Patent ID: 9556719
Date: 2017-01-31
CPC Classifications: E21B

Claim:
1. A method for recovering hydrocarbon gas through a horizontal wellbore from a shale formation section which, prior to being heated from combustion of oxidizer, comprises hydrocarbon gas with substantially no kerogen or heavy oils having an API gravity of less than 25 degrees, comprising: (a) injecting oxidizer through the horizontal wellbore and into the shale formation section, wherein the shale formation section includes a shale matrix having a structure with substantially no kerogen or heavy oils with an API gravity of less than 25 degrees, a primary fracture formed by a previous hydraulic fracturing operation, residual hydrocarbon gas in the primary fracture, and pores that contain hydrocarbon gas; (b) reacting a portion of the oxidizer with residual hydrocarbon gas in the primary fracture to form a combustion product and heat, wherein the residual hydrocarbon gas is hydrocarbon gas remaining in the primary fracture after a previous hydraulic fracturing operation; (c) transferring the heat through the shale matrix to a first and a second pore that each contain hydrocarbon gas; (d) rupturing the first pore by heating hydrocarbon gas contained in the first pore and thereby raising the pressure of the hydrocarbon gas being heated in the first pore to a level sufficient to rupture the first pore, weaken the structure of the shale matrix, and form a first micro-fracture in the shale matrix, wherein the first micro-fracture is connected to the primary fracture and contains hydrocarbon gas that is consumed by combustion, and (e) rupturing the second pore by heating hydrocarbon gas contained in the second pore and thereby raising the pressure of the hydrocarbon gas being heated in the second pore to a level sufficient to rupture the second pore, weaken the structure of the shale matrix, and form a second micro-fracture in the shale matrix, wherein the second micro-fracture is not connected to the primary fracture and contains hydrocarbon gas that is not consumed by combustion; (f) injecting hydraulic fracturing fluid through the horizontal wellbore and into the primary fracture to form one or more macro-fractures in the shale matrix having a weakened structure by expanding or coalescing the first and second micro-fractures during the injecting of the hydraulic fracturing fluid; and (g) recovering hydrocarbon gas that passes through the one or more macro-fractures and into the horizontal wellbore.