CFD Modeling of Subsea Gas Releases Using an Improved Bubble Drag Law

A subsea gas leakage from pipelines, risers, gas transport pipelines or blowouts from oil and gas wells forms dispersion of gas as it rises to the surface. Accidental subsea gas release scenarios of hydrocarbons pose a significant risk for the safety and integrity of offshore production or drilling units. With recent advancements in technology, the number of subsea installations and pipelines increases substantially at larger water depths. For the large depths, it is crucial to understand the quantitative impact of the gas release as the classical integral bubble plume models fail to predict gas flux and gas distribution through the ocean surface and the resulting surface flows. A quantitative multiphase computational fluid dynamics (CFD) model can be implemented to simulate large scale bubble plumes by tracking bubbles and free surface in a Eulerian-Lagrangian fashion. In this paper, the coupled discrete phase (DPM) and volume of fluid (VOF) multiphase modeling approach has been utilized for modeling subsea gas releases. This study evaluates an improved drag law for gas-liquid two phase bubbly flow based on consideration of bubble deformation. The model successfully predicts a wide range of experimental measurements at model scale and is also applied to gas release at large ocean depths to study the validity of the model for realistic scenarios.