Research on the law of fracture closure in shale gas reservoirs under gas invasion conditions

There are multiple pressure formations in the process of shale gas drilling, which are prone to overflow accidents, thereby increasing the nonproductive time and drilling costs. In order to study the law of fracture closure under gas intrusion, a fracture deformation model considering the elastoplastic deformation of asperities is established in this study. The model realizes the coupling of the wellbore multiphase flow model and the bottom hole pressure boundary. The calculation of fracture deformation under load conditions is carried out, and the numerical calculation results are compared with the test data in the reference, and the error is 8.6%. In addition, the influence degree of factors such as fracture width, fracture roughness, fracture length and fracture inclination angle was analyzed based on the actual shale gas well data. The results show that fractures with large fracture width, long radius and low roughness have larger fracture deformation and pressure drop, and the effect of fracture inclination is relatively small. After taking control measures to restore the original bottom hole pressure, the fracture still has a deformation of 1.67%, which reduces the permeability in the near-wellbore zone. Therefore, with the continuous gas invasion, the width of the fracture is in a state of fluctuation, which will affect the later fracturing and production.