Evaluation of Pipeline Sand Sampling Practices in Petroleum Industry

Abstract

Abstract The goal of this work was to examine the effect of sand sampling location and method on the measurement of particle concentration. Sand concentration is a major factor in finding the optimal operating condition, and pipeline sampling is believed to be an accurate approach to detect and determine the particle concentration. The current work shows that to obtain a representative sand sample flowing in pipe in multiphase flow, additional parameters should also be considered when sampling such as orientation of the pipe, type of fitting, sand size, flow velocity and the flow regime in the vicinity of the sampling location. Experiments have been conducted in single-phase and multiphase flow conditions, and the effect of pipe size, particle size, sampling location and flow velocity and viscosity on the sampled concentration is studied. The liquid-sand samples are collected using sampling ports placed in the pipe wall in horizontal and vertical sections of the pipe. The particle concentration in the liquid-sand sample is compared with the flowing bulk concentration to find the best representative sampling practice. Computational Fluid Dynamics (CFD) simulations are conducted for various cases to determine the particle tracks in the pipe and obtain insight to the fluid-particle interaction. It was found that the particle concentration in the samples collected from different locations are consistent with the bulk flowing concentration for small particles sizes (25 and 75 μm), but significant deviation is observed for large particles (150 and 300 μm) especially for samples collected from the bottom of the horizontal line in multiphase flow. While sampling in the vertical section of the pipe away from the bend provided the best results for most of the cases, the sampled concentrations along the inner radius of the pipe were observed to be higher than corresponding values along the outer radius. Based on the CFD simulation results, this may be attributed to the effect of secondary vortices that develop in the bend. For liquid dominated multiphase flows, the sampled concentration was relatively uniform as particles experience significant drag in the liquid phase and become dispersed inside the pipe, but in annular flow in the vertical section, notable differences were observed between the samples collected from the inner side versus the outer side.