Numerical simulation on particle-fluid flow in fractured formations: Evolution law of plugging layers

The bridging plugging method is an economical and practical fracture loss control technology. However, it is challenging to clarify the microscopic flow behavior and plugging process of lost circulation materials in frac -tures under formation conditions. This study uses the computational fluid dynamics-discrete element method to establish a wellbore-fracture model to study the flow behaviors of a plugging slurry in fractures. The model especially considers the interaction between the wellbore wall and the plugging slurry. The results show that the evolution process of the plugging layer can be divided into four stages based on the tracking of the information on the interaction of particles, fluid, and wall. The initial structure of the plugging layer is mainly a two-sphere bridge. The formation location and subsequent construction speed of the plugging layer depend on the particle size and concentration, respectively. The optimization of particle combination can effectively enhance the structural stress of the plugging layer. The liquid viscosity has a limited influence on the sealing, and the excessively high liquid pressure will destroy the stability of the initial bridging. Quantitative research on the evolution of the plugging layer can provide a reference for optimizing the formulation design of the plugging slurry system.