Proppant placement plays a crucial role in ensuring the conductivity of fractures is maintained after a hydraulic fracturing treatment. The process involves the transport of solids suspended in a liquid (usually a water-based fluid) from the wellbore through the perforations and finally into the fractures. Many studies have focused on proppant settling and transport in fractures but relatively few studies have investigated the transport of slurries through perforations into the fracture. The paper addresses the important issue of proppant transport through perforations by modelling the fundamental physics involved in the process. The objective of this paper is to evaluate the efficiency of proppant transport in a perforated horizontal well under different suspension flow conditions.

In this paper, proppant transport through a perforated horizontal casing is modelled using a combined CFD-DEM approach. The model is validated by comparing its results against published experimental data. The effectiveness of proppant transport is evaluated by the particle transport efficiency (E_i), which is defined as the mass fraction of particles transported through the perforations relative to the total mass of particles injected. The effects of changing particle size, particle density, solids volume concentration, pumping rate, fluid rheology, perforation size, and perforation orientation on E_i are investigated.

The results show that the perforation orientation has a large influence on E_i especially at low pumping rates. Under such conditions, solids concentration in the low side perforation is always larger than the injected solids concentration while solids concentration in the high side or sideways perforation is always smaller than the injected concentration. An increase in particle size, particle density, and a decrease in fluid viscosity leads to an increase in E_i for low side perforations and a decrease in E_i for high side perforations. Increase in pumping rate and fluid viscosity helps to even the proppant distribution among perforations with different orientations; the solids concentration in perforations in both scenarios, however, are smaller than the injected solids concentration regardless of perforation orientation. An increase in upstream solids concentration is found to have negative effect in E_i for perforations in all orientations. Finally, an increase in perforation size is found to increase E_i for low side and sideways perforations at low pumping rates but shows an insignificant effect on E_i for high side perforations.

The numerical model results are compared with experimental data and excellent agreement is observed.  Results from this paper enhance our understanding of proppant transport from the wellbore into fractures and provide guidelines for engineers to follow to better control proppant distribution in perforation clusters in horizontal wells.