Oil shale formations are retorted in situ and gaseous hydrocarbon products are recovered by drilling two or more wells into an oil shale formation underneath the surface of the ground. A high energy laser beam is directed into the well and fractures the region of the shale formation. A compressed gas is forced into the well that supports combustion in the flame front ignited by the laser beam, thereby retorting the oil shale. Gaseous hydrocarbon products which permeate through the fractured region are recovered from one of the wells that were not exposed to the laser system

Bloomfield, H. S.

English

NASA Technical Reports Server

NATIONAL AERONAUTICS AND SPACE ADMINISTRATION
WASHINGTON. D.C. 20546
DEC 2 2 1977
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SUBJECT: Announcement of NASA-Owned U.S. Patents in STAR
o in In accordance with the procedures agreed upon by Code GP and Code
KSI, the attached NASA-owned U.S. Patent is being forwarded for
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The following information is provided:
U.S. Patent No. :
Government or
Corporate Employee
Supplementary Corporate
Source (if applicable)
NASA Patent Case No.
(J ,
NOTE - If this patent covers an invention made by a corporate employee
of a NASA Contractor, the following is applicable:
YES / / NO /5t7
Pursuant to Section 305(a) of the National Aeronautics and Space Act,
the name of the Administrator of NASA appears on the first page of the
patent; however, the name of the actual inventor (author) appears at
the heading of column No. 1 of the Specification, following the words
"...with respect to an invention of ..."
Bonnie L. Henderson
Enclosure
https://ntrs.nasa.gov/search.jsp?R=19780006509 2020-03-20T12:56:41+00:00Z
United States Patent [«]
Bloomfield,
[54] IN-SITU LASER RETORTING OF OIL
SHALE
[75] Inventor: Harvey S. Bloomfield, Bay Village,
Ohio
[73] Assignee: The United States of America as
[ii] 4,061,190
[45] Dec. 6, 1977
3,977,478 8/1976 Shuck ....
4,019,577 4/1977 Fitch et al
Primary Examiner — James A. Leppink
Attorney, Agent, or Firm — N. T. Musial; J.
John R. Manning
166/308
166/259
A. Mackin;
represented by the United States
National Aeronautics and Space
Administration, Washington, D.C.
[21] Appl. No.: 763,753
[22] Filed: Jan. 28,1977
[51] Int C1.2 E21B 43/24
[52] UJS. Q 166/259; 166/248
[58] Field of Search 166/248,256,259;
208/11 R; 175/11, 16, 17
[56] References Cited
U.S. PATENT DOCUMENTS
3,400,762 9/1968 Peacock et al 166/259
3,411,575 11/1968 Connally, Jr 166/259
3,493,060 2/1970 Van Dyke 175/16
3,652,447 3/1972 Yant 208/11 R
3,696,866 10/1972 Dryden 166/248
Oil shale formations are retorted in-situ and gaseous
hydrocarbon products recovered by drilling two or
more wells into an oil shale formation underneath the
surface of the ground; fracturing a region of said oil
shale formation by directing a high energy laser beam
into one of said wells and focussing said laser beam onto
said region of said oil shale formation from a laser opti-
cal system; forcing a compressed gas into said well
through which said laser beam was directed at the site
of said fracture which supports combustion in the flame
front ignited by said laser beam in the fractured region
of said oil shale, thereby retorting said oil shale; and
recovering gaseous hydrocarbon products which per-
meate through said fractured oil shale from one of said
wells through which the laser beam was not directed.
8 Claims, 1 Drawing Figure
U.S. Patent Dec. 6, 1977 4,061,190
/^x.s^/x^/A-.^/x^///'-v.//>'^/>^///^xv/^y/^ >
4,061,190
25
IN-SITU LASER RETORTING OF OIL SHALE
ORIGIN OF THE INVENTION
The invention described herewin was made by an 5
employee of the United States Government and may be
manufactured and used by or for the Government of the
United States of America for governmental purposes
without the payment of any royalties thereon or there-
for. 10
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a method for retort-
ing and obtaining hydrocarbons from underground 15
shale deposits. More particulary, the present invention
relates to a process for the in-situ laser retorting of
hydrocarbons from underground shale deposits.
2. Description of the Prior Art
In the past many methods have been devised for the
processing of fossil fuels to recover hydrocarbons val-
ues therefrom. One such method as described in U.S.
Pat. No. 3,652,447 involves first mining oil shale and
placing the oil shale, which is crushed, into an enclo-
sure. A pulsed laser beam is used to heat the bottom
layers of the oil shale in the enclosure, and air is drawn
into the bed of shale to cause eduction of gaseous hy-
drocarbons upwardly through the shale into a gas col-
lection space. The rising air and gas heat the upper ...
layers of the bed of shale thereby retorting the entire
body of shale. Gaseous products are then withdrawn
from the base of the enclosure. While this method is
applicable to the retorting of previously mined or re-
covered oil shale, it cannot be used for the in-situ retort-
 35
ing of oil shale.
Methods have been developed in the past for the
in-situ recovery and retorting of underground deposits
of oil shale. All of these methods share the following
basic steps in which a predetermined pattern of wells is 49
drilled in the oil shale formation, and the formation is
fractured to increase the permeability of the shale.
Thereafter the shale is ignited at one or more centrally
locoated wells. After ignition, compressed air is
pumped down into the ignition wells to support com- 45
bustion processes within the shale formation, and the
hot combustion gases are forced through the fractured
shale to degrade the solid organic material within the
shale to an oil product. The oil produced by the thermo-
lytic degradation process is subsequently recovered 50
through other wells. All of these techniques share the
common problems of attaining the desired degree of
permeability of the shale within the formation by frac-
turing the oil shale between previously drilled wells,
and of underground ignition anh heating of the shale. 55
In the past, a number of methods have been employed
to create a permeable shale bed which include hydraulic
fracturing, electrolinking, electropneumatic and elec-
trochemical fracturing and fracturing using conven-
tional explosives. Other techniques have used combina- 60
tions of these methods of fracturing oil shale. Thus far,
it has been necessary to recover the fractured shale in
order to simulate in-situ processing in above ground
retorts by utilizing natural gas for ignition and recycled
gas and air injection to support combustion within the 65
shale bed. Alternatively, as shown in U.S. Pat. No.
3,652,447, a laser beam can be employed to ignite the
combustion process.
One method has been developed for the in-situ retort-
ing of shale deposits as disclosed in U.S. Pat. No.
3,696,866. In this method two wellbores are drilled into
a shale deposit and an electrode is lowered into each of
the wells at a position in the shale bed. A high d.c.
voltage is then impressed across the electrodes, which
results in the formation of a conducting core in the shale
deposit. One of the electrodes is removed from one of
.the wells, and is replaced by an electrolyte solution to a
level above the core and an acid resistant electrode. A
high d.c. voltage is then impressed across the pair of
electrodes which causes electrolysis and results in the
formation of free oxygen where the conducting core
intersects the solution. With sufficient voltage, intense
heating and arcing occurs in the core of the shale thus
resulting in combustion of organic materials. Applica-
tion of the voltage is continued until the combustion
zone has completely penetrated the path between the
wellbores. This method has the disadvantage of requir-
ing the use of a high voltage source and of the necessity
of having to place an aqueous electrolyte into one of the
well bores. Moreover, and acid resistant electrode must
be used in the electrolyte solution. Accordingly, a need
continues to exist for a simpler method for conducting
the in-situ retorting of shale deposits for the eventual
recovery of hydrocarbon products.
SUMMARY OF THE INVENTION
Accordingly, one object of the present invention is to
provide a method for fracturing underground oil shale
formations to render the shale permeable such that the
in-situ retorting of the shale can be performed to effect
recovery of hydrocarbon products from the shale.
Briefly, this object and other objects of the present
invention as hereinafter will become more readily ap-
parent can be attained in in a method for the in-situ
retortingof oil shale and recovery of gaseous hydrocar-
bon products by drilling two or more wellbores into an
oil shale formation underneath the surface of the
ground; fracturing a region of said oil shale formation
by directing a high energy laser beam into one of said
wells and focussing said laser beam onto said region of
said oil shale formation from a laser optical system;
forcing a compressed gas into said well through which
said laser beam was directed at the site of said fracture
which supports combustion in the flame front ingnited
by said laser beam in the fractured region of said oil
shale, thereby retorting said oil shale; and recovering
gaseous hydrocarbon products which permeate
through said fractured oil shale from one of said wells
through which the laser beam was not directed.
BRIEF DESCRIPTION OF THE DRAWINGS
A more complete appreciation of the invention and
many of the attendant advantages thereof will be
readily obtained as the same becomes better understood
by reference to the following detailed description when
considered in connection with the accompanying draw-
ings; wherein:
The FIGURE shows an embodiment of the invention
in which an oil shale formation is fractured by use of a
laser beam and in-situ retorting of the fractured shale is
conducted.
DETAILED DESCRIPTION OF THE
PREFERRED EMBODIMENTS
The essential and important feature of the present
invention is the use of a high energy laser beam which
4,061,190
4
is directed into an oil shale formation to simultaneously
cause fracturing of the shale, thereby inducing pennea-
bility of the underground formation and ignition of the
shale within the underground formation. A compressed
gas such as air, which supports combustion, is passed 5
down into the well at the site of the fracture to force a
flame front ignited by the laser through the fracture.
Gaseous hydrocarbon products are produced by the
retorting of the shale and are withdrawn from other
associated wells which are coupled to the well through 10
which the laser beam is directed as they permeate
through the fracture zone. The type of laser apparatus
employedin the present method is not critical, and any
device which emits a beam of sufficient energy to cause
fracturing and ignition of the shale can be employed. A 15
typical laser is a high power (multiKilowatt average
power) infrared CO2 laser device. Both pulsed and con-
tinuous infrared lasers can be used.
Reference is now made to the FIGURE, which
shows an embodiment of the present method, to achieve 20
^°r ra^T ™derst*nduig of the invention. The
FIGURE shows a vertical cross-section of ground 1
containing an underlying oil shale formation 3. A weU-
bore 5 is drilled mto die ground 1 which penetrate into
the underlying shale deposit 3, and is provided with two 25
ducts 6 and 7. Central duct 6 functions as a protective
housing for a laser beam 13, a beam turning rnirror 17,
and a beam focussing mirror 19. Outer duct 7 provides
a housing for annuls region 10. If housing 7 is smaller
in diameter than well 5, an annular region 11 is estab- 30
lished by annular wall 22. In the FIGURE the well 5 is
shown as directed vertically downward through a shale
deposit. However, such a well could also be directed
horizontally through a shale deposit such as through the
face of a cliff. It is not critical or necessary that either 35
duct 6 or 7 be located concentrically within well 5. The
diameter of well 5 is not critical, although the diameter
of central duct 6 should be greater than ten times the
beam diameter. The depth of well 5 is only dependent
upon the depth of the shale deposit or how far into the 40
shale deposit the laser beam is to be directed.
At least one wellbore 20 is drilled into the shale de-
posit for the eventual recovery of gaseous hydrocarbon
products which permeate through fracture zone 2 from
wellbore 5 to wellbore 20. 45
The central duct 6 provides the channel by which the
laser beam can be directed down into the wellbore and
focussed onto the desired portion of the oil shale forma-
tion. Thus, laser beam 13 from laser 15 is reflected by
beam turning mirror 17 down into the central duct 6 of 50
the wellbore. However, beam turning mirror 17 can be
eliminated by placing the laser in a vertical position
above the central core, thereby directing the beam di-
rectly down the central core of the well. The beam is
then reflected at the desired fracture point 4 in the shale 55
formation 3 by a focussing mirror 19 which directs the
focussed laser beam to a spot in the oil shale formation.
It is important that the laser beam strike the side of the
wellbore 5 at an angle so that the slag generated in the
fracture can flow from the fractured zone. The oil shale 60
is rapidly heated by the focussed beam to high tempera-
tures by the action of the focussed beam which causes
fracturing of the region 2 of the shale formation which
initiates combustion in the oil shale formation. The
focussing mirror is placed at the desired level in the well 65
and fixedly attached to duct 7. The reflecting and focus-
sing mirrors are fabricated from uncooled, low absorp-
tion reflecting materials which are compatible with the
high flux beams used. The only important consideration
is that the mirrors be capable of withstanding high flux
densities. The laser beam which is reflected from the
focussing mirror into the shale deposit is focussed to an
extent which is a function of the depth of the well and
the original beam flux density. The beam is directed into
the shale deposit for a time sufficient to cause fracturing
and ignition of a layer of shale.
The first annular region 10 functions as a means for
conducting a pressurized gas into the oil shale forma-
tjon. The gas in addition to supporting combustion and
functioning as a carrier gas for heated shale oil effluent,
^ functions to cool and clean the last focussing mirror
w The gas must ^  capable of supporting combustion
^
 tnerefore is ^  oxygen containing gas such as air or
oxygen. The gas should be relatively dry, i.e., low water
^^
 Tbs gas ^ ^ p^My contain a combustible
component such as methane to aid in the combustion
prOcess, although such a combustible component raises
blems because of ^  possibility of ^  explosion. The
^
 mjected mto ^  we,, «. ^ ^ ^ suffident
fQ ^ ^ combustion ^  the shale J^ from a suitable
^ ^
 fl f urized ^ ^^^^ continuation of combustion is de-
. /. °
__' , . . . . . . . ., , ,
, The focussed laser beam gnerates a hole in the shale
formatl
°
n whosf honzontal depth wuhin the shale is
& TH °* f ^f
. When this point .s reached, the
shale
 fractures preferentially parallel to the bedding
Plane- ™eL mtroductlon of the pressurized gas at the
P°mt of the shale fracture 4 '"PP0*8 a flame front
winch «" ™°ve lblou& the fractured zone in the shale
formation. The laser beam is turned off when the frac-
ture
 extends between the wellbores.
The Saseons hydrocarbon product which is evolved
by the retorting of the shale zone, permeates through
^ fractured shale and is withdrawn through an adja-
cent wel1 2° closed bV a cover 24 and is collected in a
suitable collector 25 and processed for further use. A
vacuum pump 21 can be employed to facilitate removal
^ collection of the evolved gases from an adjacent
well 20 and to direct the flame front selectivity to the
adjacent well 20. Since the gaseous hydrocarbon prod-
uct
 ^
 a
 complex mixture of materials, the manner in
which the gas is subsequently processed is dependent on
what types or blends of hydrocarbon products and
hydrocarbon containing gases are desired. The liquid
hydrocarbon products produced in the process are not
recovered and are allowed to remain in the well.
Having now fully described the invention, it will be
apparent to one of ordinary skill in the art that many
changes and modifications can be made thereto without
departing from the spirit or scope of the invention as set
forth herein.
What is desired as new and intended to be secured by
letters patent is:
1. A method for the in-situ retorting of oil shale and
recovery of gaseous hydrocarbon products, which
comprises:
drilling at least two wellbores into an oil shale forma-
tion underneath the surface of the ground;
fracturing a region of said oil shale formation by
directing a high energy laser beam into one of said
wells and focussing said laser beam onto said re-
gion of said oil shale formation from a laser optical
system;
4,061,190
5 6
forcing a compressed gas into said well through said region of said formation, and wherein said focussed
which said laser beam was directed to the site of beam ignites and fractures said region of said oil forma-
said fracture which supports combustion in the tion.
flame front ignited by said laser beam in the frac- 4. The method of claim 2, wherein a compressed gas
tured region of said oil shale, thereby retorting said 5 ^ forced into said annular region between said housing
oil shale; and • jmd g^j ,juct which gas supports combustion and forces
recovering gaseous hydrocarbon products which ^d flame front ^ gaseous products through said
permeate through said fractured oil shale into the
 fractured region and which simultaneously functions tobore of a well adjacent the well through which said
 dean ^  f^^ j^^
laser beam is directed. . . . . . . . 10 5. The method of claim 1, wherein said compressed2. The method of claim 1, wherein said well is pro- . . *
vided with a housing in which is vertically disposed a "^i1!?1' r °*yf^ , . „ . . . .
central duct having a central core and which provides <-.TJe ^^ of .<=laun *• ***** ""» «>mp«»Bd
an annular region between said housing and said central ** » forced mto "* ^^ corc at a Pressure suffi'
duct and an annular region between said housing and 15 cient to s«PP<>rt combustion,
said
 wej] 7. The method of claim 2, wherein said gaseous hy-
3. The method of claim 2, wherein said laser beam is drocarbon products are recovered.
reflected by a mirror into said central duct such that it *• The method of claim 7, wherein said gaseous hy-
traverses said central duct until it strikes a focussing drocarbon products are recovered by vacuum recovery
mirror located within said central duct at a region 20 through an adjacent well,
within said shale formation which focusses said beam on * * • * *
25
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45
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60
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In-situ laser retorting of oil shale

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