Numerical Simulation of Proppant Transport in Major and Branching Fractures Based on CFD-DEM.

This research investigated the effect of branching fracture, proppant, and fracturing fluid on proppant transport based on the CFD-DEM coupling model. The obtained results show that the balance height of embankment in the major fracture decreases gradually with increasing angle between major and branching fractures, while it increases gradually in the branching fracture. This is because the additional resistance of fracturing fluid flow at the joint increases with increasing angle, leading to the decrease of the fracturing fluid velocity. The proppant is prone to settling in branching fractures, resulting in the increase of embankment height in the branching fracture. At angles of 45, 60, and 90°, as the diameter of the proppant increases from 0.8 to 1.1 mm, the balance height of embankment increases slightly in the major fracture, while it decreases in the branching fracture. The frictional resistance of the fracture wall enhances the difficulty of large proppant entering the branching fracture, resulting in a decrease in the amount of proppant entering the branching fracture and a decrease of the balance height of embankment in the branching fracture. In the low-viscosity fracturing fluid, the proppant quickly deposits at the bottom of the fracture as it enters the fracture. Improving the viscosity of the fracturing fluid can significantly enhance its ability to transport the proppant. The proppant is less likely to quickly settle in high-viscosity fracturing fluids, especially when the fracturing fluid viscosity exceeds 50 mPa·s.