Wells – Processes – Distinct – separate injection and producing wells
Reexamination Certificate
2000-03-16
2002-03-19
Bagnell, David (Department: 3672)
Wells
Processes
Distinct, separate injection and producing wells
C166S267000, C166S279000, C166S310000, C166S075120, C208S309000, C208S045000
Reexamination Certificate
active
06357526
ABSTRACT:
FIELD OF THE INVENTION
This invention relates to recovering a pumpable crude oil from a reservoir of heavy oil or bitumen by the steam-assisted gravity drainage (SAGD) process, and more particularly to solvent deasphalting to remove an asphaltene fraction from the heavy oil or bitumen to yield the pumpable synthetic crude, and to combusting the asphaltene fraction to supply heat for generation of the injection steam.
BACKGROUND
Heavy oil reservoirs contain crude petroleum having an API gravity less than about 10 which is unable to flow from the reservoir by normal natural drive primary recovery methods. These reservoirs are difficult to produce due to very high petroleum viscosity and little or no gas drive. Bitumen, usually as tar sands, occur in many places around the world.
The steam-assisted gravity drainage (SAGD) process is commonly used to produce heavy oil and bitumen reservoirs. This generally involves injection of steam into an upper horizontal well through the reservoir to generate a steam chest that heats the petroleum to reduce the viscosity and make it flowable. Production of the heavy oil or bitumen is from a lower horizontal well through the reservoir disposed below the upper horizontal well.
Representative references directed to the production of crude petroleum from tar sands include Canadian Patent Application 2,069,515 by Kovalsky; U.S. Pat. No. 5,046,559 to Glandt; U.S. Pat. No. 5,318,124 to Ong et al; U.S. Pat. No. 5,215,146 to Sanchez; and Good, “Shell/Aostra Peace River Horizontal Well Demonstration Project,” 6
th
UNITAR Conference on Heavy Crude and Tar Sands (1995), all of which are hereby incorporated herein by reference. Most of this technology has been directed to improving reservoir production characteristics. Surprisingly, very little attention has been directed to incorporating on-site downstream processing into the upstream field processing of the heavy oil or bitumen for improving the efficiency of operation and overall field production economy.
The heavy oil or bitumen produced by the SAGD and similar methods requires large amounts of steam generated at the surface, typically at a steam-to-oil ratio (SOR) of 2:1, i.e. 2 volumes of water have to be converted to injection steam for each volume of petroleum that is produced. Usually natural gas is used as the fuel source for firing the steam boilers. It is very expensive to supply the natural gas to the boilers located near the injection wells, not to mention the cost of the natural gas itself.
Another problem is that when the heavy oil or bitumen is produced at the surface, it has a very high viscosity that makes it difficult to transport and store. It must be kept at an elevated temperature to remain flowable, and/or is sometimes mixed with a lighter hydrocarbon diluent for pipeline transportation. The diluent is expensive and additional cost is incurred to transport it to the geographically remote location of the production. Furthermore, aspahaltenes frequently deposit in the pipelines through which the diluent/petroleum mixture is transported.
There is an unmet need in the art for a way to reduce the cost of steam generation and the cost and problems associated with heavy oil and/or bitumen surface processing and transporting. The present invention is directed to these unfulfilled needs in the art of SAGD and similar heavy oil and/or bitumen production.
SUMMARY OF THE INVENTION
The present invention provides a process and systems for producing heavy oil or bitumen economically by steam-assisted gravity drainage (SAGD), upgrading the heavy oil or bitumen into a synthetic crude, and using the bottom of the barrel to produce steam for injection into the reservoir.
Broadly, the present invention provides a process for recovering a pumpable synthetic crude oil from a subterranean reservoir of heavy oil or bitumen, comprising the steps of: (a) injecting steam through at least one injection well completed in communication with the reservoir to mobilize the heavy oil or bitumen; (b) producing the mobilized heavy oil or bitumen from at least one production well completed in the reservoir; (c) fractionating the heavy oil or bitumen produced from step (b) at a location adjacent to the reservoir into a first fraction as a minor amount of the heavy crude comprising a gas oil fraction and second fraction comprising a residue; (d) solvent deasphalting the second fraction from step (c) to form an asphaltene fraction and a deasphalted oil fraction essentially free of asphaltenes; (e) combusting the asphaltene fraction from step (d) to produce the steam for injection step (a); and (e) blending the first fraction from step (c) with the deasphalted oil fraction from step (d) to form a pumpable synthetic crude oil. The fractionation is preferably performed under atmospheric pressure. The asphaltene fraction from step (d) can be supplied as a liquid to the combustion step (e), or alternatively the asphaltene fraction from step (d) can be pelletized to obtain asphaltene pellets for supply to the combustion step (e).
The combustion step (e) preferably comprises combustion of the asphaltenes in a boiler to produce the injection steam for step (a). By this process, the solvent deasphalting step (d) can be performed at a first location to which the produced heavy oil or bitumen is transported, and the asphaltene fraction can be transported from the first location to a plurality of boilers spaced away from the first location, preferably adjacent to the injection well or wells. The boiler is preferably a circulating fluid bed boiler.
In an alternate embodiment, the combustion step (e) comprises gasification of the asphaltene fraction to produce a synthesis gas and the injection steam for step (a). The process can include recovering CO
2
from the synthesis gas and injecting the CO
2
into the reservoir. A portion of the steam produced from gasification can be expanded in a turbine to generate electricity.
Another aspect of the invention is a process for recovering a pumpable crude oil from a subterranean reservoir of heavy oil or bitumen. The process comprises the steps of: (a) injecting steam through one or more injection wells completed in communication with the reservoir to mobilize the heavy oil or bitumen; (b) producing the mobilized heavy oil or bitumen from at least one production well completed in the reservoir; (c) solvent deasphalting at least a portion of the heavy oil or bitumen produced from step (b) to form an asphaltene fraction and a deasphalted oil fraction essentially free of asphaltenes; (d) pelletizing the asphaltene fraction from step (c) to obtain asphaltene pellets; and (e) combusting the asphaltene pellets from step (d) to produce the steam for injection step (a). The combustion step (e) in one embodiment comprises combustion in at least one boiler to produce the injection steam for step (a). In one embodiment, the solvent deasphalting step (d) is preferably performed at a first location and the asphaltene fraction is transported from the first location to a plurality of boilers spaced away from the first location adjacent to the one or more injection wells. The at least one boiler is preferably a circulating fluid bed boiler. In an alternate embodiment, the combustion step (e) comprises gasification of the asphaltene pellets to produce a synthesis gas and the injection steam for step (a). The process can include the steps of recovering CO
2
from the synthesis gas and injecting the CO
2
into the reservoir with the steam. A portion of the steam generated from gasification can be expanded in a turbine to generate electricity.
Another aspect of the invention is the provision of a system for producing a pumpable synthetic crude oil. The system includes a subterranean reservoir of heavy oil or bitumen; at least one injection well completed in the reservoir for injecting steam into the reservoir to mobilize the heavy oil or bitumen; at least one production well completed in the reservoir for producing the mobilized heavy oil or bitumen; an atmospheric flash unit for fractionating the heavy oil or b
Abdel-Halim Tayseer
Subramanian Murugesan
Bagnell David
Kellogg Brown & Root Inc.
Kellogg Brown & Root, Inc.
Walker Zakiya
LandOfFree
Field upgrading of heavy oil and bitumen does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Field upgrading of heavy oil and bitumen, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Field upgrading of heavy oil and bitumen will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-2827266