Proppant Transport in Rough Fractures of Unconventional Reservoir– A Case Study from China

Abstract A generative method for fractures with rough surfaces was established based on fractal interpolation theory, encompassing interactions among particles, particle-wall, and particle-fluid. Consequently, a coupled computational fluid dynamics (CFD) and discrete element method (DEM) model was developed to simulate the two-phase flow of proppant and fracturing fluid within these fractures. Validated by experimental data, the model effectively matches the transport and accumulation processes of the proppant in rough fractures. Comparative numerical simulations across various scenarios revealed that, when compared to smooth planar fractures, the transport and deposition of proppants in rough fractures are significantly affected by the wall roughness. The greater the surface roughness, the faster the proppant particles settle near the fracture inlet and the shorter their horizontal transport distance, resulting in a tendency to accumulate near the fracture entry and rapidly form sand plugs within the crack. The roughness of fracture walls can control the fluid’s flow path to some extent, altering how the proppant fills the fractures. On one hand, the elevated roughness lifts the trajectory of proppant movement, causing more proppant to exit the fracture and thereby reducing coverage; on the other hand, the fracturing fluid is more likely to redirect its flow near the contact points of the rough surface protrusions, potentially expanding the coverage area of the proppant.