U.S. patent number 3,695,354 [Application Number 05/023,549] was granted by the patent office on 1972-10-03 for halogenating extraction of oil from oil shale.
Invention is credited to Richard L. Dilgren, Gary Drinkard.
United States Patent |
3,695,354 |
Dilgren , et al. |
October 3, 1972 |
HALOGENATING EXTRACTION OF OIL FROM OIL SHALE
Abstract
A process for recovering oil by circulating hot fluid through a
permeable mass of oil shale is improved by circulating hot fluid
that contains a halogenated organic compound.
Inventors: |
Dilgren; Richard L. (Houston,
TX), Drinkard; Gary (Houston, TX) |
Family
ID: |
21815781 |
Appl.
No.: |
05/023,549 |
Filed: |
March 30, 1970 |
Current U.S.
Class: |
166/272.4;
166/266; 166/267; 208/390 |
Current CPC
Class: |
E21B
43/40 (20130101); C09K 8/592 (20130101); E21B
43/24 (20130101) |
Current International
Class: |
E21B
43/24 (20060101); E21B 43/34 (20060101); E21B
43/16 (20060101); E21B 43/40 (20060101); C09K
8/592 (20060101); C09K 8/58 (20060101); E21b
043/24 (); C10g 001/04 () |
Field of
Search: |
;166/272,271,275,303,302,256,259,260,261,267,266 ;208/11 |
References Cited
[Referenced By]
U.S. Patent Documents
Primary Examiner: Novosad; Stephen J.
Claims
What is claimed is:
1. In a process for producing shale oil by circulating steam
through a permeable mass of oil shale, the improvement which
comprises circulating with said steam through said oil shale mass
an effective amount of at least one halogenated organic
compound.
2. The process of claim 1 wherein the halogenated compound is
dichlorobutane.
3. The process of claim 1 wherein the halogenated compound is
trichloropropane.
4. The process of claim 1 wherein the halogenated compound is
dichlorodiethyl ether.
5. The process of claim 1 wherein the halogenated organic compound
is a sodium trichloroacetate aqueous solution.
Description
BACKGROUND OF THE INVENTION
This invention relates to producing shale oil or other organic
material from oil shale. It is particularly useful in producing
shale oil from a subterranean oil shale.
Prior shale oil production processes have utilized a circulation of
a hot fluid through a permeable mass of oil shale. It causes the
kerogen or other organic components of the oil shale to be
thermally converted, by pyrolysis or retorting, to fluids or
solutes which are dissolved or entrained in the circulating hot
fluid. In treating a subterranean oil shale, the circulating fluid
is pumped through conduits in well boreholes leading to and from a
permeable region within the oil shale and the produced shale oil is
recovered from the outflowing fluid. The circulated fluid may be
heated at a surface location or in the well borehole before it
contacts the oil shale or may be heated within the oil shale by
means of an in situ combustion.
The cost of operating a hot fluid circulating shale oil production
process tends to be undesirably high relative to the value of the
product. A significant factor in the cost of the operation is the
relatively slow rate at which the oil shale can be heated by the
circulating hot fluid. A primary object of the present invention is
to provide a shale oil production process in which the rate of
thermal fluidization and recovery of the organic components is
increased by the action of a hot, reactive/extractive, fluid which
tends to supplement a thermal conversion by a chemical reaction
and/or dissolution that accelerates the rate of the fluidization
and recovery.
SUMMARY OF THE INVENTION
In accordance with this invention, organic materials are recovered
from an oil shale by circulating hot fluid containing a halogenated
organic compound through a permeable portion of the oil shale and
recovering organic materials from the circulated fluid. The organic
materials which are produced by this invention comprise the
components of a conventional shale oil supplemented and/or modified
by the presence of halogenated and/or depolymerized derivatives of
the relatively high molecular weight pyrolysis products of kerogen
and/or bitumen. The present invention is particularly useful where
a hot fluid is circulated through a permeable portion of a
subterranean oil shale.
The halogenated organic compounds which are used in the present
invention can be substantially any which are fluidizable and
reactive with kerogen at a temperature applicable to a fluid which
is circulating within a permeable portion of oil shale. The
halogenated organic compound should be fluidizable in the sense of
being a fluid or being soluble in a fluid at such a temperature.
The fluid circulated within the oil shale can consist of
substantially pure halogenated organic compound or a mixture of at
least one such compound with at least one other material. Examples
of halogenated organic compounds suitable for use in this invention
comprise organic materials such as hydrocarbons or substituted
hydrocarbons which have been halogenated with a reactive halogen
such as chlorine, bromine or iodine. The chlorinated organic
compounds are preferred, and the polyfunctional chlorinated organic
compounds are particularly suitable. Examples of suitable compounds
include the chlorides, bromides or iodides of hydrocarbons
containing from about one to eight carbon atoms; the polyfunctional
analogs of such compounds, such as dichlorobutane,
trichloropropane, dichlorodiethyl ether, methylchloroform, a
solution of a soluble salt of trichloroacetic acid, etc.
While the present invention is not premised on any particular
reaction mechanism, the following may be involved in the materially
enhanced rate of organic material recovery that is exhibited by the
present process. At a temperature of at least a few hundred degrees
Fahrenheit, the molecules of kerogen or bitumen contain, or behave
as though they contain, hydrogen atoms which tend to be active. The
molecules containing such active hydrogen atoms react with
molecules of a halogenated organic compound to form a hydrogen
halide. Such hydrogen halides are strong inorganic acids which tend
to enhance the chemical conversion or solution of inorganic
components of the oil shale. Such a solution or conversion of
inorganic solids creates additional permeability and speeds up the
heating and dissolution of the organic components. The produced
hydrogen halides also tend to induce a depolymerization of long
chain kerogen or bitumen molecules or their pyrolysis products and
such depolymerization products tend to be more soluble or more
volatile (and thus more rapidly fluidized) than the untreated
portions of kerogen or bitumen or their pyrolyzates.
The present invention is particularly useful in producing shale oil
from a subterranean oil shale that contains water-soluble minerals
and/or heat-sensitive carbonate minerals. The presence of such
minerals tends to enhance the rate of growth of a permeable zone
due to the fluidization of inorganic components of the oil shale.
The heat-sensitive carbonates are fluidized by both a thermal
conversion to carbon dioxide and water, and a dissolution of
water-soluble unreacted portions or conversion products. The
hydrogen halides produced by the reaction of the halogenated
organic compound used in the present invention are effective in
enhancing the rate of such fluidizations of the inorganic
components of the oil shale.
In situations in which it is desirable to mine portions of an oil
shale formation and pyrolyze the mined oil shale in a fluid-heated,
pressure-tight, surface located retort, the pyrolytic recovery of
petroleum material is improved by incorporating an effective amount
of halogenated organic compound in the hot fluid that is circulated
through the oil shale. In such a process, chunks or fragments of
the oil shale are preferably contacted with a hot aqueous and/or
hydrocarbon fluid that contains at least about 2 percent by weight
of at least one halogenated organic compound at a temperature of at
least about 500.degree. F under a pressure sufficient to keep a
significant proportion of the fluid in the liquid phase. Where the
oil-shale-contacting fluid predominates in hydrocarbon components,
e.g., a benzene solution of a halogenated organic compound, the oil
shale is preferably preheated by contacting it with hot aqueous
liquid. The contacting of chunks of oil shale with a hot aqueous
liquid (i.e., with hot water utilized in preheating the oil shale
and/or a hot aqueous solution containing at least one halogenated
organic compound) tends to exfoliate the pieces of the oil shale.
The exfoliation reduces the tendency for clinkers to be formed
during the pyrolysis-extraction operation and reduces the extent to
which the oil shale needs to be crushed in order to obtain an
efficient recovery of petroleum material.
BRIEF DESCRIPTION OF THE DRAWING
FIG. 1 is a vertical sectional view of an oil shale formation to
which the recovery process of this invention is applied through a
single well;
FIG. 2 is a vertical sectional view of the oil shale formation of
FIG. 1 in which a pair of wells are used in the invention; and
FIG. 3 is a vertical sectional view of an alternate arrangement for
using the invention with a single well.
DESCRIPTION OF THE PREFERRED EMBODIMENT(S)
Referring to the drawing, FIG. 1 shows a well borehole 11 extending
into subterranean oil shale formation 12. Fluid communication may
be established between points 13 and 14 in oil shale formation 12
and adjacent to borehole 11 along vertical fractures by, for
example, a conventional hydraulic fracturing procedure. A hot fluid
containing a halogenated organic compound is flowed through tubing
17 past packer 19. The fluid passes through perforations 20 and 21
in casing 22 and returns to the surface through the annular opening
around tubing 17. The entrained fluidized shale oil material is
recovered from the outflowing portions of the circulating fluid by
procedures such as known phase separation and/or distillation
procedures. Although a single well may be used, it is generally
preferred to use at least a pair of wells.
As shown in FIG. 2, a pair of wellbores 23 and 24 extend into
subterranean oil shale formation 25. Fluid communication is
established between point 26 adjacent to wellbore 23 and point 27
adjacent to wellbore 24. In a preferred embodiment, the depths of
such points may be those at which a tuffaceous streak is
encountered by a pair of well boreholes between which the streak is
continuous. The permeable channel extending through the oil shale
may be formed by the process of locating and acidizing a tuffaceous
streak as described in U. S. Pat. No. 3,481,398. At least one hot
halogenated organic compound,or a fluid containing such a compound,
is flowed through tubing 29 past packer 30. The fluid passes
through perforation 31 in the casing 32 of wellbore 23, through
points 26 and 27, and through perforation 33 in the casing 34 of
wellbore 24. Fluidized materials derived from the oil shale are
recovered from the circulated fluid.
In FIG. 3 the permeable zone formed within oil shale formation 12
is preferably a relatively voluminous permeable fragmented zone 35.
The term "permeable fragmented zone" refers to a multiply fractured
zone in which the volume of the interconnected openings within the
fractures provide a void volume of from about 5 to 40 percent of
the volume of the zone.
Permeable fragmented zones can be formed by known hydraulic and/or
explosive techniques for fracturing subsurface earth formations.
Suitable techniques are described in U. S. Pats. Nos. 1,422,204 and
3,481,398. The streak acidizing procedure of the latter patent may
be used to form a channel into which a liquid explosive is injected
and subsequently detonated, in order to form a generally
disc-shaped permeable fragmented zone. High-power explosives, such
as those produced by nuclear devices, are particularly suitable
means for forming such fragmented zones. In general, the permeable
fragmented zone formed by a nuclear device has a vertically
extensive and generally cylindrical shape.
In circulating hot fluid through a permeable fragmented zone, the
flow paths can be vertical or horizontal and can involve a radially
expanding or line-drive type of displacement of the fluid within
the oil shale. Generally, a substantially vertical downward flow is
preferred.
In FIG. 3, zone 35 may comprise a nuclear chimney type of permeable
fragmented zone. In treating such a zone, one or more wells 36 are
drilled to near the bottom, preferably while the zone is hot, or at
least warm, from the explosion energy. In the illustrated
arrangement of FIG. 3, the well 36 is drilled and cased to near the
bottom and the casing 37 is perforated at 38 and 39 and equipped
for injecting fluid through the borehole annulus above packer 18,
and through perforations 38 into the upper portion of the
fragmented zone. Fluid is produced from near the bottom of the zone
through perforations 39 and tubing string 40. The adjustment of the
pressure within the permeable fragmented zone to one selected for
the circulation of heated fluid is effected by controlling the rate
of withdrawing fluid from the cavern relative to the rate of
injecting fluid into the cavern.
As indicated in FIGS. 1 through 3, equipment and techniques, such
as a conventional arrangement of a heater 41, pump 41a, separator
42, and heat exchanger 43 may be used for pressurizing, heating,
injecting, producing, and separating components of the fluid that
is circulated through the permeable zone 35. The production of the
fluid can be aided by down-hole pumping means, not shown, or
restricted to the extent necessary to maintain the selected
pressure within the zone. The pressure in the zone is preferably
maintained at a level suited for economically transferring heat
into the zone by circulating a fluid that is economically available
at the well site.
In certain situations, it is advantageous to circulate a hot fluid
containing a mixture of relatively low molecular weight,
predominantly aromatic hydrocarbons having relatively low critical
temperatures and pressures. With such hydrocarbons (which may
include significant proportions of shale oil hydrocarbons) the
temperatures and pressures within the permeable zone may provide
conditions approaching or exceeding the critical conditions for
part or all of the circulating hydrocarbons. In the critical or
super-critical region, such hydrocarbons have densities and
viscosities that are intermediate between their gas and liquid
states and are particularly effective in extracting organic
components from oil shale.
In a preferred procedure, the hot fluid that contains the
halogenated organic compound is (or contains) steam and is
circulated through the permeable oil shale formation under
conditions such that at least most of the steam is condensed within
the oil shale. The proportion of the halogenated organic compound
is preferably from about 2 to 10 percent by weight of the
circulating fluid. The circulating fluid may contain the
halogenated organic compound either as a solute and/or a separate
fluid phase that is introduced either continuously or
intermittently.
Comparative tests have been conducted with respect to the rates at
which organic materials are removed from a permeable mass of oil
shale through which hot fluids of various types are circulated.
Such experiments have indicated that where the circulating hot
fluids were, respectively, dichlorobutane, trichloropropane,
dichlorodiethyl ether, and mixtures of such materials with,
respectively, aromatic and aliphatic solvents for oil shale
hydrocarbons, the time periods required to reduce the organic
content of the oil shale to one-half of its original value (due to
the circulation of the hot fluid) were significantly less than the
times required where the circulating hot fluid was such a solvent
free of the halogenated organic compound.
Similar improvements in the rates at which organic materials were
removed were observed when the circulated fluid was a steam
containing from about 2 to 10 percent by weight of at least one of
the halogenated organic compounds mentioned above and the rates due
to circulating steam containing a halogenated organic compound were
compared with those due to steam free of those compounds.
In the tests of both of the types mentioned above, it was apparent
that any halogenated organic compound in the gas phase tended to be
selectively absorbed into the organic components of the oil shale
to an extent tending to cause cracking or fracturing along the
bedding planes of the oil shale. In addition, it was apparent that
the rates and extents to which rubbling occurred within the oil
shale material was enhanced by the presence of the halogenated
organic compound.
* * * * *