Effect of Pressure Decline Rate on Horizontal Well Performance in Transitional Shale Gas Reservoirs

Technical advances in horizontal drilling and hydraulic fracturing have been key drivers enabling the economic production of shale gas. While substantial efforts have been devoted to optimizing well productivity, the effect of the early pressure decline rate on horizontal well performance remains poorly understood in transitional shale gas reservoirs, which exhibit significant stress sensitivity. To address this, a multiscale flow model that integrates the Embedded Discrete Fracture Model (EDFM) with a geomechanical stress-sensitivity model was developed. This model describes the flow through matrix pores, bedding fractures, and hydraulic fractures and was validated against a field case. The results indicate that rapid fluid drainage during the early production stage creates a larger pressure drainage area. Specifically, a depletion rate of 0.2 MPa/d yields a 10% production increase over a rate of 0.05 MPa/d. However, stress sensitivity reduces overall production by approximately 20% while the bedding fracture connectivity can improve it by about 5%. For well X1H, the current production status suggests that gas and water are likely trapped or ‘blocked’ within the fractures; flow conductivity enhancement is recommended. For adjacent wells with a stress sensitivity coefficient exceeding 0.8, flow-restricted zones may extend into the matrix pores; stress sensitivity should be avoided.