces inhibits the wetting of the oil shale fragments by the resin
at least for a time and to an extent sufficient to divert the resin
into the larger channels and voids. The presence of the liquid
surfactant phase may, in some cases, be useful in causing reaction
of the injected resinous fluid. Such a wetting fluid may be
injected into the chimney 15 down the annulus formed between casing
19 and tubing string 22 as discussed hereinabove with respect to
FIG. 5.
The combustion-supporting fluid adapted to be injected into chimney
15 may be heated prior to circulation by means of a heating device
30. In other words, the fluid is pumped by means of a pump or
compressor 31 through heating device 30 and into the annulus formed
between tubing string 22 and casing 19. The fluid then flows
through perforations 26 and into the zone a of chimney 15. Oil
shale pyrolysis products are removed at the bottom of chimney 15 up
tubing string 22, through heat exchanger 32 and into separator 33
where the oil and gas components are separated as is well known in
the art. At least some makeup gas or preferably air is added at,
for example, pump 31.
Referring now to FIG. 6, a preferred arrangement for producing
shale oil from chimney 15 utilizing at least one production well
and one injection well is shown. Here, like numerals refer to like
parts of FIG. 5. The fluid from heater 30 is injected into
injection well 34, cased and casing 35, through tubing string 36.
The fluid exits past packer 37 and enters the void space 13 of
chimney 15. Oil shale pyrolysis products are produced up the casing
38 of production well 39 and into heat exchanger 32.
Where the fragmented zone within chimney 15 is filled with a
relatively dense liquid, such as water, by using a relatively
low-density formulation, such as a solution of
melamine-formaldehyde resin components containing shredded rubber,
the formation of treated zone 23 may be accomplished by injecting
the foaming formulation near the top as illustrated in FIG. 7,
while producing dense liquid from near the bottom of the chimney.
The setting time of the resin components should be adjusted so that
the treated layer extends down through the chimney to near the
bottom before the foaming formulation becomes immobile. Thus,
tubing 22 is packed in casing 19 by means of packers 19a as is well
known in the art. Shale oil is then produced from the treated
chimney 15 up tubing 22 in the manner discussed hereinabove with
respect to FIGS. 5 and 6. The injected formulation passes from
casing 19 out perforations 19b and into the top of chimney 15.
Alternatively, if the chimney of rubble 15 is liquid filled
initially, then the flow of injected resinous fluid may be
controlled by adjusting its density to be below of the filling
liquid, such as water. The chimney 15 may then be filled upwardly
in a series of steps, beginning at the bottom, as disclosed
hereinabove with respect to FIG. 4.
Because of the large rubble volume to be so treated in chimney 15,
the foaming resin formulation may be injected at a number of
vertical positions from the same well (i.e., either well 18 or 34)
by either selectively opening well 18 at different vertical
positions in chimney 15 or by extending well 34 downwardly into
selective vertical positions in chimney 15.
Alternatively, two or more wells may be drilled to communicate with
different levels within chimney 15. A limited amount of the foaming
resin formulation may be then injected into each of these wells to
treat a specified region of the chimney 15.
One advantage of injecting the foaming resin formulation through a
central well is that, by carefully regulating the quantity of such
injected materials, the outer portions of the chimney of rubble 21,
i.e., zone 28, remain substantially untreated. Injected fluids then
tend to flow preferentially near the walls of the chimney 15 but
not beyond and improve the overall sweep efficiency of the flow
process.
* * * * *