Modeling the impact of an accidental release of methane gas in deepwater

A model to simulate the transport and fate of methane gas released in deepwater is presented. Methane gas when released in deepwater undergoes a series of physical chemical processes as it rises through the water column from the sea bed to the water surface. In the high pressure and low temperatures that are typical in the deepwater, methane gas is likely to be converted to hydrates. These hydrates will be dissociated back to gas when they reach lower pressures and higher temperatures in the shallower regions. When a large amount of methane is released it is likely to form a plume. The model presented here takes the plume thermodynamics and hydrodynamics into account in addition to the physico-chemical processes associated with gases and hydrates. This model considers the hydrate formation/dissociation, gas dissolution, hydrate dissolution, gas bubble break-up and coalescence, and the change of gas bubble size due to pressure and temperature changes. This paper presents the model formulation, simulations of ldquoDeepspillrdquo experiments and the comparison of the model results with experimental results.