CFD-DEM Simulation Analysis of the Effect of Sweep Stages on Proppant Placement within Rough Fracture

Abstract

Hydraulic fracturing is a conventional measure to enhance recovery. Proppant transportation as a critical technology of hydraulic fracturing can maintain the effect of production enhancement. A validated Computational Fluid Dynamics - Discrete Element Method (CFD-DEM) method is used in this paper to study the generation condition of blocky dune and the impact of proppant placement in rough fractures during the sweep stages. The results indicate that medium-sized aperture proppants have more possibility of generating blocky dune. These blocky dunes possess distinctive properties that can lead to complications, such as the plugging of fractures. Intriguingly, this phenomenon is unique to proppant transport within rough fractures. Contrary to initial predictions, concentration, and injection velocity exert minimal influence on the genesis of blocky dunes. Dunes formed at lower injection velocities should be subjected to water scouring at higher velocities. Additionally, a critical velocity threshold, determined by the fracture's characteristics, exists for the injection velocity during the sweep stage. If the velocity dips below this critical threshold, the sweep stages lose their effectiveness. This investigation elucidates the generative conditions of blocky dunes and their properties about rough fractures during sweep stages, offering valuable insights for the optimization of proppant placement strategies in practical engineering scenarios.