Research on particle migration in fractures driven by gas-liquid two-phase flow during deep energy storage and extraction

Abstract

Particle-laden fluid flow in fracture encompasses various deep geo-energy projects, including but not limited to hydraulic fracturing, mud and water inrush, and sand production. The migration of particles under fluid flow seriously affects the stability of geo-energy engineering and understanding the mechanisms is of great importance. This study presents a numerical investigation of particle-laden fluid flow in rock fractures under two-phase flow. A coupled approach of resolved computational fluid dynamics (CFD) and discrete element method (DEM) is employed to capture the particle movements and variations in hydraulic properties, with the volume of fluid (VOF) method to reproduce the two-phase flow. The results indicate that the model with gas injection exhibits higher particles migration velocity compared to that without gas due to the increase in fluid velocity and fluctuation in drag force. Particles migration velocity presents an initial increase followed by a subsequent decrease as the gas fraction increases, which can be attributed to the initial rise followed by a subsequent decline in the drag force. In addition, the sensitive analysis shows that the particle migration velocity decreases with the increase of liquid viscosity and fracture roughness in the fluid, and further accelerates with the increase of particle size and hydraulic gradient. Our results have important implications for understanding the mechanisms of particle migration in rock fractures driven by the multiphase flow during deep energy storage and extraction.