Study of Proppant Erosion in Multistage Hydraulic Fracturing Using Computational Fluid Dynamics Modeling

摘要

Multistage hydraulic fracturing is widely applied for developing unconventional reservoirs with low permeability. The plug-and-perf method is the most commonly used staging method especially for horizontal wells. Fracturing fluids are usually pumped from the surface to create fractures after perforation clusters are established for each stage; next, proppants are placed into the fractures to keep them open. Field and experimental work have shown that proppant transport in multistage plug-and-perf completions can cause severe erosion on perforations. However, modeling proppant erosion process is still an intricate task that proves to be challenging within the industry due to complexity of the problem. In this work, proppant erosion is investigated by using computational fluid dynamics (CFD) modeling. The effects of sand particle diameter, proppant loading, fracturing fluids viscosity, slurry injection rates, and the pipe angle are analyzed to determine the rate of erosion within the perforations. Several erosion models are used and the simulation results are compared. The numerical simulation results produced by using the proposed CFD model indicate that proppant can increase the diameter of the perforation. The unevenness of diameter increasing would further compromise the fracturing design because of one cluster accepting more fluid than its counterparts and affecting the distribution of the proppants in the cluster. The flow lines and couplings also show significant wear due to proppant erosion. The simulation results using the Oak erosion model are found to agree with the findings in the inside-casing experimental test. The results of this study indicate that proppant erosion in multistage hydraulic fracturing can be accurately modelled when proppant properties, fracture geometry, and slurry rheology are all considered in the CFD simulation model. The simulation methodology proposed and discussed in this paper provides a better understanding of fluid and proppant behavior and proves that CFD is an effective tool for reducing the wear of perforations and pipes caused by proppant erosion and hence, optimizing hydraulic fracturing design.