U.S. patent application number 10/244320 was filed with the patent office on 2004-03-18 for downhole upgrading of oils.
Invention is credited to Limbach, Kirk Walton.
Application Number | 20040050547 10/244320 |
Document ID | / |
Family ID | 31991885 |
Filed Date | 2004-03-18 |
United States Patent
Application |
20040050547 |
Kind Code |
A1 |
Limbach, Kirk Walton |
March 18, 2004 |
Downhole upgrading of oils
Abstract
Oils present in oil reservoirs can be upgraded by high
temperature cracking through the injection of oxygen into the
reservoir and combusting the oils to generate heat. By employing
injection wells and production wells, the oxygen may be placed into
the reservoir increasing the flux of oxygen present as well as the
temperature and cracking severity needed to produce upgraded
oil.
Inventors: |
Limbach, Kirk Walton;
(Dresher, PA) |
Correspondence
Address: |
Philip H. Von Neida
Intellectual Property Dept.
The BOC Group, Inc.
100 Mountain Ave.
Murray Hill
NJ
07974
US
|
Family ID: |
31991885 |
Appl. No.: |
10/244320 |
Filed: |
September 16, 2002 |
Current U.S.
Class: |
166/260 |
Current CPC
Class: |
E21B 43/243
20130101 |
Class at
Publication: |
166/260 |
International
Class: |
E21B 043/24 |
Claims
Having thus described the invention, what I claim is:
1. A method for cracking oil in an oil reservoir comprising
injecting oxygen into said oil reservoir and igniting said oil.
2. The method as claimed in claim 1 further comprising a production
well.
3. The method as claimed in claim 1 wherein said cracked oil is
recovered through said production well.
4. The method as claimed in claim 1 wherein said oil comprises
heavy oil and tar sands.
5. The method as claimed in claim 1 wherein said cracking is
performed at a temperature greater than 400.degree. C.
6. The method as claimed in claim 1 wherein said cracking is
performed at a temperature greater than 500.degree. C.
7. The method as claimed in claim 1 wherein said oxygen is pure
oxygen or oxygen-enriched air.
8. The method as claimed in claim 7 wherein said oxygen or
oxygen-enriched air is produced by an air separation facility.
9. The method as claimed in claim 1 wherein ignition is provided by
an electronic device or by steam heat.
10. The method as claimed in claim 1 further comprising injecting
water into said oil reservoir.
11. An in-situ combustion process for recovering oil from an
underground oil containing reservoir comprising the steps of:
injecting oxygen into said reservoir through an injection well,
combusting and cracking said oil; producing cracked oil, and
recovering said cracked oil through a production well.
12. The process as claimed in claim 11 wherein said injection well
is vertical and said production well is horizontal.
13. The process as claimed in claim 11 wherein said injection well
and said production well are horizontal.
14. The process as claimed in claim 11 wherein said production well
and said injection well are perpendicular to each other.
15. The process as claimed in claim 11 wherein there are a
plurality of injection wells.
16. The process as claimed in claim 11 wherein there are a
plurality of production wells.
17. The process as claimed in claim 11 wherein said combustion
takes place at temperatures greater than 400.degree. C.
18. The process as claimed in claim 11 wherein said combustion
takes place at temperatures greater than 400.degree. C.
19. The process as claimed in claim 11 further comprising
recovering carbon dioxide from said production well.
20. The process as claimed in claim 11 wherein said injection well
is located near the top of said oil bearing reservoir and said
production well is located near the bottom of said oil bearing
reservoir.
21. The process as claimed in claim 11 wherein a catalyst is
present in said production well.
Description
FIELD OF THE INVENTION
[0001] The present invention relates to the injection of oxygen or
oxygen-enriched air into an oil reservoir causing in-situ
combustion to occur and the oil to crack into lighter
fractions.
BACKGROUND OF THE INVENTION
[0002] In conventional in-situ combustion (ISC) processes, also
called fire flooding or heavy oil air injection (HOAI), vertical
wells are used for injection of air and typically water for the
production of oil. The distance between the wells is often
substantial and oil and water vaporized by the combustion and
upgrading process condense in the cooler parts of the reservoir,
travel through the heavy oil and are produced via well techniques.
Due to the highly viscous oils through which these lighter fluids
must travel, it may be difficult to maintain production and
pressure may build on the injection side. This may be one reason
for failure of field applications of such technology in the past. A
short distance process may be utilized in which a vertical or
horizontal injection well and a horizontal producer well are used
so that displacement of oil can be achieved along the horizontal
producer well. A combustion front propagates through the reservoir
above the horizontal well allowing good communication of the
upgraded oil and the production well. One example of such a process
is the Toe to Heel Air Injection (THAI) process. A catalyst may be
placed in the producer well to obtain further upgrading of the oil,
as in the CAPRI process.
[0003] The Combustion Override Split-production Horizontal well
(COSH) process also uses air injected into the reservoir to
generate steam and heat in-situ. A well arrangement is used to
segregate and control fluid flows and thereby reduce early oxygen
breakthrough as well as sanding and gas locking of downhole pumps.
The well arrangement makes use of an air injection well, gas
producer well which removes excess nitrogen and other gases from
near the top of the pay zone, and horizontal well to recover oil
from a lower portion of the pay zone. The COSH process has an
advantage over the THAI and CAPRI processes in that problems which
arise from the handling of nitrogen and other gases are
reduced.
[0004] Other examples of short distance displacement processes
include Steam Assisted Gravity Drainage (SAGD) and Vapor Extraction
(VAPEX). In the SAGD process, steam enters through a horizontal
injection well and travels a relatively short distance to a
horizontal production well. The heating of heavy viscous oils
between these wells allows the oils to flow to the production well.
The VAPEX process is similar to SAGD but hydrocarbon vapor is used
instead of steam. Asphaltene precipitation is caused by the mixing
of solvent and oil and provides for an in-situ upgrading of the
oil.
SUMMARY OF THE INVENTION
[0005] The present invention provides for a method for cracking oil
in an underground oil reservoir comprising injecting oxygen into
the oil reservoir and igniting the oil therein. The combustion
associated with the high influx of oxygen will generate high
temperatures which will cause the oil to crack into lighter
fractions to form coke or carbonaceous solids from the heaviest
compounds in the oil such as asphaltenes.
[0006] The present invention also provides for injecting oxygen
into the oil reservoir such that in-situ combustion can take place
for recovering the oil through one or more production wells.
DETAILED DESCRIPTION OF THE INVENTION
[0007] The present invention provides for an in-situ combustion
process for recovering oil from an underground oil containing
reservoir. The process comprises injecting oxygen into the oil
reservoir. This oxygen will react to combust the oil which causes
heat generation. The resulting high temperatures will cause the oil
to crack into lighter fractions. The invention is most applicable
for heavy oil or tar sands. By injecting oxygen and igniting the
oil in the presence of the oxygen, high temperatures greater than
400.degree. C. and preferably greater than 500.degree. C. cause the
oil to crack to form lighter more valuable products, as well as
coke or carbonaceous solids. In addition, higher temperatures are
desirable to facilitate the formation of CO.sub.2. Less desirable
oxygen containing hydrocarbons may be formed at lower
temperatures.
[0008] For purposes of the present invention, oxygen can mean pure
100% oxygen gas, but it can also include oxygen-enriched air which
contains oxygen in an amount greater than 25%. Purification of the
oxygen allows for a significantly higher flux of oxygen to be
placed into the well due to the reduction of associated nitrogen
which would be present in air. This aids in increasing the
temperature which increases the cracking severity but also provides
for reducing the need to handle nitrogen in the gases at the
production well.
[0009] In one embodiment of the present invention, a horizontal
producer well and vertical injection well is employed. The
horizontal producer well will result in a short distance
displacement process whereby oil and water vaporized by the intense
heat of the oil combustion front can travel freely to the
horizontal producer well. This will allow the large flux of oxygen
into the reservoir to continue unhampered by upstream blockages.
Injectivity of oxygen-containing gas is increased by the combustion
of carbonaceous materials near the injection well. In a second
embodiment, two sets of horizontal wells may be employed whereby
oxygen is injected in one set of horizontal wells and oil is
produced from a lower perpendicular set of horizontal wells. The
oxygen, when injected into the reservoir, may be ignited by an
electronic device or other form of heat, such as steam, which will
increase local temperature in the reservoir
[0010] Water may also be injected with the oxygen once the
combustion zone has been established. The steam generated in this
manner is an efficient means to transfer heat to the oil. The
cracked oils will be of higher quality in that they are relatively
light, virtually free of metals and have a lower sulfur content
than the untreated oils. The temperatures greater than 400.degree.
C. by which the oils are cracked will also improve carbon dioxide
production. The carbon dioxide is known to reduce viscosity and
interfacial tension in the oil as well as to cause swelling of the
oil in order to enhance production. The use of oxygen necessarily
means that less nitrogen or no nitrogen is present in the reservoir
such that a much higher flux of oxygen is provided and consequently
higher temperatures and higher concentrations of carbon dioxide are
present.
[0011] One means of obtaining the oxygen employed in the present
invention is from an air separation plant which can be on-site or
very close to the actual production wells. In preferred embodiments
of the present invention, the well arrangement having a first
vertical gas injection well located near the top of the oil bearing
portion of the reservoir and a horizontal oil production well
located near the bottom of the reservoir. The oxygen would be
injected into the first well, combusted and drive the cracked oils
into the horizontal oil production well where the oil can be
recovered by conventional means. In another preferred embodiment,
several horizontal gas injection wells running substantially
parallel to each other are located near the top of the oil bearing
portion of the reservoir and several oil producing wells also
horizontal and substantially parallel to each other are situated
perpendicular to the gas injection wells. This provides additional
advantages in that the gas injection wells could be used one at a
time to upgrade the reservoir oils in the vicinity of that
particular gas injection well. The injection and production wells
may be formed of any material that is commonly employed in the oil
production industry. One example would be a perforated stainless
steel tubing of dimensions sufficient to deliver oil from the
reservoir.
[0012] While this invention has been described with respect to
particular embodiments thereof, it is apparent that numerous other
forms and modifications of the invention will be obvious to those
skilled in the art. The appended claims of this invention generally
should be construed to cover all such obvious forms and
modifications which are within the true spirit and scope of the
present invention.
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