Research on the Migration and Placement Laws of Proppants in Fractures and Key Influencing Factors during...

The supercritical CO₂ (Sc-CO₂) fracturing technology has attracted extensive attention in the field application, especially reservoir stimulation for unconventional oil and gas reservoirs due to its low reservoir damage rate and unique physical property advantages. Our article uses the computational fluid dynamics and discrete element method (CFD-DEM) numerical simulation method to establish a Y-shaped main-branch fracture model that reflects the actual oilfield conditions, and analyzing the influence of injection temperature, the angle of the main and branch fractures, proppant particle size, and the fracturing fluid flowback process on parameters such as the proppant morphology is carried out. The results show that ① During the injection stage, Sc-CO₂ has a weaker sand-carrying performance due to its low viscosity, and it is more likely to accumulate in the near-well section of the wide main fracture to form a high sand bank. ② Fractures with a small included angle (e.g., 30°) are conducive to the inflow of proppants into the branch fractures but are more prone to reverse scouring during the flowback stage, with the sand production rate reaching up to 34.15%. ③ During the flowback stage, the smaller the proppant particle size, the lower the critical flowback velocity. For example, when the proppant particle size is 0.05 mm, a flowback fluid velocity exceeding 0.15 m/s will trigger a large-scale backflow of proppant. Our article can provide an important theoretical basis for the optimization of Sc-CO₂ fracturing.