Multi-Fracture Growth Law for Temporary Plugging and Diversion Fracturing of Horizontal Well with Multiple Clusters in Shale Reservoir

Temporary plugging and diversion fracturing (TPDF) is a common method to increase production and efficiency in shale gas reservoirs, but the growth law of diversion fractures and the temporary plugging mechanism are still unclear, which restricts the further optimization of temporary plugging fracturing schemes. Therefore, in this study, a series of simulation experiments of TPDF in a horizontal well with multi-clusters were carried out for the Longmaxi Shale outcrop by using a large true triaxial fracturing system. The laboratory method of "inner-fracture + inner-segment" TPDF with multiple clusters of perforation in horizontal wells was proposed, and the fracture initiation law and control factors, including the number of clusters and the method of perforating, were investigated. The experimental results show that the peak pressures of inner-fracture temporary plugging (IFTP) and inner-segment temporary plugging (ISTP) stages are higher, and the number of diversion fractures and the overall complexity of hydraulic fractures (HFs) are higher when the number of perforation clusters is five. The peak pressures of IFTP and ISTP do not increase significantly under the fixed-face perforating condition compared with the helical perforating, but the pressure profile fluctuates more frequently, the overall HF morphology is more complex, and the number of diversion fractures and transverse hydraulic fractures (THFs) is higher. In addition, the diversion of multi-fractures corresponds to a stage of frequent fluctuations in the wellhead pressure, during which the pressure reaches the peak and drops sharply, indicating the generation of diversion fractures with larger fracture widths that grow toward the surface of the rock sample. The results of the study provide a theoretical basis for the design of TPDF schemes in the laminar-rich Longmaxi Formation shale reservoir.