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The SEG Wiki page on Hydrates is being edited by William Vinson (UH) and will be completed by Nov 3rd.

File:Burning hydrate inlay US Office Naval Research.jpg
Gas hydrates are trapped physically within crystalline molecules.

Hydrates are methane gas molecules trapped in ice-like crystals of water. The temperature and pressure conditions of stability for this case commonly exists in deep water just beneath the sea floor.

A Brief History of Hydrates

Naturally-occuring gas hydrates were first discovered when anomalous high pressures restricted flow in natural gas pipelines[1][2]. A BSR (Bottom Simulating Reflector) is the first event from geophysical data that has been associated with identifying hydrates. This BSR exists on the Blake Outer Ridge along the eastern United States margin [3]. Discoveries with hydrate identification in the Blake Outer Ridge followed. Drilling into the BSR proved the existence of high methane contents, and further verified the association between BSR’s and hydrates[4]. Seismic velocities within the upper 600 meters were 2.0 to 2.2 km/s, and Stoll et al. (1971) suggested these anomalously high velocities to be a result of increased rigidity when methane is present in the sediment.[5] Seismic data also returned high amplitude responses there. It was later suggested that the high amplitude responses of the Blake Outer Ridge were caused by an accumulation of gas occurring at the base of the hydrated zone[6]. Tucholke et al. (1977) showed a strong correlation between the BSR and the pressure and temperature of the phase boundary in the methane + 3% NaCl + water system.[7]

  1. Deaton, W. M., and E. M.Frost, Jr., 1946, Gas hydrates and their relation to the operation of natural gas pipe lines: U.S. Bur. Mines Mon. 8, 101
  2. Hammerschmidt, E. G., 1940, Elimination of hydrate troubles: Oil and Gas Journal, 39, 61-68.
  3. Markl, R. G., G. M. Bryan, and J. I. Ewing, 1970, Structure of the Blake-Bahama Outer Ridge: Jour. Geophys. Research, 75, 4539-4555.    
  4. Hollister, C. D., et al, 1972, Initial reports of the Deep Sea Drilling Project, v. II: Washington, D.C., U.S. Govt. Printing Office, 1077
  5. Stoll, R. D., 1974, Effects of gas hydrates in sediments, in Natural gases in marine sediments: Marine Sci., 3, 235-248.
  6. Bryan, G. M., 1974, In situ indications of gas hydrate, in Natural gases in marine sediments: Marine Sci., 3, 299-308. 
  7. Tucholke, B. E., G. M. Bryan, and J. I. Ewing, 1977, Gas-hydrate horizons detected in seismic-profiler data from the western North Atlantic: AAPG Bull., 61, 698-707.