Mechanistic Prediction of Oil-Water, Two-Phase Flow in Horizontal or Near-Horizontal Pipes for a Wide Range of Oil Viscosities

Abstract

AbstractThe prediction of flow patterns transition is performed for oil-water, two-phase flows over a wide range of oil viscosities. Theoretical models of oil-water systems are studied in horizontal and near-horizontal pipe flows. The equilibrium flow pattern is dependent on the oil and water properties, pipe parameters, and flow rates. Four flow patterns are considered in the mechanistic model, including stratified (ST), core-annular (CA), oil-in-water (O/W), and water-in-oil dispersions (W/O). A mechanistic criterion, proposed by Zhang and Sarica (2006) for the same purpose, is used to identify stratified flow. The Brinkman (1952) model is used to distinguish the phase inversion of oil-in-water from water-in-oil emulsions. Boundaries of core-annular flow are based on the critical core diameter given by Brauner (2003). Comparisons between the mechanistic model predictions and published experimental measurements show good agreement in regime identification.The importance of regime identification for correct pressure drop predictions is demonstrated by comparing the mechanistic model with a simple mixture model. The values of pressure drop predicted by both models are calculated and compared to existing experimental data. The mechanistic model shows significant improvement in pressure drop predictions.Dimensionless groups from Buckingham Pi theory are used to investigate the sensitivity to the input parameters. The use of dimensionless groups reduces the number of dependencies from nine input parameters to six dimensionless groups. This reduces the complexity in the optimum design of pipeline systems. From most to least sensitive, for ranges typical of pipeline flow and fluids, the pressure drop prediction depends on the superficial Reynolds number of oil, Eotvos number, pipe inclination angle, superficial velocity ratio, density ratio, and viscosity ratio.