Stress Interference Mechanisms in Hydraulic Fracturing and Impacts on Multiwell Fracturing of Tight Reservoirs

The increasing application of pad drilling technology in unconventional reservoirs has significantly enhanced development efficiency and reduced operational costs. However, as well spacing decreases, hydraulic fracturing interference between wells has emerged as a critical factor affecting fracture geometry, propagation, and production performance. Despite the adoption of advanced multiwell fracturing techniques, such as zipper fracturing (ZF) and modified ZF (MZF), the mechanisms of stress interference and their influence on fracture propagation remain poorly understood. This study employs the Extended Finite Element Method coupled with the Cohesive Zone Model (XFEM-CZM) to analyze the effects of stress interference and fracture geometry variations under different fracturing scenarios. The results reveal that when the fracture spacing is large, the stress interference induced by two fractures conforms to the principle of superposition. However, at smaller fracture spacings, stress interference significantly impacts the propagation process and geometry of subsequent fractures, resulting in nonlinear stress interference characteristics. Using the M block in Xinjiang as the study area, this research further analyzes the effects of ZF, MZF, and different fracturing sequences on fracture geometry in multiwell systems. The findings demonstrate that MZF generates longer fractures while ZF exhibits more symmetric propagation characteristics. Moreover, combining MZF with an optimized fracturing sequence maximizes the stimulated reservoir volume (SRV), minimizes casing deformation, and avoids frac-hit. These results provide theoretical guidance and practical insights for optimizing hydraulic fracturing designs in multiwell pads within tight reservoirs.