Reshaping the trajectory of simultaneously-stimulated hydraulic fractures with temporary plugging agents: a DEM simulation perspective

Temporary plugging technique is an effective way to promote the uniformity and complexity of the hydraulic fractures in unconventional hydrocarbon reservoirs. The plugging agent form low-permeability zones and the plugging effect inhibits the propagation of the opened fracture. However, the coupling of the agent migration along the fracture and fracture morphology evolution is rarely and comprehensively considered base on physical reality. In this study, a plugging model by calculating the local conductivity loss of the fracture and the agent migration behavior is developed to establish a discrete element model on multi-cluster fracturing with temporary plugging technique. The dynamic distributions of agent concentration, fluid pressure, fracture morphology, and the influences of the injection concentration and agent size are systematically analyzed to elucidate the formation mechanism of the plugging layer and its effect on competitive fracture propagation. The research results show that: (1) fracturing fluid is prevented from reaching the fracture tip, leading to the formation of three distinct segments within the fracture: a plugging zone near the fluid entrance, a pure fluid zone in the middle section, and a dry fracture zone at the tip. (2) Higher injection concentration increases the pressure drop along the fracture and thus raises injection pressure. For agent size, a critical threshold appears in the injection-pressure response, and finer agents promote more uniform fracture lengths and fluid distribution. (3) An analytical model quantifies plugging ability and plugging time. Plugging ability increases with agent size, while plugging time increases with agent size but decreases with concentration. Earlier and stronger plugging layers promote fracture initiation from more perforation clusters.