Effect of fracture roughness on transport of suspended particles in fracture during drilling

Abstract

Fractures with different roughness are important permeable channels in oil and gas reservoirs. However, the drilling fluid is prone to leakage through fractures, resulting in formation damage. Study on the migration behavior of suspended particles with drilling fluid loss is the basis for finding the damage mechanism of solid invasion and drilling fluid loss control measures. From a comprehensive review of the previous studies, the transport behavior of suspended particles considering particle-fluid-fracture interaction hasn't been fully understood and quantified. In this study, we examined flow behavior of the particle-fluid mixture by the unresolved CFD-DEM approach. The effects of particle concentration, particle size, fracture width, drilling fluid loss rate, drilling fluid viscosity and cohesive force on particle transport in different rough fractures were studied. The research suggests that: (1) Increase of particle concentration will not only result in significant increase in fluid-particle velocity, but will also increase the wall mechanical retardation. (2) Particle aggregation near the fracture walls is more serious than in the fracture center. The shape of the agglomeration particle clusters is mainly elongated, with the long axis direction consistent with the flow direction. (3) Rough fracture walls will not only lead to more energy loss due to frequent particle-particle and particle-fracture contact, but also cause more particles to migrate in the fracture center.