3D mechanical modeling and analysis of influencing factors on fracture breakdown pressure in dual horizontal well intensive hydraulic fracturing

Horizontal well intensive fracturing is a critical technology used to stimulate unconventional oil and gas reservoirs. Accurate prediction of wellbore breakdown pressure is conducive to optimal fracturing design and improvement of the reservoir stimulation effect. In this work, the three-dimensional displacement discontinuity method (DDM) is used to characterize fracture deformation and fracture closure after the pumping pressure relief. The influences of key parameters such as the minimum horizontal principal stress, fracture spacing, the Young's modulus, the Poisson's ratio and pumping pressure on the breakdown pressure are analyzed. The results show that, assuming that the fracture half-length is a , the breakdown pressure outside the fracture surface area increases significantly within 2 a in the direction of the minimum horizontal principal stress and a in the directions of the vertical stress and maximum horizontal principal stress before pressure relief. The breakdown pressure of the modified zipper-type fracturing in the later stage is lower. When the fracture spacing is small, the fracture breakdown pressure decreases after the modified zipper-type fracturing of two horizontal wells. The fracture breakdown pressure of the first fractured well reaches a maximum when the fracture spacing is a – 1.5a, and the breakdown pressure decreases with increasing well spacing.