Numerical Investigation of Proppant Transport in Complex Fracture Geometries for Unconventional Reservoir Development

Abstract

Slickwater fracturing has become one of the most leveraged completion technologies in unlocking hydrocarbon in unconventional reservoirs. In slickwater treatments, proppant transport becomes a big concern because of the inefficiency of low-viscosity fluids to suspend the particles. This study mainly focuses on the field-scale numerical simulation of the proppant transport in slickwater fracturing. The current numerical methods to simulate proppant transport are within the Eulerian-Eulerian (E-E) and Eulerian-Lagrangian (E-L) frameworks. The E-E models treat both the fluid and particles as continua and are widely used in commercial software due to their computational efficiency and ease of implementation. The continuous phase assumption in E-E models is acceptable for proppant transport simulation in high-viscosity fluids. However, it is no longer valid in modeling proppant transport in slickwater fracturing due to complex particle transport mechanisms. To capture the discrete features of proppant transport, I adopt a multiphase particle-in-cell model (MP-PIC) within the E-L framework to simulate the particle movement in a Lagrangian fashion. Compared to other E-L models, such as the computational fluid dynamics– discrete element model (CFD-DEM), the MP-PIC method has much better computational efficiency and suits large-scale proppant transport simulation. In the first part of this study (chapters 2 to 4), I validated a high-fidelity three-dimensional (3D) MP-PIC model through an indoor experiment. I then applied it to simulate proppant transport in complicated engineering problems: proppant transport simulation among multi-cluster hydraulic fractures and the effect of proppant pumping schedules on well production. The numerical results can provide strategies for field fracturing designs. The second part of this work (chapters 5 to 7) mainly focuses on developing an integrated multi-physics hydraulic fracturing simulator by coupling a planar 3D fracture propagation model and an efficient pseudo-3D MP-PIC model. The integrated model can simulate the proppant transport in a complex propagating hydraulic fracture in a multilayer reservoir with varying stress conditions at the field scale.