Critical sand deposition velocity for gas-liquid stratified flow in horizontal pipes

Abstract

Sand is frequently produced along with production fluids from a reservoir with low formation strength. Sand deposition in pipeline causes problems such as equipment failure, pipeline erosion, excessive pressure drop, and production decline. Operating above critical sand deposition velocity, which is the velocity that keeps particles moving all the time at the pipe bottom, is the best strategy to manage sand deposition and simultaneously optimizing production flow rates. In this paper, a comprehensive study of sand flow regimes in air – PAC (Polyanionic Cellulose) water stratified flow in horizontal pipelines for various sand concentrations upto 10,000 ppm is presented. Six sand flow regimes are observed, namely, fully dispersed solid flow, dilute solids at wall, concentrated solids at wall, moving dunes, stationary dunes and stationary bed. 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 viscosity of water is increased to 5 cp by using PAC to investigate the effect of viscous sublayer. The experimental data for tested conditions show that for concentrations above 4000 ppm, stationary beds are observed at the pipe bottom, and bigger particle size has higher critical sand deposition velocities, while for concentrations less than 4000 ppm, stationary dune and stationary bed are observed, and the critical sand deposition velocity depends on which sand flow regime occurs at the pipe bottom.