Optimization of plugging particles for dynamic fracture apertures: a coupled numerical study

Fracture aperture changes caused by downhole pressure fluctuations can alter the stress state of a plugging zone and reduce the reliability of conventional lost circulation control designs. This study establishes optimization criteria for plugging particles under dynamic fracture aperture conditions. A coupled discrete-continuum numerical model was developed to simulate particle migration, bridging, filling, and plugging-zone failure in a wedge-shaped fracture subjected to stepwise pressure loading. The model was validated using published dynamic fracture-plugging experiments, with a 1.6% difference between the simulated and experimental dynamic adaptability coefficients. The effects of particle density, particle Young’s modulus, friction coefficient, and particle size distribution on plugging-zone stability were then analyzed. The recommended particle size ratio is 65:30:5% for bridging, filling, and sealing particles, respectively, satisfying W ≥ D95 ≥ 2/3W and D30 ≥ 1/3W. Particles with higher density, higher modulus, and a larger friction coefficient are preferred within the investigated ranges. The proposed criteria account for fracture aperture variation and provide a basis for designing plugging particles in fractured formations subjected to pressure fluctuations.