Study on the Overflow Pattern of Irregular Particles in Microcracks

The present study aims to address the challenge of effective proppant entry in microfractures (seam width of 50~200 μm) following the fracturing of shale gas reservoirs. To this end, a systematic exploration of the mechanism by which irregular particle shapes influence the overflow pattern of microfractures is conducted through CFD-DEM coupled numerical simulation and experimental validation. The study's foundation is rooted in the empirical scanned particle morphology, leading to the establishment of a geometric model encompassing a trapezoidal micro-seam composite structure. The model is further populated by four distinct particle populations, each exhibiting varying degrees of sphericity ranging from 0.57 to 1.0. The simulation process is meticulously conducted under specific conditions, namely a seam width of 0.1 mm and a sand ratio of 10%, while employing a unified particle size parameter of equivalent volume equivalent diameter. The simulation results demonstrate that particle shape exerts a substantial influence on overflow capacity, and the critical overflow size ratio (particle volume equivalent diameter/seam width) exhibits a non-linear relationship of increasing and decreasing with the increase of sphericity, reaching a peak at 0.74 sphericity (the most difficult to clog), while the shape effect of particles with high sphericity (>0.80) is weakened. The results provide a theoretical basis for the optimisation of proppant shape and precise selection of particle size in shale gas reservoir fracturing. Furthermore, the microfracture support efficiency can be significantly improved by selecting optimal particles, which is an important guiding value for the improvement of fracturing effect and extraction efficiency.