Numerical simulation on oil-water-particle flows in complex fractures of fractured-vuggy carbonate reservoirs

The reservoir spaces of the carbonate reservoirs in the Tahe oilfield consist of fractures and vuggies. The injection of particle plugging agents to control the dominant channel of water flooding is an important measure in enhancing oil recovery. In this paper, a simplified parallel fracture is used to represent the complex fracture structure, and an oil-water-particle three-phase flows computational fluid dynamics model based on the volume of fluid-discrete element method (VOF-DEM) model is established to study the particle transport and accumulation behaviors after water flooding in the fractures. The results show that the injected particles are transported and accumulate along the water phase channel in the main fracture after water flooding but barely flow directly into the secondary fracture. The particle accumulation in the main fracture reduces the cross-section of the water phase flow channel, which leads to an increase in the pressure loss in the main fracture and the flow ability in the secondary fracture. The oil-water interface at the top of the accumulation changes during the process of particle injection, which is beneficial in enhancing oil recovery. The simulation results of different parameters show that the injection velocity, particle volume fraction, and particle diameter affect the position, length, and height of the particle accumulation in the main fracture, which exhibits an important influence on the oil-water interface in the main fracture and the flow ability in the secondary fracture.