U.S. patent number 3,572,838 [Application Number 04/839,350] was granted by the patent office on 1971-03-30 for recovery of aluminum compounds and oil from oil shale formations.
This patent grant is currently assigned to Shell Oil Company. Invention is credited to Charles C. Templeton.
United States Patent |
3,572,838 |
Templeton |
March 30, 1971 |
RECOVERY OF ALUMINUM COMPOUNDS AND OIL FROM OIL SHALE
FORMATIONS
Abstract
An improved, new and novel method of recovery of oil and
aluminum-containing compounds from subterranean oil shale
formations, by treating such formations with alternating slugs of a
pyrolytically extractive fluid and an aqueous alkaline fluid
containing an acid-insoluble chelating agent and recovering oil and
aluminum compounds from said extractive fluids.
Inventors: |
Templeton; Charles C. (Houston,
TX) |
Assignee: |
Shell Oil Company (New York,
NY)
|
Family
ID: |
25279502 |
Appl.
No.: |
04/839,350 |
Filed: |
July 7, 1969 |
Current U.S.
Class: |
299/4;
166/259 |
Current CPC
Class: |
E21B
43/28 (20130101); E21B 43/247 (20130101); E21B
43/24 (20130101) |
Current International
Class: |
E21B
43/24 (20060101); E21B 43/00 (20060101); E21B
43/16 (20060101); E21B 43/247 (20060101); E21B
43/28 (20060101); E21b 043/28 () |
Field of
Search: |
;299/4,5
;166/259,271 |
References Cited
[Referenced By]
U.S. Patent Documents
Primary Examiner: Purser; Ernest R.
Claims
I claim:
1. In a method of producing shale oil and soluble aluminum
compounds from subterranean dawsonite-containing oil shale
formations comprising the steps of:
a. creating a fractured or rubblized or fragmented oil shale
formation or cavity;
b. flowing into the formation or a cavity pyrolytically extractive
fluid;
c. flowing into the formation or cavity an aqueous liquid
containing a chelating agent in an amount sufficient to dissolve
soluble aluminum compounds;
d. outflowing the liquids produced by steps (a) and (b);
e. separating the aqueous phase from the oil phase and,
f. recovering an aluminum compound from the aqueous phase.
2. The method of claim 1 wherein the in situ combustion for oil
recovery and aqueous liquid dissolution of the dawsonite is
sequentially repeated and the aqueous liquid is an aqueous alkaline
liquid containing a sodium salt of a alkylene polyamine
polycarboxylic acid.
3. The method of claim 1 wherein the aluminum compound is recovered
from dissolved dawsonite.
4. The method of claim 3 wherein the oil shale is pyrolyzed by
injecting therein an in situ combustible material at an elevated
temperature sufficient to effect oil extraction and the chelating
agent in the aqueous fluid is an alkali metal salt of an amino
carboxylic acid.
5. The method of claim 4 wherein the aqueous alkaline liquid is an
aqueous alkaline solution containing tetra sodium ethylene diamine
tetracetate.
6. The method of claim 4 wherein the fluid is recovered by
combustion treatment is shale oil and the aqueous liquid containing
a chelating agent used to dissolve the dawsonite is an aqueous
alkaline liquid containing an acid insoluble chelating agent.
7. The method of claim 6 wherein the combustion mixture is
maintained as a foamed mixture of air and water.
Description
BACKGROUND OF THE INVENTION
1. Field of the Invention
This invention is directed to a new, novel and improved method for
recovering shale oil and aluminum-containing compounds from
subterranean oil shale formations containing both products by
sequential treatment of fracture-permeated zones, such as fractured
or rubblized zones and/or fragmented portions of such subterranean
formations produced by suitable fracturing and/or solids extracting
means, to a controlled pyrolytic extractive process in order to
produce organic fluidizable materials such as hydrocarbons and oil
and also recovering aqueous soluble minerals such as soluble
aluminum-containing compounds, e.g., dawsonite or other soluble
minerals capable of forming chelates, when contacted with an
aqueous alkaline fluid containing an acid insoluble chelating
agent. The recoverable products can be separated from an outflowing
fluid by a number of suitable means which will be fully described
below.
The use of various explosive techniques both nuclear and nonnuclear
to fracture, rubblize or break up or fragment underground oil shale
formations so as to form a fractured formation or a chimney or a
cavern filled with rubble or fragmented oil shale to facilitate
shale oil recovery from such fractured, fragmented or rubblized
areas by in situ pyrolysis is well known in the art. Although some
oil shale formations under discussion are known to also contain
dawsonite and/or other soluble aluminum compounds, their recovery
in conjunction with in situ pyrolysis of shale oil recovery, or per
se, has not been thought feasible in the past because of the
thermally enhanced formation of insoluble oxides and/or silica
complexes of aluminum. Such conversions of dawsonite (sodium
aluminum basic carbonate) or other soluble aluminum compounds,
cause the recovery thereof to become relatively costly and
unattractive. Therefore, attempts to recover dawsonite from
subterranean oil shale formations has not been attempted except
with respect to shallow deposits from which the mineral is mined
and processed in surface locations and a valuable source of
aluminum and aluminum products has been essentially neglected.
A number of proposals have been made in the art to recover
dawsonite from oil shale above ground such as described in U.S.
Pat. No. 3,389,975 which is directed to subjecting an oil shale
previously retorted above ground to a leaching process using an
aqueous solution of sodium carbonate and sodium hydroxide and
subsequently precipitating the dawsonite with carbon dioxide in
order to recover dawsonite. In copending Ser. No. 769,909, filed
Oct. 23, 1968, and now U.S. Pat. No. 3,502,372 in situ recovery of
oil and dawsonite from subterranean rubblized oil shale formation
is described using a combination of a pyrolysis and solution mining
technique involving forming a fracture-permeated zone within a
subterranean oil shale formation, prior to such treatment.
The above-ground retorting techniques described above for
recovering oil and dawsonite are outside the scope of the present
invention, and are undesirable and unsuitable for carrying out the
process of the present invention since the process results in the
formation of large amounts of insoluble materials which are
undesirable and difficult to handle making these operations costly
and unattractive. The process described in the copending
application is often more effective and less costly than an
above-ground retorting technique but tends to cause a formation of
some insoluble products and a failure to recover a significant
proportion of the soluble aluminum compounds.
Throughout the specification the term "shale oil" refers to one or
more of the liquid or gaseous hydrocarbons and/or substituted
hydrocarbons resulting from pyrolysis and/or solvent extraction of
the kerogen components of an oil shale formation. Similarly, the
term "pyrolytically extractive fluid" refers to a hot fluid that
initiates or accelerates the pyrolysis of kerogen and entrains or
displaces shale oil. Examples of pyrolytically extractive fluids
include the products of an in situ combustion within the oil shale
formation; individual or mixed hydrocarbons, such as methane,
benzene, etc.; steam or aqueous liquid; mixtures of such fluids
with reactive components, such as an acid, a phenol, etc. In a
shale oil recovery operation, such fluids are heated so that they
have an in situ temperature sufficient to provide a relatively
rapid rate of kerogen decomposition, such as a temperature of at
least about 500.degree. F.
2. Objects of the Invention
It is an object of the invention to recover aluminum-containing
compounds and oil from underground oil shale formations.
It is an object of this invention to recover from subterranean oil
shale formations containing aluminum compounds such as dawsonite
both the oil and the aluminum compounds by means of pyrolytically
extractive fluid and aqueous alkaline fluids containing chelating
agents.
It is still another object of this invention to recover oil and
dawsonite from subterranean fractured, rubblized or fragmented oil
shale formations by circulating through said fractured or rubblized
zones alternating slugs of a pyrolytically extractive fluid and an
aqueous alkaline fluid containing a chelating agent and recovering
oil and dawsonite from the outflowing fluid.
Other objects of this invention will be apparent from the following
description.
SUMMARY OF THE INVENTION
The present invention is directed to recovery of shale oil and
soluble aluminum compounds such as dawsonite from a subterranean or
underground dawsonite containing oil shale formations by fracturing
and/or rubblizing said formation so as to form a permeable zone
therein and circulating therethrough alternating slugs of a
pyrolytically extractive fluid and an aqueous alkaline fluid
containing an effective amount, sufficient to prevent insoluble
product formation, of an acid-insoluble chelating agent and
thereafter recovering and processing the outflowing fluid so as to
effect recovery of the oil-phase from the aqueous-phase and
separately processing the oil-phase to recover oil therefrom and
aluminum compounds, e.g., dawsonite and the chelating agent, from
the water-phase components. In certain instances, depending upon
the properties of the oil shale formation being treated and/or the
pyrolytically extractive fluid being used, additional portions of
aqueous-fluid-solubilized shale oil can be recovered from the
water-phase components of the outflowing fluid.
Subterranean oil shale formations that contain water-soluble
aluminum compounds can be located by various known exploration
techniques. Fracture-permeated zones can be formed within such
formations by detonating one or more nuclear or nonnuclear
explosive devices within the borehole of one or more wells, by
mining portions of the oil shale to leave tunnels which can be
collapsed to form a fracture-permeated zone, or by various
combinations of hydraulic fracturing, solution mining, acidizing,
and the like techniques. Fluids can be circulated through such
fracture-permeated zones by opening the borehole of at least one
well into fluid communication with at least two separated regions
within the zone, inflowing fluid by pumping it into at least one
well conduit in fluid communication with one region within the zone
and outflowing fluid by pumping it from at least one well conduit
in fluid communication with another region within the zone. If
desired, the fluid circulation can be accomplished through a single
well that communicates with a single region within a
fracture-permeated zone, by inflowing fluid against the back
pressure created by the injection of the fluid and outflowing the
fluid by reducing the pressure within the well and allowing the
fluid to return in response to the pressure within the subterranean
region.
The oil-shale-pyrolyzing fluid can comprise the combustion products
of substantially any type of in situ combustion in which the
combustion-supporting fluid is sufficiently free of alkaline
material to form nonalkaline combustion products, hot hydrocarbons
such as benzene, volatile compounds of oil shale, steam or hot
aqueous nonalkaline fluids, phenolic materials, mixtures of
hydrocarbons with phenols, polyacids or the like, etc.
The chelating agents useful as additives in the aqueous alkaline
fluid of this invention can include any organic chelating agent
capable of chelating with the aluminum or other prevalent metallic
compounds present in the oil shale and forming soluble compounds in
the aqueous solution and include nitrogen-containing carboxylic
acids and amine or metallic salts thereof such as amino-, imino-,
nutrilo-, carboxylic acids and salts thereof such as described in
U.S. Pats. No. 2,631,978; No. 2,959,547; No. 3,256,196 and No.
3,409,551 and include amino carboxylic acids, e.g., ethylene
diamine tetracetic acid and salts thereof, methyl iminodiacetic
acid, nitroacetic acid, phenyl iminodiacetic acid of which
preferred are the amine and alkali metal (sodium) salts of ethylene
diamine tetracetic acid, e.g., di-, tri- and tetrasodium ethylene
diamine tetracetic (Na.sub.2.sub.-, Na.sub.3.sub.-, or Na.sub.4
EDTA) and mixtures thereof.
In the present invention, the presence of the chelating agent in
the aqueous alkaline solutions inhibits and/or alleviates the
effects of the conversion of aqueous-fluid soluble aluminum
compounds, such as dawsonite, to substantially insoluble aluminum
compounds, such as analcite. Particularly in oil shale formations
at relatively shallow depths, both forms of aluminum compounds may
be present in the natural formation. When a hot aqueous alkaline
solution is being circulated through a fracture-permeated zone of
an oil shale formation that contains a soluble aluminum compound, a
conversion to an insoluble compound such as analcite may occur
during the contact between the hot alkaline solution and the oil
shale. When the hot alkaline solution contains a chelating agent,
the aluminum is held in solution in the form of an
aluminum-chelating-agent complex and the formation of insoluble
aluminum silicate compounds is inhibited. The formation of
insoluble aluminum silicate compounds is also retarded by the
presence of calcium ions in such hot alkaline solutions, since the
calcium ions tend to combine with the silicate to form insoluble
calcium silicate compounds to such as extent that the aluminum
remains in solution. Particularly, in respect to chelating agents,
such as an aminopolycarboxylic acid chelating agent, aluminum is
held more tightly than is calcium in complexes with the chelating
agent; and, thus, the beneficial effects of the presence of calcium
ions and chelating agent in a hot alkaline solution are at least
supplementary. Hot alkaline solutions containing both the chelating
agent and calcium ions tend to inhibit the conversion of soluble
aluminum compounds to insoluble aluminum silicate compounds and
also enhance the rate at which naturally occurring insoluble
aluminum silicate compounds, such as analcite, are digested and
converted to dissolved, soluble aluminum-chelating-agent complexes
and precipitated, insoluble calcium silicate compounds.
DESCRIPTION OF THE DRAWINGS
The FIGURE is an illustration of a preferred embodiment of this
invention wherein 30 is the oil shale formation of which zone 31 is
fractured and fragmented and from which oil and dawsonite is to be
recovered. The formation is penetrated by an injection well 32 and
a production well 33 each of which have tubing strings 34 and 35,
respectively, in which through tubing string 34 is alternatively
injected a pyrolytic extracting fluid from 36 and an alkaline
aqueous alkaline fluid containing a chelating agent from vessel 37.
The injection via tubing string 34 of fluids 36 and 37 is
alternatively carried out as required to effect oil pyrolysis and
dawsonite solubilization to be recovered as outflowing fluids via
well 33 through tubing string 35. At the surface the outflowing
fluid from 35 is processed for separation by flowing into separator
38 via lines 39a and 39b between which is a surface processing unit
39 and the oil phase is separated in 38 and directed via line 40 to
vessel 41. The aqueous phase is directed to through line 42 into
vessel 43 where it is acidified in line 44 and the chelating agent
precipitated in vessel 45 separated and returned to vessel 37 via
line 46. The pH adjusted aqueous solution of dawsonite is directed
via line 47 into vessel 48 where the solution is treated with a
base and on precipitation the precipitated aluminum oxide product
is recovered in vessel 49 and the aqueous waste discarded via line
50.
SPECIFIC EMBODIMENT OF THE INVENTION
In a preferred process for conducting the present invention the
pyrolytically extractive fluid is formed in situ by initiating an
underground combustion within the fracture-permeated zone in the
oil shale formation and injecting a combustion-supporting fluid to
produce a pyrolytically extractive fluid resulting from the
products of combustion. The combustion-supporting fluid may contain
components, such as an aqueous liquid, to control the temperature
and heat-transport properties of the combustion, foam to control
the sweep efficiency of fluids moving through interstices within
the fracture-permeated zone, fuel to supplement that available in
the exposed oil shale surfaces, etc.
In the preferred process, a slug of an aqueous alkaline solution
containing a chelating agent is preferably injected prior to the
initiation of the underground combustion such as an
amino-carboxylic acid, e.g., ethylene diamine tetra acetic acid
(EDTA) and salts thereof (e.g., Na.sub.4.sub.- EDTA) via vessel 37
is shown in the FIGURE. The inflowing aqueous solution is heated,
preferably by means of surface-located or borehole-located heating
device, so that it preheats the oil shale to a temperature
approaching the ignition temperature of the oil shale. Such a
process of preheating an oil shale for an in situ combustion is
described in greater detail in the copending patent application of
J. A. Herce et al. Ser. No. 767,174, filed Oct. 14, 1968 and is
directed to a process for producing shale oil from a subterranean
oil shale formation by controlled in situ combustion in a cavern
that contains a mass of fracture-permeated oil shale. The oil shale
fragments are preheated with an aqueous liquid to cause a reduction
in their particle size and improve the distribution of
permeabilities and surface area-to-volume ratios within the cavern
prior to the initiation of underground combustion.
Such an aqueous-fluid preheating is particularly advantageous in
that it induces the exfoliation of portions of the
fracture-permeated oil shale into small pieces and thus improves
both the distribution of effective permeabilities within the
interstices between the pieces of oil shale and the ratio of
surface area of the oil shale pieces to the volume of the oil shale
pieces.
In general, in the present process, each slug of aqueous alkaline
solution containing a chelating agent, e.g., Na.sub.4 EDTA, should
have a volume at least exceeding the solid-free void space of both
the fracture-permeated zone within the oil shale formation and the
inflow and outflow conduits. If desired, the outflowing portions of
a relatively small size slug can be reheated and recycled through
the fracture-permeated zone. Where the fracture-permeated portion
of the oil shale has not been preheated, the inflowing portions of
the chelating-agent solution are preferably heated, continuously or
incrementally, to increasingly higher temperatures which are
significantly greater than the normal temperature of the oil shale
formation. The pressure of the inflowing chelating-agent solution
is preferably increased, by maintaining a back pressure on
outflowing portions, if necessary, to the extent/required to
maintain substantially all of the solution in the liquid phase.
When the chelating-agent solution is being injected prior to the
initiation of an underground combustion, the injecting and heating
are preferably conducted so that, at least near the point of inflow
into the fracture-permeated zone of oil shale, the oil shale is
heated to a temperature of at least several hundred degrees F. for
a period of at least several days, with temperature of at least
about 400.degree. F and times of at least one week being preferred.
In general, the alternations of slugs of chelating-agent solution
and pyrolytically extractive fluid are preferably repeated by
interrupting the circulation of the pyrolytically extractive fluid
(e.g., by maintaining an underground combustion), initiating
circulation of chelating-agent solution, interrupting the
circulation of chelating-agent solution, reinitiating the
circulation of pyrolytically extractive fluid, etc. Where the
regional tectonics and/or the well assembly equipment make it
undesirable to inflow an aqueous fluid at a pressure sufficient to
keep it substantially liquid at the temperatures created by a
pyrolytic extraction, e.g., those created by an underground
combustion, the inflowing of the chelating-agent solution is
preferably preceded by the inflowing of a slug of water that is
softened to an extent preventing scaling at the temperature
existing within the fracture-permeated zone. The time and volume of
such a water circulation are preferably adjusted to lower the
temperature, at least near the point of inflow into the oil shale,
to a temperature at which inflowing portions of a chelating-agent
solution can be kept substantially liquid under pressures which are
desirable for employment.
ILLUSTRATED EMBODIMENT OF THE PRESENT INVENTION
After a rubblized or fractured subterranean oil shale formation has
been subjected to a dry in situ combustion, an aqueous solution
containing an alkaline agent such as NaOH or Na.sub.2 CO.sub.3 and
a chelating agent such as an alkali metal salt of ethylene diamine
tetra acetic acid, e.g., Na.sub.4 EDTA (the sodium salt of
ethylenediaminetetraacetic acid) is injected through a well into
the partly cooled recovery zone of the shale formation at a
temperature of from about 200.degree. to about 225.degree. C, with
the aluminum remaining soluble as a mixture of Al-EDTA and
aluminate ion Al0.sub.2.sup..sup.-. The solution returning from a
production well to the surface containing some EDTA is in the form
of metal complexes (Al-EDTA.sup.-, Ca-EDTA.sup.-.sup.2, or
Mg-EDTA.sup.-.sup.2, expected from leaching spent oil shale), since
the metal-EDTA form is more stable at higher temperatures than the
free EDTA. The produced solution is cooled in a heat exchange
scheme to less than 100.degree. C. to recover the EDTA as
precipitated H.sub.4 EDTA by acidifying the produced solution with
an acid such as hydrochloric acid or sulfuric acid to a pH of about
1.6. The solid H.sub.4 EDTA is separated from the solution by
either filtration or decantation, the solution is then alkalized by
NaHCO.sub.3 or NaCO.sub.3, or a mixture of both, so that a pH of
6.5 to 7.5 the Al(OH).sub.3.sup..xH.sub.2 O when filtered off may
contain enough impurities to warrant its solution in acid, and a
second alkalization with Na.sub.2 CO.sub.3 to obtain high purity
Al(OH).sub.3.sup.. xH.sub.2 O. Finally, the Al(OH).sub.3.sup..
xH.sub.2 O is again filtered off, and calcined to Al.sub.2 O.sub.3.
Such ALSO.sub.3 can then be sent to conventional electrolytic
plants for production of aluminum metal.
The separated H.sub.3EDTA is dissolved in a NaOH solution, which
can be blended with fresh natural brine, to form an aqueous phase
suitable to be sent to the injection wells.
* * * * *