Methane hydrates: Fluctuation in time
Climate time scales and month-long field trials
What this tab covers How availability changes over seconds, days, seasons, years and longer, how predictable it is, and what that means for the plants that use it.Hydrate deposits change on climate time scales as ocean temperature and sea level shift. As an energy supply they exist so far only as short field tests.
Variation by time scale
| Time scale | What happens | How large |
|---|---|---|
| Climate (decades to millennia) | The stability zone shifts with bottom-water temperature. Thin deposits at the edge of stability are the most sensitive.4 | Hydrate is likely dissociating now on upper continental slopes, which hold about 3.5% (63 Gt of carbon) of the inventory |
| Natural release today | Most methane released by dissociation is consumed in sediments and water before reaching the air.4 | About 5 to 6 Tg CH4 per year assumed in IPCC budgets, about 1% of the 555 Tg total methane flux |
| Field tests (days to weeks) | Offshore tests in Japan's Nankai Trough produced gas for days to weeks before sand and water problems.9 | 119,500 cubic metres in 6 days (2013); about 35,000 in 12 days and about 200,000 in 24 days (2017) |
| Field tests (weeks to months) | Chinese tests in the South China Sea ran longer at higher rates.9 | Over 309,000 cubic metres in 60 days (2017); 861,400 cubic metres in 30 days, 28,700 per day (2020) |
| Next step | A long-term onshore test in Alaska aims to measure reservoir response over most of a year.9 | Planned 9 to 12 months, reported to have started in October 2024 |
How predictable it is
Not yet meaningful as a supply. Test production rates are low and uncertain, and no commercial production exists. Natural dissociation responds slowly and fairly predictably to ocean warming.
There is no production record yet, only tests. The best result so far, 28,700 cubic metres a day for a month in 2020, would supply about 0.4 PJ a year if sustained (calculated). That is a tiny amount next to world gas output of about 4,100 bcm a year. The time scale that matters for hydrate as a resource is therefore the decades needed to show stable long-term flow and acceptable costs.
On climate time scales the deposits are dynamic. Ocean warming slowly moves the edge of the stability zone, and the upper-slope deposits there are already thought to be dissociating.
Sources
- The interaction of climate change and methane hydrates (Ruppel and Kessler), Reviews of Geophysics 55 American Geophysical Union, 2017
- Gas hydrate energy research: 2024 update USGS, 2024