Fluid–Solid Coupled Simulation of Fractured Horizontal Wells in Deep Shale Gas Reservoirs

Multiscale gas storage and transportation spaces exist in shale gas reservoirs. For deep shale gas, the stress changes caused by the variation of pore pressure become more significant; thus, it is necessary to carefully consider the impact of fluid–solid coupling in the production models. In this work, a fully fluid–solid coupling model, which systematically considers the impact of pore space changes due to applied stresses and gas desorption, for fractured horizontal wells is developed. Multiple flow mechanisms, including the Langmuir isothermal adsorption/desorption, Knudsen diffusion, surface diffusion, and slippage effect, are also integrated using the finite element solver in COMSOL Multiphysics. The model is validated against both analytical solutions and field production data. The effects of different parameters, such as geomechanical, geological, and hydraulic fracture properties, on production are analyzed. The results show that although the increment in effective stress reduces porosity and permeability, the consideration of Knudsen diffusion and surface diffusion leads to an enhancement in the matrix permeability. If the fluid–solid coupling effect is not considered, the cumulative gas production could be overestimated, while the coupling with complex flow mechanisms can enhance the total production. Among geological parameters, initial reservoir pressure and matrix porosity play the most important role in production. Asymmetric hydraulic fracture geometries yield the best production performance. Moreover, the identified stress reversal behavior outside the fractured zone provides theoretical guidance for determining the timing of refracturing and infill wells.