Unconventional Gas Reservoirs, Coalbed Methane, Shale Gas Reserves in India | UPSC Notes

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Unconventional Gas Reservoirs

  • Conventional reservoirs of oil and natural gas are found in permeable sandstone.
  • Unconventional Gas Reservoirs occur in relatively impermeable sandstones, in joints and fractures or absorbed into the matrix of shales [Shale is Sedimentary Rock], and in coal.
  • Given current economic conditions and state of technology, they are more expensive to exploit.
  • Example: Tight gas, shale gas, and coalbed methane.
Unconventional Gas Reservoirs
Unconventional Gas Reservoirs UPSC

Coalbed Methane

  1. Considerable quantities of methane is trapped within coal seams.
  2. A significant portion of this gas remains as free gas in the joints and fractures of the coal seam.
  3. Gas are adsorbed on the internal surfaces of the micropores within the coal itself.
  4. Extraction — pumping large quantities of water that saturate the seam. [water will occupy the gaps and pores and will push out the gas]
  5. Important source of natural gas.
  6. It contains —  very little heavier hydrocarbons —  propane or butane.
  7. The presence of this gas is well known from its occurrence in underground coal mining, where it presents a serious safety risk.

Fire Accidents in Coal Mines are mainly due to Coalbed Methane, and Lignite deposits which undergo spontaneous combustion.

Coalbed Methane India (CBM)

  • India holds significant prospects for commercial recovery of coal-bed methane.
  • The country has an estimated 700-950 billion cubic metre of coalbed methane.
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Problems — Exploration, Extraction of CBM

  1. No right for private participation in exploration of CBM or Shale
  2. Lack of inter-ministerial coordination — Petrol Ministry v/s Coal
  3. Capital Intensive | not much profitable
  4. Technological incapabilities | weak org. Setup
  5. Restrictive laws
  6. Complicated Gas pricing in India 

Shale Gas 

  • Shales are fine-grained sedimentary rocks formed of organic-rich mud at the bottom of ancient seas.
  • Action of heat and pressure
  • Over time — migration of gases to nearby SS — becomes conventional gas
  • Shale Gas —  locked in the nonporous shale | formation and storage at the same place

Shale Gas Reserves Across the World

Shale Gas Reserves Across the World

Shale Gas Reserves in India

Shale Gas Reserves in India
  • Cambay (GJ), Assam-Arakan Basin, KG Basin 
  • Tech involved — Hydraulic Fracking 
    • Need lots of water and land and Gaur Gum (expensive shit)
  • Environmentalists have objected to fracking because of the damage to forest cover and possible contamination of ground water.
  • One estimate by Indian scientists places potential reserves at as high as 527 tcf.
Problems Associated With Shale Gas

Problems Associated With Shale Gas Exploitation

  • Environmental Hazards | GW contamination | Forest damage 


  • All the water required must be obtained from rain water harvesting.
  • Recycling and reusing of water 
  • Enforcing clear and practical legislation on environmental and water issues.

Shale Gas: Low Potential, High Risk and a Better Alternative 


  • India’s shale resources at a more modest 65 trillion cubic feet. India’s CBM potential is estimated at 450 tcf.       450 vs 65 !
  • So, focus must be on CBM exploration rather than on risky shale business.

Mains 2013 Questions

It is said that India has substantial reserves of shale oil and gas, which can feed the needs of the country. However, tapping of resourced does not appear to be high on the agenda. Discuss critically the availability and issues involved. (10 marks – 200 words)