Numerical Simulation of Complex Fracture Propagation in Shallow Shale Gas Fracturing in Zhaotong

The main burial depth of the shallow shale gas field in Zhaotong is 1000-2200 m. The formation pressure coefficient is low, making the benefit development challenging. Hydraulic fracturing technology remains the only stimulation measure. However, there is no prior experience of large-scale development of medium and shallow shale reservoirs in China for reference. Therefore, there is still room for optimizing hydraulic fracturing parameters. In consideration of the geological and engineering characteristics, such as natural fracture development, small horizontal stress differences, and large perforation cluster numbers of the main stimulation, a numerical simulation of complex fracture propagation in shallow shale gas fracturing in Zhaotong was conducted. The displacement discontinuity method was employed, with the interaction mode of natural and hydraulic fractures considered. Based on the fracture flow equation, fracture width equation, and mass balance equation, the mathematical model of complex fracture propagation was derived. Based on the model, construction parameters were optimized according to the actual geological characteristics of shallow shale gas in Zhaotong. It was determined that natural fractures and perforation cluster numbers were the main factors affecting the stimulated reservoir volume (SRV). At the same time, through the temporary plugging numerical simulation, it is clarified that temporary plugging is conducive to improving the fracture opening efficiency, and the location, timing and times for temporary plugging have obvious effects on the temporary plugging effect. The simulation results were compared with on-site test results, demonstrating that the optimized fracturing measures increased daily single gas production by 30.3%. Consequently, this study provides valuable insights for the subsequent fracturing treatment of shallow shale gas in Zhaotong.