Numerical simulation of fracturing and shut-in integration of horizontal Wells in shale reservoirs: A case study of horizontal Wells in Qingcheng Oilfield

Effectively leveraging the imbibition effect between fractures and the matrix to enhance the mobilization of crude oil within the matrix is a key approach to improving the development efficiency of tight reservoirs. The study, taking the Qingcheng HFTS project as the backdrop and considering the imbibition effect and flow in complex fracture systems, established an integrated numerical model for fracturing and well shut-in operations. It identified the main imbibition mechanisms of Qingcheng shale oil, investigated the characteristics of pressure and saturation distribution during the reservoir fracturing and well shut-in process under complex fracture morphologies, and proposed an optimization method for well shut-in. The research results indicate that the primary imbibition mechanism of Qingcheng shale oil is capillary force; after 30 days of well shut-in, the pressure diffuses to a distance of 65 meters on both sides, which can increase the formation energy across the entire well, with the energy-increasing area reaching 486,000 square meters. In some stages with cluster spacing that is too small, pressure diffusion is restricted, necessitating an appropriate extension of the shut-in time to avoid sand production from the formation and uneven fluid production during later stages of extraction.