Thermal hydrocarbon recovery method using shock cycling fluid stimulation

Abstract

A thermal hydrocarbon recovery method comprising cycling high pressure fluid injection for a period of time followed by low pressure fluid injection for a period of time, the high pressure injection primarily to dilate and enhance reservoir porosity / permeability and improve the subsequent low pressure fluid injectivity. The method is particularly useful for recovering heavy and extra heavy hydrocarbons from tight formations and / or low vertical permeability reservoirs under viscosity reduction and gravity drainage methods. This method is believed to be applicable for recovering heavy or extra heavy oil from reservoirs with geological risk associated with cap rock integrity.

Description

CROSS-REFERENCE TO RELATED APPLICATION[0001]This application claims the benefit of and priority to U.S. Provisional Patent Application Ser. No. 62 / 098,607, filed Dec. 31, 2014, entitled “Thermal Hydrocarbon Recovery Method Using Shock Cycling Fluid Stimulation,” the contents of which are incorporated herein in its entirety for all purposes.FIELD OF THE INVENTION[0002]The present invention relates to thermal hydrocarbon recovery techniques, and more particularly to methods for extracting heavy oil resources from tight reservoirs.BACKGROUND OF THE INVENTION[0003]In the art of hydrocarbon recovery, it is known to use thermal recovery methods for producing heavy oil / bitumen from subsurface reservoirs. For example, steam-based methods such as cyclic steam stimulation (CSS) and steam assisted gravity drainage (SAGD) are commonly used for in-situ recovery operations. While surface mining of bitumen is employed in appropriate settings, the majority of reservoirs are located at depths where ...

AI Technical Summary

Benefits of technology

The present invention provides a method for extracting oil from underground using two different fluids, with the first fluid (often a high pressure fluid) being injected for a short time to dilate the rock and improve the subsequent injection of the second fluid (often steam). The brief high pressure injection creates small cracks in the rock, making it easier for the second fluid (often steam) to flow through and extract the oil. This method helps to improve the efficiency of oil extraction from underground reservoirs.

Problems solved by technology

While surface mining of bitumen is employed in appropriate settings, the majority of reservoirs are located at depths where surface mining is not economically or technically feasible, and thus in-situ recovery techniques are conventionally employed.

However, in some geological settings, the cap rock overlying the reservoir is of insufficient integrity to support a prolonged high pressure injection regime.

As a result of a low minimum stress gradient in some of the reservoirs, where capping shale is in a vertical fracture regime, high pressure fluid injection is not an alternative due to the risk of cap rock failure.

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