None.
Embodiments of the invention relate to producing hydrocarbons with multiple horizontal wells through which injection processes precondition and displace the hydrocarbons.
Bitumen recovery from oil sands presents technical and economic challenges due to high viscosity of the bitumen at reservoir conditions. Steam assisted gravity drainage (SAGD) provides one process for producing the bitumen from a reservoir. During SAGD operations, steam introduced into the reservoir through a horizontal injector well transfers heat upon condensation and develops a steam chamber in the reservoir. The bitumen with reduced viscosity due to this heating drains together with steam condensate along a boundary of the steam chamber and is recovered via a producer well placed parallel and beneath the injector well.
However, costs associated with energy requirements for the SAGD operations limit economic returns and can make thin pay zones uneconomic to recover. Other past processes proposed to rely on cyclic injections but failed to recover enough of the bitumen for commercial success. Further, prior displacement methods utilized in reservoirs containing mobile hydrocarbons cannot enable recovery of the bitumen where immobile since the bitumen provides a barrier to flow between wells.
Therefore, a need exists for methods and systems for recovering hydrocarbons from oil sands including thin pay zones of immobile bitumen.
In one embodiment, a method of recovering hydrocarbons includes injecting during a first time a conditioning fluid through first and second wells and into a formation along lateral spaced apart and parallel horizontal lengths of the first and second wells. The method further includes producing the hydrocarbons recovered as backflow along the lengths of the first and second wells during a second time after the first time. Then, injecting the conditioning fluid into the formation along the length of the second well while producing the hydrocarbons along the length of the first well alternates with injecting the conditioning fluid into the formation along the length of the first well while producing the hydrocarbons along the length of the second well, thereby establishing fluid communication between the first and second wells. Next, injecting a displacement fluid into the formation along the length of the first well sweeps the hydrocarbons toward the second well and occurs while producing, along the length of the second well, the hydrocarbons being displaced.
For one embodiment, a method of recovering hydrocarbons includes injecting a conditioning fluid through first and second wells and into a formation at dispersed locations along parallel horizontal lengths of the first and second wells such that the injecting via the first well is offset in a lateral direction from the second well and aligned between the dispersed locations of the second well across from portions of the second well without fluid communication to the formation. Producing the hydrocarbons recovered as backflow at the dispersed locations along the first and second wells occurs after the injecting of the conditioning fluid. Then, injecting a displacement fluid into the formation via the dispersed locations along the first well sweeps the hydrocarbons toward the second well and occurs while producing, at the dispersed locations along the second well, the hydrocarbons being displaced.
A more complete understanding of the present invention and benefits thereof may be acquired by referring to the follow description taken in conjunction with the accompanying drawings.
Turning now to the detailed description of the preferred arrangement or arrangements of the present invention, it should be understood that the inventive features and concepts may be manifested in other arrangements and that the scope of the invention is not limited to the embodiments described or illustrated. The scope of the invention is intended only to be limited by the scope of the claims that follow.
For some embodiments, methods and systems produce petroleum products with multiple horizontal wells through which injection processes precondition and displace the hydrocarbons in a formation. The wells extend through the formation spaced apart from one another in a lateral direction. Before fluid communication is established between the wells, cyclic injections and production of resulting backflow initiates conditioning of immobile products. Alternating between injection and production at adjacent wells may then facilitate establishing the fluid communication. After the fluid communication is established, a displacement procedure sweeps the hydrocarbons from one of the wells used for injection toward an adjacent one of the wells used for production.
As shown viewed transverse to the horizontal lengths, all the wells 111, 112, 113 in some embodiments align in a common horizontal plane or otherwise have the horizontal length in substantial horizontal alignment with one another. A lateral distance of between 5 and 50 meters may separate the wells 111, 112, 113 from one another. Costs of cycling depicted and described with respect to
For some embodiments, flow control devices 200 dispersed along the horizontal lengths of the wells 111, 112, 113 facilitate uniform or patterned injection and/or production along the horizontal lengths of the wells 111, 112, 113. The flow control devices 200 provide fluid communication from inside the wells 111, 112, 113 to the formation and can include orifices, perforations or slots in tubing or liner, well screen or other tortuous flow path assemblies. Valves or other metering devices may control inflow and/or outflow from the flow control devices 200.
Solid wall lined portions 201 of the horizontal lengths of the wells 111, 112, 113 may prevent fluid communication from inside the wells 111, 112, 113 to the formation. The lined portions 201 without fluid communication to the formation may separate the flow control devices 200 from one another along the horizontal lengths of the wells 111, 112, 113. In some embodiments, the flow control devices 200 of the first well 111 align between the flow control devices 200 of the second well 112 and across from the lined portions 201 of the second well 112. The flow control devices 200 of the third well 113 may also align across from the flow control devices 200 of the first well 111.
In some embodiments, the conditioning fluid as referred to herein and used in the all injection cycle can be any fluid capable of reducing viscosity or increasing mobility of the hydrocarbons by dissolving into the hydrocarbons and/or transferring heat to the hydrocarbons. The conditioning fluid may however not rely on any thermal application and may consist of only a solvent for the hydrocarbons. Economics may not support applying heat to the hydrocarbons with the conditioning fluid due to factors such thickness or extent of the formation.
For example, the solvent may be a lighter hydrocarbon than contained in the formation and may have 1 to 20 carbon atoms (C1-C20) or 1 to 4 carbon atoms (C1-C4) per molecule, or any mixture thereof. Examples of C1 to C4 hydrocarbon solvents include methane, ethane, propane and/or butane. The hydrocarbon solvent used as the conditioning fluid can be introduced into the formation as a gas or as a liquid regardless of its phase under reservoir conditions.
Composition of the conditioning fluid may also transition during any injection operation disclosed herein. For example, the all injection cycle may first utilize a liquid hydrocarbon solvent under reservoir conditions, such as diesel, for the conditioning fluid followed by a gaseous solvent under reservoir conditions, such as a mix of propane and carbon dioxide, for the conditioning fluid. Injecting the propane as a liquid may further provide drive energy upon flashing to gas in the formation to facilitate subsequent recovery.
The flow control devices 200 permit controlled inflow of the hydrocarbons into the wells 111, 112, 113 at where dispersed along the horizontal lengths of the wells 111, 112, 113. Processing the hydrocarbons produced to surface during the all production cycle may separate out the conditioning fluid for recycle. In some embodiments, cycling during additional time intervals between the all injection cycle shown in
Examples of the displacement fluid include gases or liquids capable of pushing the hydrocarbons through the formation. The displacement fluid may in some embodiments also facilitate recovery by further decreasing viscosity of the hydrocarbons in the formation. The displacement fluid may contain like constituents as the conditioning fluid described herein and which may likewise include any constituent described herein for use as the displacement fluid.
For some embodiments, the displacement fluid includes any combination of gaseous or liquid solvents for the hydrocarbons, water, steam, emulsifiers (e.g., surfactants, alkalis, polymers), air, oxygen and carbon dioxide. Heating any of the fluids used for the displacement fluid enables heat transfer to the hydrocarbons for viscosity reduction. Injection of combustibles, such as air or oxygen, as the displacement fluid enables starting in situ combustion during the displacement operation for recovery, which depends on the fluid communication being established between the wells 111, 112, 113.
In closing, it should be noted that the discussion of any reference is not an admission that it is prior art to the present invention, especially any reference that may have a publication date after the priority date of this application. At the same time, each and every claim below is hereby incorporated into this detailed description or specification as an additional embodiment of the present invention.
Although the systems and processes described herein have been described in detail, it should be understood that various changes, substitutions, and alterations can be made without departing from the spirit and scope of the invention as defined by the following claims. 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, while the description, abstract and drawings are not to be used to limit the scope of the invention. The invention is specifically intended to be as broad as the claims below and their equivalents.
This application is a non-provisional application which claims benefit under 35 USC §119(e) to U.S. Provisional Application Ser. No. 61/683,373 filed Aug. 15, 2012, entitled “PRECONDITIONING FOR BITUMEN DISPLACEMENT,” which is incorporated herein in its entirety.
Number | Date | Country | |
---|---|---|---|
61683373 | Aug 2012 | US |