Oil-Phase Redistribution of Power-Law Fluids in a Guided-Vane Swirl Separator Under High-Temperature and High-Pressure Conditions

With offshore oil and gas exploration advancing into ultra-deep waters, subsea reservoirs face extreme high-temperature and high-pressure (HTHP) conditions, leading to significant alterations in crude oil properties. These changes destabilize oil–water phase distribution and impair separation efficiency in swirl separators. Non-Newtonian fluid behavior under HTHP conditions, characterized by temperature-sensitive viscosity and shear-thinning effects, further modifies the rheological response and internal swirling-flow characteristics. This study establishes a computational fluid dynamics (CFD) framework integrating Eulerian–Eulerian multiphase modeling with power-law rheology. Simulations analyzed power-law fluid behavior across a temperature range of 30–210 °C, focusing on shear-thinning effects and phase distribution. The results show that the oil-core transport fraction increased from 0.162 at 30 °C to 0.194 at 150 °C and then decreased to 0.141 at 210 °C. Although the peak tangential velocity continued to increase with temperature, the strongest central oil-phase enrichment occurred at 150 °C, indicating that stronger swirl does not necessarily correspond to stronger phase segregation. These results provide mechanistic insight and a numerical basis for subsequent scale-up studies of HTHP guided-vane swirl separators.