The Indian Institute of Technology Madras (IITM) on Tuesday said its researcheers are developing new techniques for extracting methane from natural gas hydrates.
In a statement issued here, IITM said promising results from their research have been published recently in leading international journals such as Energy and Fuels and Applied Energy.
According to IITM, there has been worldwide interest in the development of techniques to extract methane gas trapped in ice-like crystalline cages called 'gas hydrates', which are present in shallow sediments along continental coastlines.
"Hydrates are particularly promising methane sources in India because nearly 1,900 trillion cubic meters of methane gas lie untapped in these cages within the waters of the Indian Exclusive Economic Zone," IITM said.
According to the institute, this methane is 1,500 times more than the country's current gas reserves. The Ministry of Earth Sciences reports that Krishna-Godavari and Andaman basins have large amounts of gas hydrates.
The IIT Madras research towards developing techniques to extract methane from gas hydrates can enable indigenous supply of natural gas and potentially lighten the nation's natural gas import burden, the statement said.
The research is being headed by IITM Department of Ocean Engineering Professor (Petroleum Engineering) Jitendra Sangwai who studies state-of-the-art processes used to recover crude oil from offshore reservoirs in India. The other members of the research team are Pawan Gupta and Vishnu C.
The research is being funded by IITM and Department of Science and Technology (DST).
"Research is underway around the world to develop methods to extract methane from gas hydrates from both clayey and sand-dominated reservoirs. The Krishna-Godavari basin is a clayey reservoir while the off-shore Indian peninsular ones are a mix of both clayey and sandy.
"As gas hydrates are comparatively immobile and impermeable, they need to be dissociated into their constituent gas and water before the methane recovery from hydrate reservoirs is possible," Sangwai was quoted as saying in the statement.
Four techniques are being studied in various laboratories for this dissociation - thermal stimulation, depressurisation, chemical injection and carbon dioxide injection.
Sangwai's team analyses the combined effects thermal stimulation and depressurisation in one branch of study, and polymer injection in another.
In their study on thermal stimulation and depressurization, the IITM research team reported that the combination of the two processes is more efficient for methane production from clayey hydrate reservoirs than either soil types, individually.
This has been attributed to the relatively faster increase in volume available for the gas to expand upon application of heat, which results in faster decrease in pressure of the hydrate reservoir.
For the depressurisation process alone, the researchers also found that multi-step depressurisation is more efficient than the single-step depressurisation.
Depressurisation is the most energy-efficient production approach for extracting gases from clayey hydrates and is possibly the most likely technology to mature in the near future, the statement said.
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