Study on the Influence Mechanism of Fiber Properties on the Strength of Fiber-Particle Composite Temporary Plugging Layer

Temporary plugging and diversion fracturing technology is an effective method for developing shale oil and gas reservoirs. However, temporary plugging often fails due to insufficient shear strength of the temporary plugging layer. It has been proven that mixing fibers and particles to form the temporary plugging layer can effectively improve its mechanical strength, but current research results are mostly qualitative analyses. In this paper, we present a DEM-based model to predict the shear strength of a particle-fiber mixture temporary plugging layer. The rolling resistance model simulates interactions among particles and between particles and fibers. Fibers consist of bonded particles with a uniform diameter of 0.5 mm. The influence of fiber addition on the mechanical strength is analyzed from a mesoscopic perspective through force chains, and the effects of fiber concentration (0.1%-10%), length (3 mm-25 mm), and friction coefficient (0.2-1.6) are quantitatively studied. Adding fiber improves the mechanical strength of the temporary plugging layer. For example, with 1% fiber concentration, strength increases by 35.8% compared to pure particles. While fiber addition reduces force chain strength from 820 N (no fibers) to 630 N (1% fibers), the number of force chains increases significantly from 170 to 570, compensating for the strength loss. Strength initially increases and then decreases with higher fiber length and concentration. Maximum shear strength occurs at 0.7% fiber concentration and 20 mm length. Higher fiber concentrations and lengths reduce shear strength due to decreased particle-to-particle contact. The fiber friction coefficient increases strength initially and stabilizes at 1, having the greatest impact on mechanical strength, followed by fiber concentration, while fiber length has the least effect. This work constructs a quantitative correlation between fiber characteristics and the shear strength of composite temporary plugging layers, offering technical guidance for optimal fiber material selection and the innovation of plugging agents used in diversion fracturing processes.