Sand Transport in Stratified Flow in a Horizontal Pipeline

Abstract

Abstract The entrainment of sand in crude oil occurs during production from reservoirs with low formation strength. The stationary sand bed at the pipe bottom can cause operational problems such as production decline, excessive pressure loss, equipment failure, erosion and corrosion. Sand deposition can be managed by operating above critical sand deposition velocity, which is the velocity that keeps particles moving all the time at the pipe bottom. A comprehensive analysis of sand flow regimes in stratified flow in horizontal pipeline is presented here, which is a novel contribution in this paper. Also, the effect of concentration on the sand flow regimes and identification of critical sand deposition velocities for various concentrations are investigated in this paper. The understanding of sand flow regimes in pipelines for any given set of operational conditions is important to identify the nature of particle interaction and movement. Experimental studies have been conducted at stratified flow regime with air-water-glass bead at relatively low sand concentrations (<10,000 ppm). The effects of different experimental conditions such as gas velocity, sand concentration, and particle size have been investigated in this study. Six main sand flow regimes in horizontal air-water flow are identified, which can be distinguished visually: fully dispersed solid flow, dilute solids at wall, concentrated solids at wall, moving dunes, stationary dunes and stationary bed. Therefore, the critical sand deposition velocities are determined based on the transition between moving (concentrated solids at wall/ moving dunes, as appropriate) and stationary (stationary dunes/bed, as appropriate) sand particles. The experimental data shows that with small particle size, the critical sand deposition velocity is almost independent of concentration, while with bigger particle sizes, the critical velocity increases with the concentration.