Natural gas hydrate is a crystallized ice-like substance, consisting of water and natural gas, with methane as the most common gas. Water molecules form cages through hydrogen bonding and encapsulate gas molecules. Natural gas hydrates are found in the earth under high pressure and low temperature where water and gas co-exist, typically in permafrost and sub- marine environments. Hydrates have been considered a nuisance in the petroleum industry, creating barriers in pipe lines, and effort has mainly been put into preventing hydrate formation. However, natural gas hydrates are in recent decades acknowledged as a potential energy resource for the future; even conservative estimates suggest 1015 m3 CH4 STP present within hydrate.

Several methane production scenarios are proposed: thermal-, chemical- and pressure reduction induced dissociation is available, although depressurization is considered the least costly option. The University of Bergen has since 2002 worked on a fourth alternative: exchange of CH4 molecules with CO2. Lab scale experiments have repeatedly shown CO2-CH4 exchange within sediments. These experiments led to a field trial test in Alaska, operated by ConocoPhillips, by utilizing CO2 injection as a production method. Similar procedures as in the field test were performed in the lab, creating repetitive data for analysis on lab scale. This paper reviews results from both the laboratory and field pilot and discusses challenges and mitigating measures related to production.

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