Simulation of proppant transport in complex fracture networks based on the multiphase particle-in-cell method

A three-dimensional multiphase particle-in-cell (MP-PIC) method was adopted to establish a liquid-solid two-phase flow model accounting for complex fracture networks. The model was validated using physical experimental data. On this basis, the main factors influencing proppant transport in fracture network were analyzed. The study shows that proppant transport in fracture network can be divided into three stages: initial filling, dominant channel formation and fracture network extension. These correspond to three transport patterns: patch-like accumulation near the wellbore, preferential placement along main fractures, and improved planar placement as fluid flows into branch fractures. Higher proppant density, lower fracturing fluid viscosity, lower injection rate, and larger proppant grain size result in shorter proppant transport distance and smaller planar placement coefficient. The use of low-density, small-diameter proppant combined with high-viscosity fracturing fluid and appropriately increased injection rate can effectively enlarge the stimulated volume. A smaller angle between the main fracture and branch fractures leads to longer proppant banks, broader coverage, more uniform distribution, and better stimulation performance in branch fractures. In contrast, a larger angle increases the likelihood of proppant accumulation near the branch fracture entrance and reduces the planar placement coefficient.