Achieving Uniform Proppant Distribution in Horizontal Wellbore Clusters Using Computational Fluid Dynamics Modeling

Slickwater multistage 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. While some studies have explored the impacts of leakage past bridge plugs in plug-and-perf systems, the effect of high-integrity sealed plugs on proppant distribution inside fracturing stages remains unexplored. For this study, we developed a computational fluid dynamics (CFD) model to investigate the proppant distribution between the perforation clusters with a fully sealed 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 consisted of a 1.5-in.-diameter, 30-ft-long wellbore with three perforation clusters spaced 7 ft apart. Each cluster had 4 shots per foot (SPF) perforations, with a 0.25-in. diameter and a 90° phasing. A small valve was placed at the end of the wellbore section, acting as a sealed plug by completely preventing fluid from moving past. 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 the scaled-up model was used to evaluate the effect of perforation orientation and configuration on the proppant distribution. Both laboratory and CFD model results showed that placing a fully sealed plug affected the amount of proppant placed in the last two toe clusters, which contradicts the results of those with a leaking plug. This led to less proppant settling in the toe cluster and more proppant settling in the preceding cluster. The leaking plug model showed that all bottom perforations received significantly more proppant, while the sealed plug model showed the last cluster’s bottom perforation received less proppant due to a plugging effect. The model results showed that higher proppant density and larger particle sizes resulted in nonuniform proppant distribution with less proppant settling in the toe cluster. Higher proppant concentrations resulted in nonuniform proppant distribution, with more proppants being transported toward the toe clusters. The scaled-up model results showed that the perforation orientation significantly impacted proppant distribution. Changing the side perforation phasing from 90°/270° to 110°/250° resulted in a uniform proppant distribution in a 2-SPF case. Additionally, a 4-SPF top perforation configuration with a 0^o phasing displayed different proppant transport and distribution phenomena compared with a 90° phasing.