U.S. patent application number 11/216238 was filed with the patent office on 2006-03-02 for method for high temperature steam.
Invention is credited to William C. Pfefferle.
Application Number | 20060042794 11/216238 |
Document ID | / |
Family ID | 37968283 |
Filed Date | 2006-03-02 |
United States Patent
Application |
20060042794 |
Kind Code |
A1 |
Pfefferle; William C. |
March 2, 2006 |
Method for high temperature steam
Abstract
A method for the recovery of upgraded oil from an oil-bearing
formation is provided wherein a hot gas phase fluid comprising
steam is brought into contact with a heavy oil reservoir, such as
by injection, and the hot fluid heats at least a portion of the
reservoir to a temperature high enough for steam cracking, and
subsequently the steam is reacted with the heavy oil to produce
steam cracked lighter oil.
Inventors: |
Pfefferle; William C.;
(Madison, CT) |
Correspondence
Address: |
Robert L. Rispoli;Precision Combustion, Inc.
410 Sackett Point Road
North Haven
CT
06473
US
|
Family ID: |
37968283 |
Appl. No.: |
11/216238 |
Filed: |
August 30, 2005 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
60606755 |
Sep 1, 2004 |
|
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60606756 |
Sep 1, 2004 |
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Current U.S.
Class: |
166/272.7 |
Current CPC
Class: |
E21B 43/24 20130101 |
Class at
Publication: |
166/272.7 |
International
Class: |
E21B 43/24 20060101
E21B043/24 |
Claims
1. A method of recovery of upgraded oil from an oil-bearing
formation comprising: a) providing a hot gas phase fluid comprising
steam; b) bringing the fluid into contact with a heavy oil
reservoir; c) heating at least a portion of the reservoir to a
temperature high enough for steam cracking; and d) reacting the
steam with heavy oil to produce steam cracked lighter oil.
2. The method of claim 1 wherein the hot fluid comprises steam
produced by a conventional steam flood boiler that is mixed with
sufficient oxygen to heat the reservoir to a temperature adequate
for steam cracking of oil on combustion.
3. The method of claim 1 wherein the hot fluid comprises an
admixture of products of downhole combustion and steam.
4. The method of claim 1 including the additional step of
withdrawing cracked oil through a production well.
5. The method of claim 4 wherein the production well is the
injection well.
6. The method of claim 4 wherein the oil is withdrawn through a
horizontal well.
7. The method of claim 1 wherein methane and carbon dioxide are
produced in addition to steam cracked lighter oil.
8. The method of claim 2 wherein said temperature is greater than
900 degrees Fahrenheit.
9. The method of claim 1 wherein the hot fluid comprises a
catalyst.
10. The method of claim 9 wherein the catalyst comprises boria.
11. The method of claim 9 wherein the catalyst comprises a
potassium compound.
12. The method of claim 9 wherein the catalyst comprises a
catalytic metal salt.
13. The method of claim 7 wherein at least a portion of the methane
produced is combusted to produce steam.
14. The method of claim 1 wherein the step of bringing the fluid
into contact with a heavy oil reservoir comprises injection of the
fluid through an injection well.
15. The method of claim 14 wherein fluid injection is stopped and
oil is subsequently withdrawn through the injection well.
16. The method of claim 14 wherein the injection well comprises a
horizontal configuration.
Description
CROSS-REFERENCE TO RELATED APPLICATION
[0001] This application claims the benefit of U.S. Provisional
Application No. 60/606,755 filed Sep. 1, 2004, and U.S. Provisional
Application No. 60/606,756 filed Sep. 1, 2004.
BACKGROUND
[0002] 1. Field of the Invention
[0003] This invention provides a novel concept for the mobility
enhancement of heavy crude oil, thus making possible more efficient
and effective recovery of oils including oils that are presently
accessible using existing techniques. Such oils include not only
the balance of the oil left after primary and secondary recovery
operations, but heavy oils and bitumen such as found in Athabaskan
oil sands. More particularly, the present invention provides a
downhole crude oil processing method that improves reservoir sweep
efficiency and enhances quality of the crude oil delivered to the
surface. In addition, coke formed may be recovered in the form of
natural gas. Cost per barrel is consequently reduced. The method of
the present invention significantly increases available domestic
oil reserves, and consequently decreases dependence on oil imports
by making oil available from the abundant deposits of otherwise
in-accessible heavy oils.
[0004] 2. Description of the Related Art
[0005] The industrial world depends heavily on petroleum for
energy. However, it has been increasingly clear that production
cannot keep up with the rapidly growing need, particularly in view
of the growing demand from countries such as China and India.
Moreover, the bulk of new production must come from the politically
unstable Middle East. Fortunately, it is feasible to produce crude
oil from unconventional deposits such as heavy oils and bitumen
which represent a resource much greater than conventional
petroleum. Such deposits may be recovered by mining and upgrading
the recovered oil. However, by far the bulk of such heavy oil
reserves occur at depths greater than that from which it can be
recovered by surfaces mining. Thus steam flooding extraction
methods such as SAGD (steam assisted gravity drainage) have proven
useful.
[0006] Steam flooding from surface steam generators is an effective
and broadly applicable thermal recovery approach to enhanced oil
recovery. The primary effects are heating the oil to an elevated
temperature thereby reducing the oil viscosity sufficiently low
enough to allow flow and displacing the oil toward a production
wellhead. The oil removed tends to be the more mobile fraction of
the reservoir, and the combustion emissions of the steam generator
can be limiting (as in California). Such steam flooding faces
limiting technical and economic obstacles relating to conductive
heat losses through the wellbore and incomplete reservoir sweep
efficiency, especially in heterogeneous reservoirs. With a large
fraction of heavy oils there is a further problem: even if the
heavy oil is heated sufficiently to promote flow to a wellhead,
heat loss in flowing to the surface from typical reservoir depths
will result in some loss of fluidity of the heavy oil before
reaching the surface. In addition, the oil produced cannot be
transported by pipeline without dilution with a lighter oil.
Further, although surface mining can recover close to 100 percent
of the oil in place, steam flooding typically can recover as little
as fifty percent of the oil in place. The oil recovered must be
upgraded, typically by coking. However, because thermal coking
produces a low-grade oil, there is a trend towards hydrogenation
and hydrocracking thus producing a synthetic crude oil similar to a
high quality conventional light crude. This requires a supply of
hydrogen. Capital costs are high and the availability of natural
gas to produce the needed hydrogen can be an issue.
[0007] Thus there has been renewed interest in fire flooding
techniques which can in principle recover close to eighty percent
of the oil in place and upgrade the oil by in-situ thermal coking.
This would produce an oil similar to that from coking of surface
mined and SAGD produced heavy oils. Unfortunately, fire flooding is
difficult to control and the in-situ coking can plug the deposit.
Thus there have been only a few pilot operations.
[0008] Technology that would promote economic extraction of such
deposits and produce a higher quality oil is thus much needed. With
worldwide consumption of petroleum increasing year-by-year,
production of oil from heavy crude oil deposits in accordance with
the present invention can play an important role in limiting
dependence on importation of petroleum to meet consumption
demand.
BRIEF SUMMARY OF THE INVENTION
[0009] It has now been found that heavy oil can be upgraded
downhole to produce a lower viscosity oil which does not require
dilution for transport to a refinery or an upgrader. By contact
with steam at a temperature high enough to promote steam cracking
of the heavy oil in-situ, upgraded oil is produced. Preferably,
coke formed can react with the steam to form hydrogen and/or
methane.
[0010] In one embodiment of the present invention, steam from a
conventional surface boiler is mixed with sufficient oxygen wherein
the oxygen is combusted with carbon to form CO.sub.2. The fluid
temperature would be high enough to heat the oil to a temperature
sufficient to induce cracking of the oil. In this embodiment, all
the heat of combustion released is delivered to the reservoir to
enhance steam cracking. The steam and oxygen present react with
carbon thus maintaining reservoir porosity. The optional injection
of catalyst into the steam combustion product stream further
promotes cracking of the heavy oil and allows control of pH.
[0011] Temperatures above the critical temperature of steam are
required. Temperatures of 800 to 1000 degrees Fahrenheit are
advantageous allowing production of upgraded oil and methane. Even
higher temperatures allow production of hydrogen and further
upgrading of the in place oil. The required oxygen may be supplied
either as air, oxygen enriched air, or pure oxygen. Use of pure
oxygen minimizes dilution of produced methane or hydrogen. The
amount of oxygen should be such that upon injection into a heavy
oil reservoir, in-situ combustion releases enough heat to raise the
temperature sufficiently for steam cracking of the oil. Such
temperatures are well known in the art.
[0012] It is preferred that reservoir oil be heated at least to a
temperature of 700 degrees Fahrenheit. Thus steam temperatures
above this level are desired. This enables in-situ refining of
heavy crude oils with minimal formation of carbon deposits. Not
only is oil viscosity reduced by heating the oil, as in
conventional steam flooding, but also intrinsic viscosity is
reduced by thermal cracking the oil in the presence of steam
thereby altering its chemical composition. Unlike conventional
in-situ combustion, carbon produced in the cracking process reacts
with steam and is converted to a mixture comprising methane and
carbon dioxide (or hydrogen and carbon oxides at higher
temperatures), thermodynamically favored reactions, expressed as
follows: C+2H.sub.2O=2H.sub.2+CO.sub.2 & C+2H.sub.2=CH.sub.4
-or- 2C+2H.sub.2O=CH.sub.4+CO.sub.2
[0013] Free hydrogen is produced from carbon even at temperatures
as low as 700 degrees Fahrenheit. Thus, hydrogen is available for
in situ desulfurization of reservoir oil. Both cracking and
desulfurization lower oil viscosity thereby upgrading the oil.
Sweep efficiency is improved via enhancement of mobility and
control of reservoir permeability as a result of the reduction of
intrinsic oil viscosity. Thus effective recovery of the oil in
place can exceed ninety percent.
[0014] In another embodiment of the present invention, steam at a
temperature high enough for steam cracking may be produced by
downhole combustion of a fuel supplied from the surface together
with water. The water is converted to steam of a desired
temperature downhole thereby eliminating the need for a surface
steam boiler. In this embodiment all combustion products are
delivered downhole and boiler heat losses are avoided. Any known
combustor system may be used.
[0015] Preferably, a catalytic combustion system is provided
downhole. Catalytic combustors have two interrelated features that
allow downhole combustion of hydrocarbon fuels for generation of a
higher temperature steam: combustion stability and soot free
operation. Operation within normal flame stability limits is not
required allowing use of low BTU fuels. This approach retains all
the benefits of downhole steam generation while adding the benefits
of in-situ oil upgrading and thereby significantly reducing costs
and improving sweep efficiency.
[0016] In another embodiment of the present invention,
stoichiometric amounts of hydrocarbon fuel and a gas containing
oxygen are combusted downhole in a catalytic combustor to produce
heat and an admixture comprising carbon dioxide and steam. Water is
injected into the hot combustion products to produce a cooled
mixture at a temperature of about 1160 degrees Fahrenheit, a
temperature more than adequate for rapid cracking of oils. The
cooled mixture is then passed into contact with the heavy oil
deposit. The mixture temperature may be varied to maintain the oil
deposit at a desired temperature depending on the degree of
cracking desired.
[0017] In another embodiment of the present invention, steam from a
conventional surface boiler is admixed with compressed oxygen in
sufficient quantity and reacted with carbon to form CO.sub.2. The
mixture temperature is increased by at least one hundred degrees
Kelvin, more preferably by at least one hundred fifty degrees
Kelvin. The amount of oxygen provided may be varied to maintain the
oil deposit at a desired temperature depending on the degree of
cracking desired. Optionally, compressed air or oxygen-enriched air
may be used to supply the required oxygen.
BRIEF DESCRIPTION OF THE DRAWINGS
[0018] FIG. 1 depicts a diagrammatic representation of one
embodiment of a steam production and oil extraction system
according to the present invention.
[0019] FIG. 2 depicts a diagrammatic representation of another
embodiment of a steam production and oil extraction system
according to the present invention.
DETAILED DESCRIPTION OF THE INVENTION
[0020] The present invention yields a superior and more flexible
enhanced oil recovery process comprising methods for providing
steam downhole at a temperature high enough for in-situ steam
cracking of oil deposits and for production of methane from coke.
If available, supercritical temperature steam can be supplied from
the surface. Catalysts known in the art including boric acid and
potassium hydroxide may be added to the steam admixture, to enhance
cracking efficiency and/or the reaction of carbon with steam.
[0021] The hot fluid comprising steam is injected into the
oil-bearing formation to provide the heat and the hydrogen
necessary for production of methane from carbon. Steam cracking of
the oil reduces oil viscosity and disrupts oil-sand bonding. The
hot fluid may be injected into an oil-bearing reservoir via a
vertical well or, more advantageously, through a horizontal well.
In huff-and-puff operation, injection of the hot fluid is stopped
after a chosen portion of the reservoir has reached a selected
temperature. Oil is then withdrawn through the heated zone into the
injection well which becomes the production well. Preferably, the
heated portion of the reservoir may be allowed to soak at
temperature for a selected period of time, allowing for greater
reaction of the oil in contact with steam. This permits lower
reaction temperatures. The result is a process system that offers
numerous benefits with a number of controllable variables. Because
oil fields differ and the task of recovery varies in each case,
these variables can be adjusted to adapt the process to fit the
particular reservoir conditions.
[0022] As in conventional steam flooding, heat and pressure may be
used drive oil from the source and towards a producing well.
Gravity drainage may be employed. Because steam cracking reduces
the oil molecular weight, the oil remains fluid even at low ambient
temperatures. Thus, flow through the production well is no longer
limited by heat loss during transport to the surface.
[0023] Optionally, a catalyst may be added to the steam to enhance
cracking of the oil in the reservoir while weakening molecular
polarity thereby promoting displacement of the oil from the sand.
Water/steam miscible catalysts include materials such as boria,
potassium and sodium carbonate as well as compounds of known
catalytic metals including nickel, cobalt and chromium. The
catalysts injected can be selected to adjust the pH of the steam.
This can help control permeability of oil-bearing clays, the
swelling of which is a function of pH.
[0024] The CO.sub.2 and methane produced in the steam cracking
reactions offer pressure maintenance for enhanced product flow. The
downhole CO.sub.2 displaces the oil through preferential adsorption
of the CO.sub.2 in the sand/clay particles, although at higher
temperatures this effect can be limited. Where the presence of
nitrogen would unduly dilute associated natural gas, pure oxygen
can be used instead of air to supply the oxygen. For very deep
wells, the costs of compressing air can outweigh the costs of pure
oxygen production, leading to preferential use of pure oxygen.
Using gaseous oxygen instead of air reduces the amount of oxidant
that must be compressed. The capability to control fluid pH enables
control of clay permeability in clay-bearing strata, also important
in improving sweep efficiency.
[0025] FIG. 1 depicts an application 10 of the present invention
within a sloping viscous oil deposit. Injection well 12 extends
vertically downward from surface 14 to oil reservoir formation 20.
Injection well 12 is in fluid communication with horizontal well
section 16 which proceeds along a lower elevation region of
formation 20. Formation 20 is underlain by impermeable region 22
and capped by impermeable layer 24. The hot fluid flow 18 enters
formation 20 migrating upward from horizontal well section 16 into
formation 20. The reacted oil will migrate downslope and collect
within formation 20. In a huff and puff operation, reacted oil may
be recovered through injection well 12 and horizontal well section
16 after termination of fluid injection.
[0026] FIG. 2 depicts an application 110 of the present invention
within a heavy oil deposit. Injection wells 112 and 113 extend
vertically from surface 114 to the bottom of deposit 120. Injection
well 112 and then extends horizontally along horizontal well
section 116, along the bottom of deposit 120 which slopes uphill.
Injection well 113 similarly extends horizontally along horizontal
well section 117 along the bottom of deposit 120. Deposit 120 is
underlain by impermeable region 122 and capped by impermeable layer
124. Hot fluid flow 118 enters deposit 120 migrating upward from
horizontal well sections 116 and 117 into deposit 120. Production
well 126 extends vertically from surface 114 to a downhill region
of deposit 120 where it can collect and extract cracked oil. A
horizontal section, horizontal well section 128, of production well
126, extends nominally perpendicular to horizontal well sections
116 and 117 in a downhill location of deposit 120. Hot
steam-bearing fluid may be provided from the surface or generated
downhole using a catalytic combustor.
[0027] This invention improves sweep efficiency through steam
cracking and provides improved downhole temperature control. In
contrast, conventional surface generation of steam provides oil
temperatures that are too low for effective steam cracking thereby
producing unrefined oil and limiting the achievable recovery of oil
in place. Since in-situ steam cracking improves crude quality and
oil recovery efficiency, the present invention significantly
reduces the oil price required for profitability after extraction
thus further augmenting the advantage compared to conventional
steam flooding. No coking of produced oil is needed since
sufficient coking can occur in-situ with the coke reacted with
steam to produce methane and carbon dioxide. The present invention
effectively increases the recoverable reserves of heavy oils by
allowing high recovery of oil in place and also offers benefits in
enhanced recovery of lighter oils and oil from shale. Methane
produced can be utilized as fuel for the steam production.
[0028] Although the invention has been described in considerable
detail, it will be apparent that the invention is capable of
numerous modifications and variations, apparent to those skilled in
the art, without departing from the spirit and scope of the
invention. Such modifications and variations should be considered
within the scope of the present invention.
* * * * *