The multiphase separators are generally the first and largest process equipment in an oil production platform, furthermore this primary separation step is a key element in the oil and gas production facilities in that downstream equipment, such as compressors, are completely dependent on the efficient performance of these multiphase separators. This research project applied Computational Fluid Dynamics (CFD) based simulation to model multiphase separators. In order to capture both macroscopic and microscopic aspects of multiphase separation phenomenon, an efficient combination of two multiphase models of the established commercial CFD package, Fluent 6.3.26, was used. The Volume of Fluid (VOF) model was used to simulate the phase behavior and fluid flow patterns, and the Discrete Phase Model (DPM) was used to model the movement of fluid droplets injected at the separator inlet. The "particle tracking" based simulation of the multiphase separation process was the key aspect of this research project, and the developed model did provide high-quality visualization of multiphase separation process. The research project involved the CFD simulation of four pilot-plant-scale two-phase separators and one industrial scale three-phase separator, including all the installed internals. There was excellent agreement between simulated phase separation behavior and the empirical observations and data gleaned from the pilot plant. The research project also evaluated the classic separator design methodologies usmg detailed CFD based simulations, and proposed improved design criteria. In order to specify an effective optimum separator, a useful method was developed for estimation of the droplet sizes used to calculate realistic separation velocities for various oilfield conditions. The most important parameters affecting these efficient droplet sizes were the vapor density and the oil viscosity. In contrast with classic design strategies, the CFD simulation results showed that additional residence times are required for droplets to penetrate through the interfaces. Moreover, the Abraham equation should be used instead of Stokes' law in the liquid-liquid separation calculations. The velocity constraints caused by re-entrainment in horizontal separators were also studied via comprehensive CFD simulations, and led to novel correlations for the re-entrainment phenomenon. Hence, this research project does show the benefits that CFD analyses can provide in optimizing the design of new separators and solving problems with existing designs.

Includes a supplementary CD-Rom.

Some pages are in colour.

Bibliography: p. 191-196