Mechanistic study on the effect of seepage force on fracture propagation behavior in multi-cluster fracturing of horizontal wells

Abstract

During multi-cluster fracturing of horizontal wells, low-viscosity fracturing fluid permeates extensively along the fracture walls into the rock pores, exerting seepage forces on the rock skeleton. However, the mechanism of how seepage forces influence multi-cluster fracture propagation behavior remains unclear. In this study, we analyze the response relationship between the pore pressure field and the seepage field under transient seepage conditions. We established a numerical simulation model of multi-cluster fracture propagation in horizontal wells considering seepage forces based on the discrete element particle flow method. Using this model, we examined the mechanisms by which seepage forces affect the dynamic evolution of the induced stress field and fracture propagation behavior under various combinations of fracturing fluid viscosity, injection rate, in-situ stress, and cluster spacing. Numerical simulation results indicate that the infiltration of fracturing fluid into rock pores and the resulting seepage forces significantly alter the propagation patterns of inter-cluster fractures and the distribution of the induced stress field. Under the influence of seepage forces, hydraulic fractures suppressed by stress shadows are redirected and captured by adjacent fractures. Selecting appropriate fracturing fluid viscosity and injection rate can effectively utilize seepage forces to mitigate the inhibitory effects of the high compressive stress zones within stress shadows on intermediate fracture propagation, thereby increasing the likelihood of inter-fracture communication and the formation of a complex fracture network. This study not only underscores the importance of considering seepage forces in the design of multi-stage fracturing treatments but also provides critical theoretical insights for optimizing fracturing operation parameters.