One of the most significant components of hydraulic fracturing modeling is the prediction of proppant transport in both the wellbore and fractures, as the resulting conductivity has a great impact on post treatment production. In multistage horizontal well treatments, the distribution of proppant between multiple perforation clusters has a substantial impact on treatment behaviors and results. If the proppant is not evenly distributed between the perforation clusters, the perforated intervals will not be equally stimulated. Only a few studies evaluating proppant transport in horizontal wellbores are found in the literature. This paper aims to investigate the parameters that have a large influence on the proppant settling in the wellbore and distribution of the proppants between perforation clusters, as well as providing insight into post-treatment flowback behaviors.
The approach to this work uses a model of a horizontal wellbore with three perforation clusters at shot densities of 4 SPF with 90-degree phasing. Fresh water was used as a carrier fluid to transport the proppant in the horizontal pipe. Two different types of proppants, sand and ultra-light-weight ceramic, of varying mesh sizes were used. Two design parameters, injection rate and proppant concentration, have been varied throughout the experimental tests.
The results from this work demonstrate that proppant settling velocity in the wellbore is different for each type of proppant. These differences are mainly due to the changes in the proppant concentration as well as the changes in the size and shape of proppant particles. The uneven proppant distribution between perforation clusters was mostly observed in cases where the density of proppnat was relatively high and at low flow rates. However, at high flow rates, the toe cluster received the largest amount of proppant. This occurs because the high flow rates near the first and second clusters prevent the proppant particles from turning into the perforation tunnels. The ultra-light weight ceramic shows the most even distribution between the perforation clusters since the density difference between the carrier fluid and the proppant particle is relatively low. The most significant finding is that the low viscosity fluid (fresh water) is not an effective transport system for larger particles with relatively high densities.
The results obtained from this study can be used to improve the understanding of good practices of fracture stimulation flushing, as well as proppant distribution/deposition throughout the horizontal pipe during the fracture stimulation treatment and during flowback processes.