Numerical investigation of fluid flowing through rough fractures subject to shear

Abstract

Comprehending fluid flow in rock masses is essential for modern underground engineering, including chemical energy extraction, nuclear pollutant remediation, and hydrocarbon utilization, complicated by shear-induced and surface roughness effects in fractures. This study employed numerical simulations to investigate the fluid flow behavior in fractures with different surface roughness under shear, where the shear direction is perpendicular to the flow direction. The nonlinear flow of the fluid is observed to have a strong correlation with the confining pressure (Pz), roughness (JRC), and shear displacement (u). The generation of eddy currents is frequently linked to the presence of flow channel intricacies and the velocity of flow at a microscopic scale. The Forchheimer equation could describe the process of nonlinear phenomena accentuation very well. The fracture under Pz caused a reduction in hydraulic transmissivity (T) due to compression. Furthermore, the T changes dramatically as the shear process progresses. Based on the analysis of the Forchheimer coefficient (β) and critical Reynolds number (Rec) parameters used to determine the response of nonlinear flow, it appears that an increase in Pz facilitates the transition of the fluid into a nonlinear flow state. Conversely, shearing has the opposite effect and reduces the tendency toward nonlinear flow.