# Methane hydrates: How energy resides

How frozen cages pack in so much gas

Source page: https://www.materialinsights.org/energy/e_hydrates/resides/

What this tab covers The physical form in which the energy is held or carried, where it comes from, the chain of transformations that put it there, and how concentrated it is.

Methane hydrate is an ice-like solid in which water molecules form cages around methane, holding about 164 times its own volume of gas. It is stable only where it is cold and under pressure.
 Form Chemical energy of methane locked in a water-ice cage (clathrate) Origin Fossil solar (methane from buried organic matter, made by microbes or deep heating)

#### How it got there
 Fusion in the Sun Sunlight Photosynthesis, mostly by marine plankton Organic matter buried in sea-floor sediment Microbial or thermal generation of methane Methane meets cold, high-pressure pore water Water cages trap methane as solid hydrate

#### How concentrated it is

| Measure | Value | Note |
|---|---|---|
| **Gas released per volume of hydrate** | 164 cubic metres of methane (at standard conditions) per cubic metre of hydrate^[1](https://www.aapg.org/science/alternative-resources/gas-hydrates/resource/how-much-gas-is-trapped-within-gas-hydrate-accumulations) | For a cage 90% filled with gas. |
| **Energy per volume of pure hydrate** | about 6.3 GJ per cubic metre (calculated at 38.6 MJ per cubic metre of gas)^[1](https://www.aapg.org/science/alternative-resources/gas-hydrates/resource/how-much-gas-is-trapped-within-gas-hydrate-accumulations) | Roughly a quarter of LNG (about 23 GJ per cubic metre); real reservoirs are mostly sediment. |
| **Pore filling in the best sand reservoirs** | porosity 0.38 to 0.40, hydrate saturation over 80% fraction of rock and of pore space^[2](https://www.usgs.gov/centers/whcmsc/science/us-geological-survey-gas-hydrates-project?page=2) | Gulf of Mexico, Green Canyon block 955 cores. |
| **Minimum water depth for marine stability** | about 300 to 500 (USGS gives over about 350 m and 1,000 to 1,650 ft) m^[3](https://www.usgs.gov/news/gas-hydrate-breakdown-unlikely-cause-massive-greenhouse-gas-release) | In the Arctic, hydrate is also stable in and beneath permafrost on land. |

Hydrate forms where methane and water meet at low temperature and high pressure: in a layer up to several hundred metres thick beneath the sea floor on continental margins, and in and below Arctic permafrost. Most of it is spread thinly through clay-rich mud, which cannot be produced. The realistic energy targets are sand layers, such as buried channels, where hydrate can fill over 80% of the pore space.

To release the energy, the hydrate must first be dissociated, usually by lowering the pressure in a well (depressurisation) so the cages break down into gas and water. Then the methane is handled like natural gas. Because the solid is stable only within a narrow window, warming or depressurisation releases it, which is both the extraction method and the main environmental concern.

#### Sources

1. [How much gas is trapped within gas hydrate accumulations? (T. Collett)](https://www.aapg.org/science/alternative-resources/gas-hydrates/resource/how-much-gas-is-trapped-within-gas-hydrate-accumulations) AAPG Energy Minerals Division, 2000
2. [U.S. Geological Survey Gas Hydrates Project (project page, page 2)](https://www.usgs.gov/centers/whcmsc/science/us-geological-survey-gas-hydrates-project?page=2) USGS Woods Hole Coastal and Marine Science Center, 2024
3. [Gas hydrate breakdown unlikely to cause massive greenhouse gas release](https://www.usgs.gov/news/gas-hydrate-breakdown-unlikely-cause-massive-greenhouse-gas-release) USGS, 2017

## Other sections

- [Summary](https://www.materialinsights.org/energy/e_hydrates/index.md)
- [Overview](https://www.materialinsights.org/energy/e_hydrates/overview/index.md)
- [Correlation](https://www.materialinsights.org/energy/e_hydrates/correlation/index.md)
- [Abundance](https://www.materialinsights.org/energy/e_hydrates/abundance/index.md)
- [Fluctuation in time](https://www.materialinsights.org/energy/e_hydrates/time/index.md)
- [Across the Earth](https://www.materialinsights.org/energy/e_hydrates/geography/index.md)
- [Impact on nature](https://www.materialinsights.org/energy/e_hydrates/nature/index.md)
- [Relationships](https://www.materialinsights.org/energy/e_hydrates/links/index.md)