Plugging mechanism of preformed particle gels in fractured formation: Development of dynamic gelling model

Preformed particle gels (PPGs) have been demonstrated as effective materials for fracture plugging. However, the dynamic migration and distribution patterns of gel particles within fractures remain unclear; the relationship between gel migration and plugging effectiveness is not well-defined, and the underlying plugging mechanism is yet to be fully understood. By accounting for the interaction forces between gel particles, this study develops a dynamic gelling model for PPGs in fractured formations using a multiscale coupling approach. This model enables in-depth analysis of particle migration and plugging behavior. Simulation results indicate that the hydrogen bond force and the liquid bridge force play dominant roles in the gelling process, accounting for 46.4 % and 28.5 %, respectively. The plugging process can be divided into four stages: migration, gelling, plugging, and stabilization. The gel cluster structures evolve from disordered to ordered, from small clusters to long chains, and ultimately form stable clustered gel structures. The pressure after fracture plugging increases from 0.059 MPa to 0.222 MPa, a rise of 2.76 times, confirming the effectiveness of fracture plugging. Within the plugged zone, a relatively small number of strong force chains support the majority of the external load on the particle system, determining the structural strength. Meanwhile, uniformly distributed weak force chains interact with the strong force chains, playing a critical role in maintaining shear stability. The study verifies that PPGs can rapidly form stable gel networks in fractures, significantly enhancing plugging performance. The proposed model offers valuable theoretical and technical insights for mitigating well leakage in complex formations.