Experiments of Sand Distribution among Perforation Clusters in a Horizontal Pipe

ABSTRACT Multistage horizontal fracturing is the key technique in developing shale gas reservoirs. Although the parameters of perforation clusters are almost the same in each stage, production from each perforation cluster is vastly different. One of the factors that influences gas production between perforation clusters is the uneven proppant distribution among perforation clusters. In order to investigate proppant distribution among perforation clusters, the theory on proppant settling along horizontal lateral is presented to calculate the minimal critical velocity. Meanwhile, experiments on 20/40 and 40/70 mesh sand distribution with different concentrations were conducted at different pumping rates utilizing slick water fluids. The experimental parameters of perforation cluster, such as perforation density, length, and distance between clusters are scaled to simulate the actual treatment in shale gas fracturing. Therefore, the experimental results in this study can represent the actual distribution of proppants among perforation clusters. The results are analyzed, and some conclusions are presented. Pumping rate and viscosity are the two important factors that can have a big impact on the sand distribution. At a lower pumping rate, more sand was deposited at the first perforation cluster, whereas at a high pumping rate, more sand was deposited at the third cluster. The viscosity of slick water will also affect sand distribution largely. At a low fluid viscosity, sand distribution was varied much among clusters at the same pumping rate, and sand tended to distribute evenly when the fluid viscosity is increased. Therefore, in order to distribute proppants evenly among perforation clusters, the treatment parameters such as the pumping rate or the viscosity of slick water fluid can be adjusted accordingly.