The development of extensive networks of fractures, also known as complex fracturing, is necessary for improving performance in very low-permeability, mainly stress-isotropic rocks, particularly shales reservoirs. Proppant transport and placement in these fractures are significantly impacted by the combination of naturally occurring and hydraulically induced fractures, which results in a complex fracture network.

In this study a three-dimensional hybrid CFD model combined with the kinetic theory of granular flow (KTGF) is used to investigate the effect of complex fractures in the transport and placement of proppant, the simulation was first validated with experimental data, then, the effects of size, velocity and fracturing fluid viscosity for a tortuous complex fracture is investigated.

The simulation results matched well with the experimental data. According to the parametric analysis, smaller proppant size, and high fluid viscosity help in proppant transit into the secondary fracture and generate a larger effective propped area, the increase in velocity leads to proppants to be able to enter into the secondary fracture, whereas for smaller velocity the proppants stay in the main fracture. Additionally, tortuous complex fractures geometry led to more resistance opposite to the flow direction and make more difficult the proppant transport.

This research helps to improve the hydraulic fracturing design for shale formations by extending our understanding of proppant transport in complex tortuous fracture systems using a hybrid CFD approach.

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