Investigating Flow Regimes in High Temperature High Pressure HPHT Gas Subsea Tieback

Abstract

Abstract Flow assurance is of significance importance in the oil and gas industry as the produced fluids are typically multiphase in nature. Multiphase flow is the flow of two or more phase in a conduit. The density and viscosity difference of the phases results in the phase separation and difference in pipe wall shear stresses for each phase. The most characteristic feature of multiphase flow is the flow regime (or flow pattern); which is the variation in the physical distribution of phase in the flow conduit. This work seeks to provide a better understanding of flow regimes in a long-distance high pressure and high temperature (HPHT) gas subsea tiebacks with a view to help predict and mitigate potential flow assurance issues. Computational fluid dynamics (CFD) using volume of fluid (VOF) model was used to identify flow regimes, analyse pressure drop and temperature for various gas to liquid concentrations and varying initial gas velocity for horizontal and vertical pipe. The results show elongated bubble, stratified smooth, stratified wavy, slug and dispersed bubble annular flow regimes for horizontal pipe, and elongated bubble, churn, slug and dispersed bubble annular flow regimes for vertical pipe. The ability to predict the expected flow regimes for a subsea tieback will enable the use of appropriate mitigation technique for potential flow assurance issues.