An integrated reservoir-geomechanics-fracture model is implemented in a deep shale gas reservoir in the Sichuan Basin, Western China, to optimize the parent–child well spacing under various complex natural fracture settings. The integrated multiphysics model employs an embedded discrete fracture model to characterize fluid flow through complex natural and hydraulic fractures, a finite element method geomechanics model to predict the 3D spatiotemporal stress changes, and a displacement discontinuity method hydraulic fracture model to simulate the multicluster fracture propagation under the depletion-induced heterogeneous stress field. Field case studies on two complex natural fracture patterns (i.e., orthogonal and clustered natural fractures) show that (a) the orientation change of maximum horizontal stress (SHmax) is negligible since the target shale gas reservoir is highly stressed and under large horizontal stress contrast; (b) the decrease in minimum horizontal stress (Shmin) over the stimulated reservoir volume is about 30–50% of pore pressure drop due to the rapid pressure depletion; (c) decreasing the parent–child horizontal/vertical spacing or elongating the production time aggravates the asymmetry growth of child-well fractures in either natural fracture pattern; (d) the parent and child wells are suggested to space farther under the clustered natural fracture pattern to avoid undesirable interwell fracture interference caused by the irregular localized stress sink. This work delivers a comprehensive understanding of the geomechanics consequences under different natural fracture settings and provides practical guidance on infill operations in layered formations of the Sichuan Basin.
Article Highlights: An integrated reservoir-geomechanics-fracture model is employed to optimize the parent–child well spacing in a multilayer deep shale gas reservoir with complex natural fracturesThe complex fracture network, in situ stress change, and multicluster fracture propagation are simulated by EDFM, FEM geomechanics model, and DDM hydraulic fracture model, respectivelyThe impacts of orthogonal and clustered natural fractures on spatiotemporal stress evolution and parent–child well layout are investigated based on actual field datasetsThe parent–child well spacing is optimized by incorporating geomechanics responses in addition to fluid-flow simulation to provide hands-on guidance for the Sichuan Basin