Experimental Study of Proppant Bridging in a Model of a Hydraulic Fracture

In this article, we investigate formation of the local clogging (bridging) of proppant in a channel with gradually narrowing walls. The experimental facility allows us to simulate the process of the proppant transport in a hydraulic fracture by reproduction of the characteristic channel width, velocity of slurry, rheology of fracturing fluids, and typical concentrations of proppant. The goal of the study is to give qualitative description of the dynamics of the congestion of the proppant up to the complete blockage of the flow. In contrast to common practice of imposing bridging criteria by postulating certain threshold value of the width to proppant size ratio, we demonstrate that the bridging process involves several stages: clogging of two to three particles, growth of stable "islands," connection of the islands by arches, and, finally, the total sandout of the cell by the bridged proppant. The observations of the paper gives better understanding of the bridging process giving the directions for more precise numerical simulations.