Effect of Surface Tortuosity on Particle Dynamics in Rock Fractures

The transport behavior of particles in tortuous fractures is prevalent in the oil and gas extraction process and has a profound impact on engineering. However, due to a variety of factors, drilling fluid leakage is prone to occur during drilling and completion, and an evaluation system for the influence of meander characteristics on the kinetic properties of particles has not yet been established. To this end, this paper constructs a numerical model based on CFD-DEM numerical simulation to simulate the particle–fluid two-phase flow in the meandering fracture, investigates the mechanism of surface meandering on particle force, particle transport velocity, and particle residence time, and proposes a mathematical method based on meandering for predicting particle transport velocity and particle residence time in the stable transport phase. The results show that the increase in tortuosity makes the force state of particles in the fracture show significant instability and intensifies the interaction between fluid and particles in the fracture; the effect of the tortuous wall intensifies the inhomogeneity of transport velocity, and the perturbation effect of the complex path structure on the x-direction velocity of particles is stronger; and the increase in tortuosity is not conducive to particle retention in the fracture. The results of the study can provide theoretical guidance for reducing the risk of drilling fluid leakage during drilling and completion.