Study of proppant plugging in narrow rough fracture based on CFD–DEM method

Abstract

In unconventional reservoirs, hydraulic fracturing often results in narrow and rough fractures. Nevertheless, the placement in narrow rough fractures is different from conventional fractures. This study utilizes the spectral synthesis method to model these fractures, employing a validated CFD-DEM method to investigate proppant transport within them. The research identifies blocky dunes in narrow rough fractures which are different from the continuous dunes. Furthermore, the study observes additional phenomena including local generations of plugs and automatic collapses of plugs. Changing proppant density leads to the formation of complete plugs. Additional CFD-DEM simulations involve that injecting high-velocity pure fluid can unblock the plugs. Finally, the study explores the effect of fluid viscosity on unblocking and establishes a new phase diagram to guide how to unblock the plugs on-site. This work enhances our understanding of how sand-plugging happens in rough narrow fractures and helps propose effective measures for mitigating sand-plugging issues.