Perforation Plugging with Ball Sealers in Horizontal Wells: Numerical Analysis of Plugging Mechanisms

During staged fracturing of multiple perforation clusters in horizontal wells of unconventional reservoirs, variations in fluid influx among clusters limit reservoir stimulation efficiency. Regulating the activation of perforation clusters through fracture opening temporary plugging is a key technique to achieve uniform hydraulic fracture propagation and increase the volume of reservoir effectively stimulated by fracturing. However, ball sealer migration within horizontal well sections and the factors governing it remain unclear, challenging the design of effective perforation cluster plugging strategies. This study employs a coupled CFD-DEM semi-resolved numerical model with kernel-based approximations to simulate ball sealer migration and plugging within perforated sections under varying perforation cluster flow ratios (PFRs), fracturing fluid velocities, and initial radial positions of the ball sealers. Flow field characteristics were analyzed by introducing the fluid ingestion area and local velocity gradient, revealing how different factors affect the plugging performance of ball sealers. The results show that higher PFRs of perforation clusters and closer ball sealer position to the wellbore wall facilitate more effective plugging, whereas the influence of fracturing fluid velocity is relatively limited. When the fluid influx is constant, PFR exerts a stronger control on the fluid ingestion area and local velocity gradient than the cluster location, making toe-end clusters more likely to be effectively plugged by ball sealers. Modifying the initial radial position of ball sealers through decreased fluid viscosity or enhanced particle-to-fluid density ratio can increase the likelihood of perforation cluster plugging. Elevating the fracturing fluid velocity produces only a minor influence on the fluid ingestion area and the local velocity gradient adjacent to the perforations, and due to the simultaneous enhancement of axial and circumferential drag forces, it is difficult to effectively increase the temporary plugging success rate. This study identifies the key factors affecting perforation cluster plugging and their formation conditions, offering a theoretical foundation for optimizing temporary plugging design.