The impact of geomechanics and perforations on hydraulic fracture initiation and complexity in deep shale reservoirs

In view of the scientific problem of non-uniform initiation of hydraulic fracturing perforation clusters in unconventional anisotropic reservoirs, this paper considers the anisotropy of weak plane and the superposition of stress concentration effect of perforation hole and wellbore, and establishes the stress model of arbitrary directional hole and perforation hole and the analytical model of hydraulic fracture initiation morphology prediction. The initiation conditions of vertical and horizontal fractures are studied. the mechanical analysis of two wells with the largest difference in production in Luobu block is carried out. The results show that the stress distribution around the perforation hole has a significant influence on the fracture initiation pressure, which affects the geometry of the fracture near the wellbore. In well Y1, which is arranged along the direction of the minimum horizontal principal stress and is mainly in the stress state of the strike-slip partial normal fault, the main mechanical reason for the absence of gas-liquid is that the two stress concentrations of the borehole and the perforation channel lead to the reversal of the horizontal principal stress of the in-situ stress field near the well, and the stress state becomes reverse fault. The near well is mainly horizontal fracture, and the gas-liquid migration channel is blocked. In the Y2 well, which is in the stress state of the strike-slip normal fault, the stress state becomes a strike-slip reverse fault after two stress sets, and the vertical fracture initiation range accounts for more than 75%. The connectivity of the near-well fracture channel is good, which is helpful for the migration of gas and liquid in the reservoir. This study offers insights for the optimal design of perforation holes in hydraulic fracturing, providing information on the minimum fracture initiation pressure and the optimal perforation direction for the wellbore-reservoir connecting channel in practical field applications.