Eulerian large-eddy simulations of deep-sea hydrocarbon plumes with hydrate formation and decomposition

In the case of a deep-sea oil spill incident, the gas bubbles, oil droplets, and entrained seawater form a multiphase hydrocarbon plume and rise together towards the sea surface through stratified seawater. Below the thermodynamic equilibrium depth, the natural gas molecules inside the bubbles can react with the surrounding seawater to form solid hydrate shells outside the bubbles. With sufficient reaction time, gas bubbles can even become solid hydrate particles completely. As the hydrate-covered gas bubbles and hydrate particles reach the thermodynamic equilibrium depth, hydrate decomposition occurs and gas molecules are dissolved into the surrounding seawater. The hydrate formation and decomposition can change the buoyancy force that drives the plume, resulting in considerable effects on the plume dynamics. In this study, an Eulerian large-eddy simulation model is developed to simulate the hydrocarbon plumes with the effects of hydrate formation and decomposition. Two different scenarios with the gas releasing depths of 630m and 1000m are modeled and the corresponding plume characteristics are analyzed.