Composite temporary plugging mechanism in horizontal well perforations

In multi-stage fracturing of horizontal wells, fracture-opening temporary plugging is crucial in ensuring the uniform propagation of hydraulic fractures. Large-displacement, high-intensity sanding fracturing often causes severe perforation erosion, which in turn affects the performance of plugging. A composite temporary plugging method that combines ball-sealers and temporary plugging agents (TPAs) is commonly used to enhance the plugging efficiency. However, due to the size disparity between them, conventional numerical simulation methods face challenges in modeling such cross-scale particle systems. To address this issue, a hybrid computational fluid dynamics-discrete element method model was developed using the fictitious domain method and statistical kernel functions. This model was employed to study the formation and evolution of composite temporary plugging at perforations under varying conditions. The results indicate that intense axial acceleration in the upstream inhibits particle bridging, whereas reduced velocity and vortex formation downstream create favorable conditions for plug formation. During the plugging process, a perforation plugging forms only when the concentration of TPAs exceeds a critical threshold. This threshold decreases with increasing particle diameter, but larger particles at lower concentrations tend to form less dense plugs. Notably, due to flow asymmetry, particle accumulation and bridging occur more readily downstream of the perforation. Two characteristic bridging modes were identified: single-particle bridging, which occurs when the particle diameter is too large to pass through the gap between the perforation and the ball-sealer; and multi-particle bridging, driven by the accumulation of smaller particles at higher concentrations in low-velocity regions.