Achieving Uniform Proppant Distribution in Horizontal Wellbore Clusters Using CFD Modeling

Slickwater multi-stage hydraulic fracturing is one of the most effective technologies for stimulating unconventional reservoirs. However, achieving uniform proppant distribution between perforation clusters in slickwater fluids remains a significant challenge due to the low viscosities. Several studies have focused on proppant placement in the wellbore, but relatively few have focused on the variations in proppant distribution between sealed and leaking plugs. In this study, a computational fluid dynamic (CFD) model was developed to investigate uniform proppant distribution between the perforation clusters without fluid leakage from the plug. The CFD model was initially developed using a laboratory-scale geometry and validated against experimental data of the proppant distribution in a horizontal wellbore. The laboratory and base model consist of a 1.5-in diameter, 30 ft long wellbore with three perforation clusters spaced 7 ft apart. Each cluster has 4 shots per foot (SPF) perforations with a 0.25-in diameter and a 90ºphasing. A small valve was placed at the end of the wellbore section acting as a sealed plug. Subsequently, the model was scaled up to a 51 ft long wellbore with six perforation clusters of identical diameters and spacing. The initial model was used to investigate the effects of various injection parameters on proppant distribution, whereas this scaled-up model was used to evaluate the effect of perforation orientation and configuration on the proppant distribution. Both lab and CFD model results show that closing the back valve without leakage affects the amount of the proppant placement in the last two toe clusters compared to those with leakage. This leads to less proppant settling in the toe cluster and more proppant settling in the preceding cluster. The leaking plug model showed all bottom perforations receive significantly more proppant, while the sealed plug model showed the last cluster's bottom perforation receives less proppant due to a plugging effect. The model results show that higher proppant density and larger particle sizes result in non-uniform proppant distribution with less proppant settling in the toe cluster. Higher proppant concentrations resulted in non-uniform proppant distribution, with more proppants being transported towards the toe clusters. The scaled-up model results show that the perforation orientation significantly impacts proppant distribution. Changing the perforation phasing from 90ºto 70ºresults in a uniform proppant distribution in a 2 SPF case. Additionally, a 4 SPF top perforation configuration with a 0° phasing displayed different proppant transport and distribution phenomena compared to a 90ºphasing.