Transport of sand in multiphase pipelines occurs in the petroleum industry as sand is produced co-mingled with crude oil. Stationary sand beds are formed at the pipe bottom when the flow velocity is lower than the critical sand deposition velocity. These sand beds reduce reservoir production and affect the integrity of the pipe system due to pipeline plugging and erosion/corrosion produced by sand particles. Therefore, the production system must be designed to operate at a velocity high enough to enable transport of sand particles along the pipe. For that reason, it is crucial to predict the critical sand deposition velocity in order to maximize reservoir production.
Gas-liquid-sand flow hydrodynamics, which is commonly encountered in most reservoirs and also in oil and gas transportation pipelines, is more complex than liquid-sand flow, making the modeling extremely difficult. At present, gas-liquid-sand flow is still not well understood, with limited data available in the literature. In addition, the effect of sand concentration has not been thoroughly studied for two-phase flows transporting sand.
Experimental and theoretical investigations have been conducted in this study on gas-liquid-sand stratified flow in horizontal pipes at low sand concentrations. A 4-in experimental facility was designed and constructed and data were acquired utilizing air-water-glass beads flow. The data include measurements of critical sand deposition velocities, namely, the transition between moving and stationary beds. The data reveal that for a constant superficial liquid velocity, the critical mixture and liquid sand deposition velocities increase with increasing sand concentrations. Also, for a given sand concentration, the critical liquid velocity is almost the same for different superficial liquid velocities.
The sand deposition correlations of Oroskar and Turian (1980) for single-phase flow and Salama (2000) for two-phase flow are modified and extended in order to develop a new correlation. The developed correlation enables the prediction of critical sand deposition mixture velocity for horizontal stratified flow, as a function of sand concentration along with other parameters. Comparison between the predictions of the developed correlation and the experimental data reveal a very good agreement, whereby the relative errors of mixture and liquid critical sand deposition velocities are ±2.5% and < 5%, respectively.