Study on Multiscale Fluid–Solid Coupling Theoretical Model and Productivity Analysis of Horizontal Well in Shale Gas Reservoirs

In order to study the productivity dynamic evolution laws of shale gas horizontal well, a multiscale seepage theoretical model considering the fluid–solid coupling effect is proposed first in this paper, which introduces an anisotropic matrix permeability model that comprehensively considers multiple flow regimes and an artificial hydraulic fracture conductivity model that considers proppant deformation and embedment. Then the reliability of the theoretical model is verified by the field production data obtained from the Marcellus shale. Based on the established productivity model, the evolution laws of pore pressure and permeability in different areas of the reservoir with different production periods are studied first, and then the shale gas production rate and cumulative production under different physical mechanisms, different shale gas flow regimes, and different reservoir parameters are quantified and analyzed. The simulation results show that the pore pressure in the hydraulic fracture area decreases rapidly at the initial stage of production, resulting in large deformation, and the fracture conductivity tends to be stable gradually at the later stage of production. The desorption effect will increase shale gas production, while the stress sensitivity is just the opposite. When only real gas flow is considered, the gas cumulative production is the highest. The fluid–solid coupling of hydraulic fractures has a great impact on the production, while the fluid–solid coupling in the matrix area has a small impact on the production, which can be ignored if appropriate. During the sensitivity analysis of reservoir parameters, it is observed that the influence of parameters of hydraulic fractures on production is much higher than that of matrix regional parameters. During the production process, these influencing factors can be adjusted according to the change of production data to achieve the optimization of shale gas production. In a word, the new model proposed in this paper provides a more accurate method to estimate the impact of multiple physical mechanisms, especially the fluid–solid coupling effect, on shale gas production compared with the existing model. The research results of this study can provide some reference and guidance for the dynamic prediction of shale gas production and optimization of production parameters.