Multi-Well Pressure Interference and Gas Channeling Control in W Shale Gas Reservoir Based on Numerical Simulation

Abstract

Well interference has drawn great attention in the development of shale gas reservoirs. In the W shale gas reservoir, well interference increased from 27% to 63% between 2016 and 2019, but the gas production recovery of parent wells was only about 40% between 2018 and 2019. Therefore, the mechanism and influencing factor of well interference degree were analyzed in this study. A numerical model of the W shale gas reservoir was developed for history matching, and the mechanisms of well interference and production recovery were analyzed. Sensitivity analysis about the effect of different parameters on well interference was carried out. Furthermore, the feasibility and effectiveness of gas injection pressure boosting to prevent interference were demonstrated. The results show that the main causes of inter-well interference are: the reservoir energy of the parent well before hydraulic fractures of the child well, well spacing, the fracture connection, etc. The fracture could open under high pressure causing fracturing fluid to flow in, while fracture closure happens under low pressure and the influence on the two-phase seepage in the fracture becomes more serious. The combination of liquid phase retention and fracture closure comprehensively affects the gas phase flow capacity in fractures. Gas injection pressure boosting can effectively prevent fracturing fluids flowing through connected fractures. Before the child well hydraulic fracturing, gas injection and pressurization in the parent well could reduce the stress difference and decrease the degree of well interference. The field case indicates that gas channeling could be effectively prevented through parent well gas injection pressurization.