A METHOD OF HARVESTING GAS HYDRATES FROM MARINE SEDIMENTS Zhang, Hong-Quan; Brill, James P.; Sarica, Cem
Gas hydrates bind immense amounts of methane in marine sediments. If produced cost effectively, they can serve as a stable energy supply. No viable technologies for extracting gas hydrates from deep ocean deposits have been developed to date. Due to the shallow depths, low hydrate concentration, low permeability of the gas hydrate stability zone, lack of driving pressure and the slow melting process, low productivity is anticipated for gas production from gas hydrates in marine sediments. Therefore, only a large number of low cost wells can support an offshore production facility and pipeline transport to shore. The method of harvesting natural gas from sea floor gas hydrates presented in this paper is a combination of several new concepts including electrically adding heat inside hydrate rich sediments to release gas, using an overhead receiver to capture the gas, allowing gas to form hydrates again in the overhead receiver, and lifting produced hydrates to warm water to release and collect gas. This approach makes the best use of the nature of hydrates and the subsea pressure and temperature profiles. Consequently, it leads to a simple and open production system which is safe, economical, energy efficient, environmentally friendly, and without significant technical difficulties. Basic analyses and calculations on the feasibility and heat efficiency of the proposed method are presented and discussed.
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