Over the last few months, several articles and papers have emphasized the potential role shale gas will play in India's hunt for energy. Shale gas is natural gas trapped in fine grained sediment. These articles did not have any graphics so I am putting up a map of Indian sedimentary basins and a graphic depicting shale gas geological reservoirs.



Indian Sedimentary Basins




Source: Geotimes

The basins of interest in terms of shale gas potential are the mostly marine Mesozoic and Cenozoic basins in Rajasthan and Gujarath and the Cenozoic basins of Assam. The Gondwana basins of central and eastern India are continental interior rift basins and are coal rich and have associated coal bed methane which if tapped could also play an important role in India's energy mix.


Shale Gas Geological Reservoirs




Unlike gas reservoirs in coarser materials like sands, natural gas in shale is trapped in micro pores which may not be connected to each other i.e. they have low permeability and the gas is quite difficult to extract.


India's conventional natural gas reserves are growing with new discoveries mostly along the east coast Krishna Godavari offshore basins. Early estimates of these gas resources if proved correct may more than double in terms of energy equivalence India's proven reserves of about 5.6 billion barrels of oil. Unconventional resources like shale gas have the potential of adding substantially more to these resources. Currently natural gas makes up a small portion of India's energy consumption pie (see fig on left) and the chance to move towards a cleaner emissions profile by substantially displacing coal in power generation (coal makes up about 70% of electricity generation) and eventually as fuel for transport makes these unconventional sources a critical energy resource of the future.

I don't know how much shale gas resources India has because there has not been a systematic evaluation of shale gas. India's current energy policy prohibits exploitation of shale gas and coal-bed methane. The sooner that policy changes the better for energy starved India.

[Update Sept 3:] As a reader pointed out in the comments there is recent movement from the government on the exploitation of shale gas and coal bed methane. See this article. A policy on shale gas is likely to be out by next year, while the government has already auctioned of several blocks for exploration of CBM from various basins.

Still, there is one aspect of exploiting these resources that has not been touched upon by any of the articles I have come across and that is the environmental costs of extracting shale gas. Since this gas is locked up in impermeable layers one of the common methods of extracting it is by hydraulic fracturing of the rock. This involves injecting the shale with fluids and gels mixed with particulates like sand to keep the induced fractures open and enable migration of the gas along open fractures.

A new film "Gasland" discussed on Science Friday last month looks at some of the problems of hydraulic fracturing or "fracking" of the Marcellus shale that underlies large parts of Pennsylvania, New York and Ohio and West Virginia. Chemicals used in the injecting fluid has been reported to contaminate groundwater in Pennsylvania. At least according to the film, the energy companies have been less than forthright about the chemical composition of the injecting fluids which the film claims includes carcinogens and neurotoxins.

All this should send warning signals about the way and means by which India goes about exploiting these shale gas resources. Groundwater is as important a resource for India's economic development as is natural gas. Almost all drinking water needs in rural areas are met by groundwater. A significant majority, about 2/3, of arable area in India is irrigated by groundwater. Contamination of large portions of the overlying aquifer will be nothing short of a catastrophe for farmers who have no other water supply but groundwater.

The exploitation of coal bed methane offers another avenue for social conflict. The Gondwana basins which are coal rich are forested regions and home to many tribal communities. There has been a long history in India of the government and private mineral companies riding roughshod over tribal rights. The current violent insurgency that is taking place along tribal regions of Chattisgarh, Maharashtra and Jharkhand has its roots in the rampant exploitation and callous indifference shown by the state and private companies towards tribal communities.

So, shale gas and coal bed methane offer a significantly large energy source but also open up the possibility of more environmental and social disruption.