A model to simulate the transport and fate of gas and hydrates released in deepwater

Abstract

Methane and natural gas, if released in deepwater, undergo physico-chemical processes as they rise through the water column. In deepwater, these gases are likely to be converted into hydrates. These are dissociated into gas upon reaching shallower regions. The present model accounts for plume thermodynamics and hydrodynamics, and is integrated with the associated physico-chemical processes such as hydrate formation/dissociation, gas dissolution, hydrate dissolution, hydrate shell crumbling and reformation, heat and mass transfer inside gas bubbles, multiple-sized bubbles and their size change, and possible gas separation from the main plume. The model simulations compare well with field data from Deepspill in Norway, and the gas bubble releases off the California coast. The scenario simulations show that the inclusion of multiple bubble sizes impacts the model results. Inclusion of hydrate dissolution is also important for deepwater releases. Without hydrate dissolution, the results tend to overestimate the hydrocarbon mass that will reach the water near the surface.

Keywords:

• Deepwater blowout
• deepwater model
• gas hydrate
• hydrate dissolution
• methane plume
• natural gas plume

Acknowledgements

This work was primarily funded by the Engineering Advancement Association of Japan under a contract from the Research Consortium for Methane Hydrate Resources in Japan (http://www.mh21japan.gr.jp) supported by the Ministry of Economy, Trade, and Industry.