Washington  - Drillers have found possibly large deposits of a crystalline form of methane called gas hydrates in rocks and sands on the floor of the Gulf of Mexico, the US Geological Survey said Friday.

The USGS said in a statement that the Gulf contains "very thick and concentrated gas-hydrate-bearing reservoir rocks, which have the potential to produce gas using current technology."

The agency did not give an estimate of how much gas could be recovered from the test area, nor what the potential for energy production would be.

The drilling was managed by Chevron off the US shore.

Gas hydrates are crystalline solids made of methane gas molecules surrounded by a cage of water molecules. They look "very much like water ice," the USGS said on its website.

They harbour an "immense carbon reservoir" that has "major implications" not only as an unconventional energy resource but also as a hazard for the climate as a greenhouse gas, the USGS said.

The USGS estimated that there is twice as much carbon bound in gas hydrates worldwide as is found in all other known fossil fuels on Earth.

The USGS has also found large accumulations of gas hydrates off the coast of North Carolina and South Carolina.

In drilling in the Gulf of Mexico, the project found sand reservoirs between 15 and 30 metres thick containing gas hydrates.

"These sites should provide a wealth of opportunities for further study and data collection that should provide significant advances in understanding the nature and development of gas hydrate systems," USGS scientist Timothy Collett said.

The USGS called it an "exciting discovery" because for the first time in the Gulf of Mexico, scientists were able to predict the location of the hydrates before drilling. (dpa)