Hydraulic-Mechanical Coupling-Driven In Situ Stress Field Evolution in Injection-Production Well Patterns With Artificial Fractures

Abstract

Based on the theory of porous media elasticity and the mechanisms of hydraulic-mechanical coupling, a fully coupled mathematical model for porous media deformation and fluid flow was established, incorporating a square inverted nine-spot well pattern with artificial fractures. The finite element method was employed for numerical solution, and the model′s accuracy was verified through comparison with the classical Terzaghi′s poroelastic problem. Numerical simulations were conducted to investigate the evolution of the in situ stress field during the development of injection-production well groups, exploring the optimal timing for refracturing and the influence of engineering-geological parameters on the stress field. Orthogonal experimental analysis was introduced to more precisely quantify the impact of various factors on the stress reorientation range in injection-production well groups. The results demonstrate that during production, reservoir stress reorientation is primarily governed by pore pressure and expands over time, with the optimal reorientation timing occurring when pore pressure stabilizes. Different fracturing conditions significantly alter the stress reorientation angle and range, thereby affecting the stress distribution among wells. The stress reorientation range exhibits a positive correlation with fracture penetration ratio but a negative correlation with initial stress ratio, Poisson′s ratio, porosity, and permeability. Among these factors, the initial horizontal principal stress ratio, fracture penetration ratio, and reservoir permeability exert the most pronounced influence, whereas the elastic modulus has minimal impact.