The drilling danger of releasing giant bubbles of methane gas
The "burps of death" are what can ensue when drillers mess with the planet's least accessible stores of natural gas.
The trouble with gas hydrates, as those ice-like deposits in the Arctic and under ocean beds are known, is that they lock up high concentrations of methane in a notoriously unstable crystalline lattice.
Change the temperature and pressure just a bit, and the whole thing collapses, releasing giant bubbles of potentially explosive methane gas in a fit of geological indigestion.
Some scientists theorise that a global firestorm resulting from one such outburst may have barbecued the dinosaurs. Another ancient oceanic burp, which did not ignite, may have triggered an equally lethal spurt of global warming linked to mass extinctions.
Now Japan, which imports its entire gas supply, is stepping up efforts to exploit large deposits of methane gas hydrate off its earthquake-prone Pacific coast.
By the end of next year, the state-owned Japan Oil, Gas and Metals National Corporation (Jogmec) hopes to supervise drilling tests on hydrates located in the eastern Nankai trough off central Japan. The hitherto intractable gas deposits lie just under the seabed in water depths of up to 1,400 metres.
Jogmec called late last year for proposals for the production test, in the hopes of launching the project this spring.
If successful, it would be a worldwide first. A controlled flow of methane, the main fuel constituent of natural gas, has never been achieved from an offshore hydrate deposit. It has been demonstrated only once onshore. That was last November by a team of Japanese and Canadian researchers working in the Canadian Arctic, on the shores of the Beaufort Sea.
In a landmark experiment near the site of Canada's first Arctic offshore oil production, the team coaxed a well drilled 1,300 metres into permafrost to release a controlled flow of gas for six days. In the Arctic midwinter, the flame from the flared gas was clearly visible across the tundra, signalling the singular achievement.
"The message is quite clear. You can produce gas hydrates using conventional techniques," said Dr Scott Dallimore, a senior scientist at the Canadian government's department of natural resources, which co-led the experiment.
Previous attempts to produce gas from the Arctic's vast hydrate stores had succeeded for only a few hours at a time. The next challenge, said Dr Dallimore, was to prove it could be done safely for stretches of months or years.
Jogmec hopes to develop a safe, commercial offshore production process by 2018, a challenging target that if met could make the world's third-biggest economy far less dependent on gas imports.
The Earth's biggest known gas hydrate deposit lies deep in the Arabian Sea between India and Oman. That could have interesting ramifications for various countries in the region that are chronically short of gas.
Published: March 27, 2011 04:00 AM