How are gas hydrates formed?
Unlike conventional natural gas, the methane in gas hydrates is largely the result of anaerobic bacteria acting on organic matter in the sediments below the sea floor. In areas of low sedimentation rates, low organic content and high oxygen content, aerobic bacteria acting on the organic matter generate carbon dioxide. However, where the sedimentation rate and organic content are high, the environment becomes anoxic (deficient in oxygen) at shallow sediment depths and anaerobic bacteria acting on organic matter generate methane. In certain of these environments, low temperature and high pressure act in concert to create the frozen hydrates. Gas hydrates occur naturally where combinations of temperature and pressure favour the stability of gas hydrate over a gas-water mixture. As shown in the diagrams, both temperature and pressure increase with depth. The stability of gas hydrates increases with increasing temperature and pressure, but not as quickly as the rate at which temperature in
