The work aims to improve understanding of proppant transport and evaluate foam effectiveness for hydraulic fracturing in the oil and gas industry. In recent years, hydraulic fracturing has been of particular importance for unconventional oil and gas production. For this process, the reservoir rock is fractured under high hydraulic pressure in the well to maximize well-reservoir contact and create channels for reservoir fluid flow to the wellbore. As the essential step of the fracturing operation, proppant is pumped through the wellbore into the reservoir to support the created fracture path and avoid the fracture closure. The fracturing fluid, such as foam and gel, exhibits complex rheology. Many studies have been done on foam rheology. However, it is particularly challenging to predict the proppant tranpsort due to the complex physics involved, including fluid dynamics, fluid rheology, multiphase flow, solid size and shape, etc. Hence there are limited modeling studies on the capacity of these fluids in transporting proppant in the fracture.
In this paper, we used computational fluid dynamics (CFD) to simulate proppant transport in fractures and gain insight into the complexity of slurry flow. The numerical model couples the complex non-Newtonian fluid rheology of foam as fracturing fluid with the solid-solid and solid-fluid interactions using Euler-Euler method, assuming uniform spherical sand. The model captures the sand particle gravitational settling and sand bed propagation in fractures. The solid proppant and flow simulation model was validated by empirical correlation for single particle settling. Simulation results in 2D and 3D fracture models are compared with published experiments, and 3D simulations show a good match to experiment. The effectiveness of foam fracturing fluid on sand transport is demonstrated by comparing it to water fracturing fluid. The simulation model also reveals the significant impact of dimensionless convection number and fracture width on sand transport in the fracture. Results in this work demonstrated the impact of fluid rheology and enhanced the understanding of the flow of proppant and fracturing fluid within a fracture, which can be used to help lab experiment and fracturing process design.