Resolved CFD-DEM simulation of proppant aggregating and bridging mechanisms in a narrowing fracture

In this work, we establish a resolved coupling model that integrates computational fluid dynamics and discrete element method (i.e., resolved CFD-DEM) to numerically reproduce the proppant bridging phenomenon reported in previous experiments and further reveal the underlying mechanisms leading to proppant bridging. Out study reveals that the CFD-DEM model with the consideration of an appropriate cohesion energy density parameter (e.g., 5 × 104 N/m2 in our models) can reasonably well capture the micro-scale dynamic features of proppant aggregating and bridging occurring at the fracture tip. Moreover, our simulations indicate that the critical ratio of the fracture width to the mean particle diameter leading to proppant bridging is approximately 1.9, which agrees well with experimental results. In a closed boundary fracture model considering fluid leak-off, proppant size significantly influences aggregating locations: smaller proppants are trapped close to the fracture tip, while larger proppants are aggregated at locations close to the fracture inlet.