Mechanism of Proppant Transport in Wedge-Shaped Rough Fractures during Supercritical CO2 Fracturing

Supercritical CO₂ fracturing, as a novel waterless fracturing technology, has attracted widespread attention in recent years. The fractures generated by the technology are often rougher and more geometrically complex. It is very important to study the transport mechanism of proppants in wedge-shaped rough fractures. The study develops a 3D wedge-shaped fracture model with rough walls and width narrowing based on computational fluid dynamics methods. The Euler–Euler model is used to simulate the solid–liquid two-phase flow. The numerical model is validated through physical experiments. The results show that in wedge-shaped rough fractures, proppants usually exhibit a transport pattern of “high accumulation–channel diffusion”. As the fracture shrinkage rate increases, this phenomenon becomes more frequent, and the sand bed tends to form a nonuniform distribution. Especially in the back half of fractures, the combined effect of narrow flow paths and rough fracture walls more easily leads to the formation of finger-like structures, particle suspension, and unfilled areas. Furthermore, the research systematically analyzed the effects of fracture wall parameters (roughness, shrinkage rate, propagation rate), proppant parameters (size, density, sand ratio), and fluid parameters (mass flow rate, temperature) for proppant transport. This study deepens the understanding of proppant transport mechanisms in complex fractures and offers theoretical guidance for supercritical CO₂ fracturing technology.