Abstract: Aiming at the difficulty of productivity prediction in shale gas reservoirs due to the influence of two-phase complex flow and fluid-solid coupling, the seepage field is divided into the primary modified zone, the secondary modified zone and the unmodified zone, and a multi-scale gas-water two-phase flow-fluid-solid coupling mathematical model is established by combining the multi-fluid unified transport model and the equivalent continuous non-uniform medium physical model, and the mathematical model is programmed and solved by gridless generalized finite difference. The results of the study show that the gridless generalized finite difference method can adapt to different computational domains and avoid the arithmetic instability caused by the coupling of traditional difference grids with unstructured grids; the propagation of the pressure drop leading edge in the unmodified zone is only about 20 m, and the solid displacement mainly occurs in the junction area between the secondary modified and unmodified zones; neglecting the influence of the stress field, the gas production is significantly overestimated at the early stage of gas well production, and this influence gradually decreases at the later stage of production; the shale gas reservoirs with low initial water saturation are more beneficial for development, focusing on water saturation during reservoir selection. The study results have important guidance for future numerical simulations of fluid-solid coupling and unconventional oil and gas reservoir capacity prediction.

Key words: shale gas reservoir, gridless method, numerical simulation, multi-scale flow, fluid-solid coupling