Dynamic evolution mechanisms of induced stresses in hydraulically fractured wells: Incorporating real gas characteristics

Abstract

The spatiotemporal evolution mechanisms of induced stresses stemming from hydraulic fracturing and production, particularly in the context of actual gas extraction, remain poorly understood. Therefore, a novel simulation method for induced stress due to real gas production is proposed, integrating the Redlich-Kwong equation of state, the Lee-Gonzalez-Eakin correlation, and fluid-solid coupling theory. Furthermore, an integrated simulation of hydraulic fracturing and gas recovery is also achieved. This approach comprehensively accounts for the nonlinear compressibility and viscosity characteristics of real gases under high-pressure reservoir environments, while simultaneously incorporating the stress-dependent variations in reservoir porosity and permeability. We explore fracturing- and production-induced disturbances such as stress redistribution, displacement, and rotation angle, and assess the impact of fluid types. This work reveals that: (a) Hydraulic fracturing triggers the deflection zones comprising an elliptical main reversal zone and a large fan-shaped reorientation zone. In contrast, the production-induced deflection zones additionally feature a circular-arc-shaped secondary reversal zone at the leading edge of fracture tip. (b) Gas extraction induces a significantly larger deflection zone than oil recovery over the same production period. This disparity arises from the smaller dimensionless time of oil production relative to gas production. Nevertheless, both hydrocarbon recovery processes exhibit remarkably similar distribution of the deflection zone, a consequence of their identical dimensionless stress deviators. Our research offers a reliable simulation approach for induced stress evolution during hydrocarbon exploitation, which will provide the quantitative basis for optimizing the design of subsequent stimulations, and preventing potential engineering and geological disasters.