Researchers from the Indian Institute of Technology, Madras, are developing new techniques for extracting methane from natural gas hydrates. Promising results from their research have been published in international journals such as Energy and Fuels and Applied Energy recently.
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 metres of methane gas lie untapped in these cages within the waters of the Indian Exclusive Economic Zone. This is 1,500 times more than the country’s present gas reserve.
The Union ministry of earth sciences reports that the Krishna-Godhavari basin and Andaman Basin have large amounts of gas hydrates. This IIT Madras research can enable indigenous supply of natural gas and potentially lighten the nation’s natural gas import burden.
The research is being headed by Jitendra Sangwai, professor (petroleum engineering), department of ocean engineering, IIT-Madras, who studies state of-art processes used to recover crude oil from offshore reservoirs in India, and includes research scholars Pawan Gupta and Vishnu C.
In their study on thermal stimulation and depressurisation, the IIT Madras research team reported that the combination of the two processes is more efficient for methane production from clayey hydrate reservoir than either, 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 multistep 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 near future.
It is believed that energy content of methane occurring in a hydrate form is immense, possibly exceeding the combined energy content of all other known fossil fuels. “Controlled extraction of methane from gas hydrates can not only meet the enormous demand for energy all over the world but can also reduce detrimental geological release of greenhouse gas into the environment from these sources”, Sangwai said.
Development of emerging techniques for controlled extraction of methane from hydrates entails concerted efforts between academic, government and industrial laboratories and can potentially lead the country towards self-sufficiency in the energy sector.