"The vast deepwater methane hydrate deposits of the Gulf of Mexico are an open secret in big energy circles. They represent the most tantalizing new frontier of unconventional energy — a potential source of hydrocarbon fuel thought to be twice as large as all the petroleum deposits ever known.
For the oil and gas industry, the substances are also known to be the primary hazard when drilling for deepwater oil.
Methane hydrates are volatile compounds — natural gas compressed into molecular cages of ice. They are stable in the extreme cold and crushing weight of deepwater, but are extremely dangerous when they build up inside the drill column of a well. If destabilized by heat or a decrease in pressure, methane hydrates can quickly expand to 164 times their volume.
Survivors of the BP rig explosion told interviewers that right before the April 20 blast, workers had decreased the pressure in the drill column and applied heat to set the cement seal around the wellhead. Then a quickly expanding bubble of methane gas shot up the drill column before exploding on the platform on the ocean's surface."