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Embodiments of the invention relate to methods and systems for in situ electric heating with steam assisted oil recovery.
In order to recover oils from certain geologic formations, steam can be injected to increase the mobility of the oil within the formation via such processes known as steam assisted gravity drainage (SAGD). The oil that is made mobile enough to flow through the formation due to gravity gathers in a well for production. Cost of prior approaches to drain reservoirs containing the oil with a natural viscosity that inhibits the recovery makes any inefficiency a problem. Various factors may prevent achieving performance levels as high as desired or needed for economic success.
One example of the factors influencing the economic success of the SAGD includes duration of startup time while steam is circulated without production to establish fluid communication between an injector and producer well pair. In addition, heterogeneities in the formation can prevent full development of chambers formed in the formation by the steam if migration of the steam is blocked. The chambers also tend to develop upward with less lateral development since gravity influences required for momentum decreases as the chambers spread. As a result, percentage of the oil recoverable from areas located between two adjacent steam chambers and toward bottoms of the chambers diminishes relative to where the chambers form and may merge together in the formation. Speed of the lateral development for the chambers further influences rate at which the oil can be produced.
Therefore, a need exists for improved methods and systems for developing chambers in reservoirs formed during steam assisted oil recovery.
In one embodiment, a method of obtaining recovery from a reservoir includes supplying electric current to an auxiliary well offset in a lateral direction from a well pair arranged for steam assisted gravity drainage of oil in a formation. The method further includes injecting steam into the formation through an injector of the well pair and producing through a producer of the well pair both oil heated by the steam and water condensate to develop within the formation a steam chamber. Heating of the oil as a result of the electric current being supplied to the auxiliary well facilitates lateral development of the steam chamber.
According to one embodiment, a method of obtaining recovery from a reservoir includes passing electric current through a formation between a production well and an auxiliary well offset in a lateral direction from the production well. Further, injecting steam into the formation and producing through a production well water condensate and oil that is from the formation and is heated by the steam develops within the formation a steam chamber that the production well is disposed beneath. The passing of the electric current occurs during the injecting and the producing in order to heat the oil for promoting lateral development of the steam chamber.
For one embodiment, a method of obtaining recovery from a reservoir includes creating an electric potential between a well pair and an auxiliary well offset in a lateral direction from the well pair and circulating steam through an injector of the well pair and through a producer of the well pair while creating the electric potential. The circulating of the steam and the electric potential heats oil in an area of formation between the injector and the producer in order to initiate fluid communication between the injector and the producer. After the fluid communication is established, injecting steam into the formation through the injector and producing through the producer water condensate and the oil heated by the steam develops within the formation a steam chamber, in which development in the lateral direction is facilitated by the oil being heated due to the electric potential.
The invention, together with further advantages thereof, may best be understood by reference to the following description taken in conjunction with the accompanying drawings.
Embodiments of the invention relate to systems and methods to recover oil from a formation. In operation, a steam chamber develops as a result of steam injection into the formation and the recovery of fluids including the oil through a production well. An auxiliary well spaced in a lateral direction from the production well helps ensure development of the steam chamber as desired. The auxiliary well may enable heating of the formation through establishing an electric potential between the auxiliary well and the production well or by resistive heating of material forming the auxiliary well. Further, the auxiliary well may provide a flow path for solvent or gas injection to facilitate the recovery through the production well.
An auxiliary well 106 extends through the formation at a location offset (e.g., at least 5 meters) in the lateral direction from the first injector 101 and the first producer 102. The auxiliary well 106 may include a horizontal borehole length that is disposed higher in the formation relative to the horizontal borehole lengths of the first injector 101 and the first producer 102. Position of the auxiliary well 106 relative to the injectors 101, 103 and the producers 102, 104 thus locates the auxiliary well 106 between and parallel to well pairs used for the SAGD.
For some embodiments, the auxiliary well 106 couples to a power source 108 that supplies direct or alternating current to one or more electrodes 110 that may be spaced from one another along the length of the auxiliary well 106. Completion of the auxiliary well 106 other than at the electrodes 110 may include non-conductive tubing, which conveys and separates the electrodes 110 downhole. In operation, the power source 108 applies a voltage between the electrodes 110 used as anodes and conductive tubing such as steel casing of both the injectors 101, 103 and the producers 102, 104 forming cathodes.
Current density in the formation 100 increases around the injectors 101, 103 and the producers 102, 104 as the electric current 200 passes toward and concentrates at the injectors 101, 103 and the producers 102, 104. This relative higher current density around the injectors 101, 103 and the producers 102, 104 may facilitate heating of the oil and establishing fluid communication between the first injector 101 and the first producer 102 and between the second injector 103 and the second producer 104 as required to bring production online. Startup with steam circulation alone through each of the injectors 101, 103 and the producers 102, 104 can take several months to establish the fluid communication. Given cost of steam generation and such expensive production delay, supplementing heating resulting from the circulation of the steam concurrent with the resistive heating due to the electric current 200 generated using the electrodes 110 can shorten a time period for the startup.
Conductivity between the auxiliary first well 506 and each of the injection, production and auxiliary second wells 501, 502, 507 changes as the first and second SAGD chambers 530, 531 develop. Measuring the conductivity hence provides an indication of the development of the first and/or second SAGD chambers 530, 531 and/or potential merging together of the first and/or second SAGD chambers 530, 531 into one. Since electrodes utilized in the first and/or second auxiliary wells 506, 507 may be spaced out like the electrodes 110 shown in
Adjusting operation parameters based on information gained from measurements of the conductivity provides ability to manipulate development of the chambers 530, 531, 532 so that as much of the oil is recovered from the formation as economical as possible. For example, the conversion of the auxiliary second well 507 from anode to cathode may be decided in view of the measurements being indicative of inhibited upward development of the second SAGD chamber 531. In some embodiments, the measurements may dictate flow rates and locations for steam introduction at different discrete lengths of each of the injection wells 501.
The resistive heating well 606 may not provide an anode-cathode relation with the upper and lower wells 601, 603, 602, 604. Rather, resistive heating of material, such as the proppant 607, that forms part of the heating well 606 transfers heat from the proppant 607 to a surrounding area of the formation 600 resulting in reducing viscosity of the oil. The proppant 607 relative to conventional electrodes provide greater surface area to deploy current from a power supply 608. Current density spreads out across the surface area of the proppant 607 limiting degradation of the proppant 607 and undesired coking around the proppant 607.
For some embodiments, the resistive heating well 606 provides a flow path for injection of gas or solvent for the oil, such as described herein. The proppant 607 if used for heating may transfer heat to the gas or solvent being injected. Since the solvent or gas is thus heated in situ, employing the heating well 606 for injection of the gas or solvent avoids thermal loss from conveying fluids downhole that are preheated at surface.
The preferred embodiment of the present invention has been disclosed and illustrated. However, the invention is intended to be as broad as defined in the claims below. Those skilled in the art may be able to study the preferred embodiments and identify other ways to practice the invention that are not exactly as described herein. It is the intent of the inventors that variations and equivalents of the invention are within the scope of the claims below and the description, abstract and drawings are not to be used to limit the scope of the invention.
This application is a non-provisional application which claims benefit under 35 USC §119(e) to U.S. Provisional Application Ser. No. 61/263,547 filed Nov. 23, 2009, entitled “IN SITU HEATING FOR RESERVOIR CHAMBER DEVELOPMENT,” which is incorporated herein in its entirety.
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Number | Date | Country | |
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20110120710 A1 | May 2011 | US |
Number | Date | Country | |
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61263547 | Nov 2009 | US |