Journal of Petroleum Geology, vol. 21(3), July 1998, pp. 343-357

OCEANIC METHANE HYDRATE: THE CHARACTER OF THE BLAKE RIDGE HYDRATE STABILITY ZONE, AND THE POTENTIAL FOR METHANE EXTRACTION

M. D. Max* and W. P. Dillon

Oceanic methane hydrates are mineral deposits formed from a crystalline "ice" of methane and water in sea floor sediments (buried to less than about 1 km) in water depths greater than about 500 m; economic hydrate deposits are probably restricted to water depths of between 1.5 km and 4 km. Gas hydrates increase a sediment's strength both by "freezing " the sediment and by filling the pore spaces in a manner similar to water-ice in permafrost. Concentrated hydrate deposits may be underlain by significant volumes of methane gas, and these localities are the most favourable sites for methane gas extraction operations. Seismic reflection records indicate that trapped gas may blow-out naturally, causing large-scale seafloor collapse.