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Methane Hydrate: What are ‘gas hydrates’?

Recent research has found that the methane hydrate deposits located in the Krishna-Godavari basin are of biogenic origin. The methane hydrate deposit in the Krishna-Godavari basin is a rich source that will ensure adequate supplies of methane, a natural gas.

Methane Hydrate

Details 

Methane is a clean and economical fuel. It is estimated that one cubic meter of methane hydrate contains 160-180 cubic meters of methane. Even the lowest estimate of methane present in the methane hydrates in KG Basin is twice that of all fossil fuel reserves available worldwide.

What is ‘methane hydrate’?

Methane hydrate is formed when hydrogen-bonded water and methane gas come into contact at high pressures and low temperatures in oceans.

What are ‘gas hydrates’?

  • They are formed when a gas such as methane gets trapped in well-defined cages of water molecules forming crystalline solids. It is a solid ice-like form of water that contains gas molecules in its molecular cavities.
  • Natural gas hydrates occur on continental margins and shelves worldwide from Polar Regions to the tropics.
  • Gas hydrate reservoirs are generally associated with biologically rich cold seep ecosystems at the seafloor. Cold seeps are locations where hydrocarbon-rich fluid seeps up from below the sea floor, often as methane or hydrogen sulphide.
  • It is estimated that total amount of carbon in the form of methane hydrates, far exceeds the carbon content in all the fossil fuel reserves put together and hence these are supposed to be the future potential energy resource.
  • Combustion of methane, is more CO2 efficient than that of any other hydrocarbon. Hence, using methane from gas hydrate compared to other hydrocarbons is relatively climate friendly. 
  • According to the latest estimates of the US Geological Survey, India has the second largest gas hydrate reserves after America. The Krishna-Godavari (KG), Cauvery and Kerala basins alone have 100-130 trillion cubic feet of estimated reserves.

Extraction of gas hydrates 

  • The natural gas from gas hydrate can be produced via –
    • Depressurisation – Drilling of hole into the layer of hydrate and reducing the pressure beneath. This technique is implemented for hydrates only in polar regions beneath the permafrost.
    • Thermal stimulation – via steam injection, hot brine solution etc. that raises the temperature of the local reservoir outside the hydrate region to cause the dissociation of the hydrate, thus releasing free gas which can be collected. 
  • However, no country in the world has so far developed the technology to produce gas hydrates commercially and economically. 
  • Gas hydrates are also important for seafloor stability studies, because “melting” gas hydrate may cause seafloor “land” slides. Methane released from gas hydrate may therefore play a significant role in climate change.