Two-Way Coupled Flow and Geomechanics Simulation with Advanced Dual-Porosity and Dual-Permeability and Local Grid Refinement for Shale Primary Depletion

This paper represents a new two-way coupled flow and geomechanical simulation model that utilizes an Advanced Dual Porosity Dual Permeability (A-DPDK) model with local grid refinement (LGR). A hydraulic fracture's conductivity is strongly dependent on the effective stress on fracture face. During production, increased effective stress could cause proppant embedment, crushing, and fracture closure. Coupled flow and geomechanical simulation is critical to capture the fracture conductivity changes with stress and perform accurate production forecast. The geomechanical problem with the DPDK can be solved with the constitutive equations for stress and porosity of multiple porosity systems. A fractured reservoir contains different regions in the fracture domain, for example, propped, unpropped, and natural fractures which have different mechanical properties. Our proposed model mathematically represents mapping of mechanical properties in different regions of fracture and matrix domains. In addition, we showed the mapping between a LGR flow system and a non-LGR geomechanical system. We demonstrated a realistic fracture geometry with the A-DPDK LGR system. We validated the numerical convergence of the A-DPDK with LGR by performing grid size sensitivity tests in flow and mechanical grids. The proposed simulation model was applied to oil production from a shale and tight (S&T) reservoir. The proposed simulation approach can model total stress update near fractures more realistically. The new stress and pressure results obtained from the integrated flow and geomechanics workflow allowed us to incorporate stress impact from the depletion of a different bench and the resulting fracture azimuth change. The combination of a LGR flow system and a non-LGR geomechanical system supports reasonable computational time even with two-way coupling simulation, which encourages us to adopt the new simulation approach for modeling oil production and evaluating stress change.