Far from dismissing this potential new energy source off hand, all risks need to be assessed first, before grand scale exploitation should be considered. Here a few pointers to articles highlighting the risks.
[cbc.ca] – Methane hydrates: Energy’s most dangerous game (October 2008)
Meet methane hydrates, the world’s most promising and perilous energy resource… Methane is the principal component of natural gas, and massive amounts of it are trapped in reservoirs beneath the sea floor and under a layer of the ice-like substance. The scale of the resource is spectacular. By some estimates, methane hydrates contain more energy content than all other known fossil fuels combined… Methane hydrates are frozen water molecules that trap methane gas molecules in a crystalline, lattice-like structure known as a hydrate. Unlike normal ice, hydrate ice literally burns — light a match and it goes up in flames. As temperatures rise or pressure rates fall, the hydrate disintegrates and the water releases the gas… A substantial amount of evidence suggests that weakening the lattice-like structure of gas hydrates has triggered underwater landslides on the continental margin. In other words, the extraction process, if done improperly, could cause sudden disruptions on the ocean floor, reducing ocean pressure rates and releasing methane gas from hydrates. A mass release of methane into the sea and atmosphere could have catastrophic consequences on the pace of climate change. More than 50 million years ago, undersea landslides resulted in the release of methane gas from methane hydrate, which contributed to global warming that lasted tens of thousands of years.
[science.howstuffworks.com] – How Frozen Fuel Works
The potential rewards of releasing methane from gas hydrate fields must be balanced with the risks. And the risks are significant. Let’s start first with challenges facing mining companies and their workers. Most methane hydrate deposits are located in seafloor sediments. That means drilling rigs must be able to reach down through more than 1,600 feet (500 meters) of water and then, because hydrates are generally located far underground, another several thousand feet before they can begin extraction. Hydrates also tend to form along the lower margins of continental slopes, where the seabed falls away from the relatively shallow shelf toward the abyss. The roughly sloping seafloor makes it difficult to run pipeline.
[japantimes.co.jp] – Methane hydrate energy solution?
Raw methane released into the atmosphere produces a greenhouse effect 25 times more potent than carbon dioxide. So every effort must be made to ensure it doesn’t leak during extraction. MH21 says the decreasing-pressure method lessens the risk because the lower pressure in the wells allows gas released by methane hydrate under the seabed to flow up naturally, giving it little chance to escape. It has also been noted, however, that when methane hydrate decomposes, it can trigger landslides as the decomposing layer disappears, warping the seafloor. The impact of submarine landslides is still being studied, but they are known to occur on slopes. MH21 plans to drill only in flat layers until further studies shed more light on the risks.