The development of waterflood-induced fractures (WIFs) during water injection is critically governed by the adopted injection-production strategy, which ultimately determines the resulting fracture network morphology. Current understanding of how to optimize these parameters to steer fracture propagation remains limited. To resolve these challenges, this study develops a coupled hydraulic-mechanical-damage model that incorporates reservoir heterogeneity along with the coupled processes of fluid seepage, rock deformation, and damage evolution. The model is validated against an analytical solution. Utilizing a representative one-injection-two-production numerical model, the study simulates multiphysical field interactions during waterflooding and systematically analyzes the impact of injection and production rates on WIFs propagation. Simulation results reveal that increasing the injection rate predominantly drives the longitudinal propagation of primary fractures. In contrast, the production rate exhibits a stage-dependent dual effect. It inhibits fracture propagation during the middle stage but promotes it in the later stage by strengthening the pressure gradient and activating natural fractures. Based on these mechanisms, a dynamic injection-production strategy is proposed, initiated with a high-injection and low-production regime to drive fracture length, then switching to a low-injection and high-production regime to enhance network complexity. Furthermore, the waterflooding efficiency index (WEI) is introduced as a novel metric for quantitative evaluation. The proposed dynamic strategy achieves a higher WEI compared to a conventional uniform strategy, thus validating its efficacy in enlarging the effectively swept area. This study provides critical insights into the propagation mechanisms of WIFs controlled by injection and production parameters, offering a scientific basis for designing efficient development strategies in fractured tight reservoirs.
Weng et al. (Sun,) studied this question.