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How do methane hydrates form in polar regions and beneath the ocean floor?

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natural gas The Troll A natural gas production platform in the North Sea, 80 km (50 miles) northwest of Bergen, Norway. Troll A, the largest movable structure ever built, rests on the seafloor some 300 metres (990 feet) below the surface and rises more than 100 metres (330 feet) above the sea. The platform regulates the recovery of gas from 40 wells located on the seafloor.

Methane hydrates are unique molecular structures in which individual methane molecules are trapped within icy, cagelike lattices of water molecules. These structures form under very specific combinations of high pressure and low temperature, which allow methane to migrate into reservoirs containing water and stabilize into a solid hydrate form.12

In polar regions, these deposits are found beneath the permafrost. Beneath the ocean floor, they occur along the outer edges of continental shelves and slopes, typically at depths of roughly 1,650 feet (500 meters) or greater, where the necessary pressure and temperature conditions exist to keep the hydrates stable within the sediments.12

Because these reserves are located in extremely sensitive polar ecosystems and marine ecosystems, any potential extraction technology must be designed with the utmost care to prevent environmental damage.1