A Hybrid Semianalytical Model for Studying the Two-Phase Flow Behavior of Multifractured Horizontal Wells in Gas Reservoirs

Summary After fracturing, the retained fracturing fluid generally induces gas/water two-phase flow in the vicinity of the fracture, while the far-field region remains dominated by single-phase gas flow. Numerical solutions for the outer single-phase region require extensive grid discretization and are computationally expensive, whereas analytical solutions fail to accurately capture the complex two-phase flow behavior. To solve this issue, we propose a hybrid semianalytical model for multifractured horizontal wells to investigate the transient flow behavior during production. Specifically, the two-phase flow in the vicinity of the fracture is numerically characterized using the finite difference method, while the gas flow in the surrounding single-phase region is analytically described by Green’s function in the Laplace domain. The proposed model captures complex two-phase flow behaviors while maintaining high computational efficiency. With the aid of Blasingame decline curves, five flow regimes are identified: early bilinear flow, early linear flow, pseudoboundary-dominated flow, intermediate linear flow, and boundary-dominated flow. Subsequently, the sensitivity analysis of key parameters is conducted, and the calculation results show that a higher fracture conductivity leads to a more pronounced half-slope behavior on the Blasingame type curve. A threshold value of fracture conductivity is observed (10 md·m in this study), beyond which further increases exert negligible influence on cumulative production. The initial water saturation significantly influences the transient flow behavior throughout the production period, with the higher water saturation leading to reduced cumulative gas production. The increase in fracture length significantly prolongs the duration of the early linear flow regime.