An Efficient Three-Dimensional Multiphase Particle-in-Cell Model for Proppant Transport in the Field Scale

Abstract

Slickwater fracturing is one of the most dominant stimulating approaches for unconventional shale reservoirs. During the treatment, proppant transport behaviors in hydraulic fractures are of great concern for their direct impact on effective fracture geometries and ultimately well performance. Many existing models used to interpret proppant transport distribution in fractures are either oversimplified or computationally unaffordable (Only performed in small to middle lab scales). In this study, a three-dimensional multiphase particle-in-cell (MP-PIC) method, following Eulerian-Lagrangian framework, was presented to investigate proppant placement and dunes formation in complex hydraulic fractures in real field scale for field scale injection time. We have established a computational configuration, which can handle both symmetrical and asymmetrical fracture geometries. By injecting slurry in the direction perpendicular to fracture plane, the fluid can distribute into two fracture wings according to fracture geometries of two sides. By use of this configuration, we have performed parametric studies of proppant size in both symmetrical and asymmetrical fracture geometries. Our results show that proppant transport behaviors are exactly the same in two fracture wings in symmetrical cases. For asymmetrical fracture geometries, there is an uneven distribution of slurry into two wings of fracturs. The fracture wing with a larger width receives majority of slurry and proppants during the whole injection process. Therefore, proppants transport faster in the fracture wing with a larger fracture width. For the effect of proppant size, symmetrical and asymmetrical fracture geometries show similar results. When proppant size is smaller than 100 mesh, proppant size does not have a strong effect on proppant transport distance both laterally and vertically, but smaller proppants tend to have a more uniform distribution in fractures. When proppants are larger than 100 mesh, proppants can have a very severe settling phenomenon, with both vertical and lateral transport distance decreasing significantly. MP-PIC method can be used to efficiently simulate proppant transport behaviors in the field scale. The simulation of proppant transport behaviors in both symmetrical and asymmetrical fracture geometries with different proppant sizes can promote our understanding of proppant transport behaviors and help us to improve fracturing design.