What are methane hydrates

Methane hydrate

There are some unconventional energy sources that are associated with high environmental risks and also relatively expensive to mine. These include oil sands and oil shale, shale oil and shale gas, and methane hydrate. Oil sands have been included in the oil reserves and oil resources since 2002, and oil shale is included in the oil resources. Methane hydrate has not found its way into the reserves or into the resources for a long time, although there is constant speculation, see newspaper Die Welt, that it is the largest fossil energy source, the carbon content of which could exceed the sum of all other fossil energy sources. There is no reliable information about the size of the deposits. A non-speculative but uncertain value is given in the BGR's 2019 energy study, according to which gas hydrate (methane hydrate) is a gas resource with an occurrence of 184 × 1012 m3 still below the estimated shale gas occurrence of 205 × 1012 m3 lies. Hydraulic fracturing as a technical process is controversial, but it is widely used in the USA and other countries. Regarding methane hydrate, so far only test funding of 300,000 m3 from May to July 2017 at a depth of 1266 m in the South China Sea near the Chinese coast. The publication reports on advances in the safety control of the production process, but says nothing about future methane hydrate recovery. Japan also has a research program to investigate the possibilities of generating energy from methane hydrate deposits. The MH21 project provides for research work, but not yet the start of commercial funding.

Methane hydrate is described on the gas hydrate pages of the Helmholtz Center for Ocean Research Kiel, GEOMAR. The funding problem is particularly addressed on the WorldOceanReview website. The methane was produced by bacteria in the oceans. They have converted the dissolved carbon dioxide into methane or degraded marine biomaterial. If methane hydrate is formed, water must be supersaturated with gas and certain pressure and temperature conditions must prevail.


High pressures and low temperatures are also necessary for the stability of the methane hydrate. If the stability conditions are violated by environmental influences, methane can be released in large quantities. Since it has 25 times the effect of carbon dioxide, it would cause a huge greenhouse effect.

The left picture from Wikipedia shows the white methane hydrate, which burns with a red-yellow flame, whereby water drips down, and of course carbon dioxide is produced. The top left shows the dome model of a methane gas molecule.

The unit cell of the cubic crystal structure consists of eight ice cages in which water molecules (red oxygen atoms and white hydrogen atoms) are connected to one another via hydrogen bonds. One methane molecule is built into each of the ice cages. The stoichiometric formula is 8 CH4 46 H.2O.

 

 


Last change: 01.09.2020