Investigation on Well Interferences of Infill Well Fracturing in Shale Gas Reservoirs Across Sichuan Basin

The development of infill wells have gained significant traction in enhancing shale gas recovery in the Sichuan Basin. During the development of infill wells, the production of the parent wells leads to changes in in-situ stress, which in turn affects the fracture morphology of the infill well, resulting in frac-hits. These frac-hits are commonly considered a potential hazard to the adjacent infill well production and wellbore. In this study, a comprehensive flow-geomechanics coupling model has been developed to address this challenge. The model incorporates the processes of parent well fracturing and production, evolution of in-situ stress after production, and infill well fracturing and production. This study discusses four cases in the Sichuan Basin, each highlighting intriguing field phenomena. The first case focuses on an infill well situated in the same layer, while the second case pertains to a three-layers infill wells pad. The third case delves into the phenomenon of frac-hits in deep shale gas reservoirs (3800 m), while the final case explores the effect of high-steep structures in the fracturing process. By utilizing this integrated model and field data, the mechanisms underlying these phenomena are observed. The results indicate that: (i) The ‘microseismic events barrier’ (MSEB) effect caused by stress shadow has been reported and the main reasons have been analyzed. (ii) The range of stress shadow is critical to the deployment of multi-layers infill well pattern, the influence range in both horizontal and vertical directions is related to the size of hydraulic fractures. (iii) In deep shale gas reservoir, high stress and the development of natural fracture zones are the main reasons of frac-hit and the fracturing sequence can exacerbate this phenomenon. (iv) The high formation dip in the high-steep structural zone will restrict the propagation of hydraulic fractures in the horizontal direction. Through this research, valuable insights into the behavior of infill wells in the Sichuan Basin have been obtained, shedding light on the challenges and opportunities associated with maximizing shale gas recovery in this region.