Gas hydrates

Gas hydrates are naturally existing, ice-like solids that form at high pressures and low temperatures in seafloor sediments, in permafrost grounds, and in very deep lakes. They have been identified worldwide, particularly along continental margins in water depths exceeding about 400m. They consist of a cage-like structure of water and gas molecules, where biogenic methane is the most common constituent. The global amount of methane stored in hydrate has been estimated to be in the order of all other fossil hydrocarbon reservoirs together, thus are considered as a potential future energy resource. However, of economic interest are rather local to regional-scale deposits with high gas hydrate concentrations. The release of methane in the atmosphere caused by destabilisation of the gas hydrate zone may have a severe climate impact, because methane is a more efficient greenhouse gas than carbon dioxide. Another aspect is the slope stability along continental margins. Gas hydrate that forms within the pore space compacts and stabilizes the seafloor. Changes in seafloor temperature and/or pressure may move the stability zone leading to the dissociation of gas hydrates which may risk submarine slope slides.

In Germany, gas hydrates have been intensively studied since the middle of the 90ies. At present, new technologies are developed within the joint research project SUGAR. The overall aim of SUGAR is to produce natural gas from submarine hydrate deposits and securely store carbon dioxide as CO₂ hydrate within he stability zone.

Links:

• www.gashydrate.de
  
• http://www.fz-juelich.de/ptj/geotechnologien/gashydrate
  
• http://www.sugar-projekt.de
  
• http://walrus.wr.usgs.gov/globalhydrate/refrena.html