Numerical Simulation of Proppant Transport in Field-Scale Fractures with the Multi-Phase Particle-In-Cell Method

Abstract

Slickwater fracturing is one of the key techniques for successful development of unconventional reservoirs. However, due to the low viscosity of slickwater, proppant-suspending capacity is very limited. Proppants settle down quickly in the fracture and form a proppant bed. The traditional continuous model for simulating proppant transport cannot capture the main physics of proppant transport in the slickwater and predict proppant placement. The models of Computational Fluid Dynamics Discrete Element Method (CFD-DEM) are computationally demanding and only can simulate proppant transport in the small-scale fractures. This study applied the Multiphase Particle-in-Cell (MP-PIC) model to simulate the proppant transport process in a field-scale fracture.

The present simulation attempts to study the effect of crucial factors (fracture height, proppant concentration, fluid viscosity, and injection rate) on proppant placement. We constructed a 180 m long vertical fracture for simulation. When we injected 40/70 mesh proppants into this field scale fracture, the case studies can be performed. Our simulation results show as follows:

• When the fracture reaches a certain height, increasing fracture height has an insignificant effect on proppant placement. Decreasing this certain height can result in longer proppant length due to a stronger wash-out effect. • The viscosity is sensitive to the proppant height. The proppant bed height will decrease significantly with a larger fluid viscosity. • The injected slurry with relatively low proppant concentration can form a longer proppant length. • Changing the injection rate without adding more proppant will not influence the final proppant distribution. • Proppants injected at different times can distribute differently with various injection rate. • The higher injection rate and proppant concentration can respectively help injected proppants reach proppant dune height and maximum fracture length faster.