Influencing factors and prevention optimization of shallow shale gas inter-well frac-hits

The Zhaotong shallow shale gas field is the first pilot demonstration area in China for medium to shallow shale gas development, with main burial depths ranging from 1 000 to 2 200 m. Due to asynchronous production and infrastructure construction and a small horizontal stress difference in the regional fault system, inter-well interference frequently occurs during the fracturing of new wells. This presents a series of problems such as extensive frac-hits and difficulty in restoring production. The frac-hits between fractured wells and producing wells are mainly characterized by fast response, difficult production recovery, and multiple occurrences. Statistical analysis of affected wells showed that the longer the production time, the lower the recovery rates after the implementation of frac-hits control measures. To address these challenges, it is imperative to analyze the influencing factors of inter-well frac-hits and propose preventive measures. The study comprehensively reviewed the dynamic and static parameters under the engineering and geological conditions from 32 wells experiencing frac-hits in the Zhaotong shallow shale gas field. A random forest model was trained to evaluate the influence of geological and engineering parameters on frac-fits. The main controlling factors were identified as well spacing, construction intensity, and the production time of the parent well. Numerical simulations suggested an optimal parent-child well spacing of 450 m. Orthogonal design simulations revealed that parent wells consistently suffered negative interference after experiencing frac-hits, with the interference ratio increasing from 6.3% to 35% as the production time extended. When the parent-child well spacing exceeded 400 m within the first year of parent well production, child wells experienced positive interference, and the interference degree ranging from 2.5% to 8.6% as well spacing increased. The proposed well spacing optimization strategy supports well location deployment and fracturing parameter optimization in the Zhaotong shallow shale gas field, validating the research results.