Maarg Manthan · Topic 21.5

Unconventional Gas – Coalbed Methane, Shale Gas and Tight Gas

Geography › Mineral and Energy Resources · Topic 21.5

Unconventional gas is natural gas trapped in rocks from which it does not flow freely, so it needs special methods such as hydraulic fracturing to be extracted. It includes coalbed methane, held in coal seams, shale gas, held in fine-grained shale, tight gas, held in low-permeability sandstone, and gas hydrates in the sea floor. The United States led a shale revolution; India has produced coalbed methane in small amounts but has no commercial shale gas yet.

5 min read · UPSC Prelims · Geography · Mineral and Energy Resources

At a Glance

Coalbed methane Gas in coal seams; Raniganj, Jharia, Sohagpur
Shale gas Gas in shale; needs fracking
Tight gas Gas in low-permeability sandstone
Gas hydrates Gas frozen with water; Krishna–Godavari, Mahanadi
Leader United States, shale revolution
Exam link UPSC Prelims, Geography: Mineral and Energy Resources

Where Does It Fit?

This is the fifth topic of the macro on mineral and energy resources. The previous topic described conventional natural gas, and this one covers gas from harder sources. The next topic begins the metallic minerals with bauxite. Previous topic: Natural Gas and the Petroleum-Gas Value Chain. Next topic: Bauxite and Aluminium.

What Are the Unconventional Gases?

Type	Where the gas is held	How it is obtained
Coalbed methane	Adsorbed on the surfaces of coal seams, mostly methane	Water is pumped out of the seam to lower the pressure, so that the gas is released and flows up the well; usually shallower and cheaper than shale gas
Shale gas	Trapped in fine-grained, organic-rich shale, which is both the source rock and the reservoir	Horizontal drilling plus hydraulic fracturing, or fracking, in which water, sand and chemicals are injected at high pressure to crack the rock
Tight gas	In sandstone or limestone with very low permeability	Fracking and horizontal wells
Gas hydrates	Methane trapped in ice-like crystals with water in cold, high-pressure sea floor and permafrost sediments	Still at the research and pilot stage; heating or depressurising the deposit releases gas

Conventional gas, as in Natural Gas and the Petroleum-Gas Value Chain, collects in porous reservoirs under a cap rock and flows when a well is drilled. Unconventional gas is spread through tighter rocks, so it takes many more wells and more energy per unit of gas.

What Is the Position of the World and India?

Shale revolution: the United States combined horizontal drilling and fracking from the 2000s, which turned it from an importer of gas into the world’s largest producer and an exporter of LNG, with the Marcellus, Barnett, Eagle Ford and Permian shale plays. China, Argentina (Vaca Muerta), Canada and Australia also have large shale resources.
Coalbed methane in India: India has large coalbed methane resources, estimated at several trillion cubic metres in the Gondwana coalfields of Jharkhand, West Bengal, Madhya Pradesh, Chhattisgarh and Odisha. The Raniganj South block in West Bengal, Jharia, Bokaro and Sohagpur in Madhya Pradesh are important, and commercial production began at Raniganj in 2007, but output is small, only a fraction of a million cubic metres a day nationally, because of delays and high costs. The policy of 1997 and bidding rounds gave blocks to ONGC, Reliance and private firms.
Shale gas in India: the basins of Cambay, Krishna–Godavari, Cauvery, the Damodar valley and Assam have shale of potential. The shale gas and oil policy of 2013 allowed state firms ONGC and Oil India to explore in their areas, and the Hydrocarbon Exploration and Licensing Policy of 2016 offered blocks for all hydrocarbons under a single licence, but there is no commercial shale gas production yet.
Gas hydrates: India has surveyed gas hydrates under the National Gas Hydrate Program, with discoveries in the Krishna–Godavari, Mahanadi and Andaman offshore areas, and a deep-sea mission to explore them is in progress. The recoverability and economics are not yet proven.

What Are the Issues?

Water use and pollution: fracking needs millions of litres of water for each well, and the return fluid, with chemicals, must be treated and may pollute groundwater if wells leak.
Earth tremors: injecting waste water deep underground has caused small earthquakes in some regions.
Methane leakage: leaks of methane, a powerful greenhouse gas, reduce the climate benefit of gas over coal.
Land and people: thousands of wells need land in densely populated regions such as the Indian plains.
Cost and geology: Indian shale is often deeper and clayey, with the rig fleet and water supply limited, so costs are higher than in the United States.

As an analytical point, the American model cannot be copied directly in India, which has less empty land, less water and a different property regime, as the owner of surface land does not own the minerals below. Coalbed methane, which is found in coalfields where mining is already done, and offshore gas hydrates are more promising pathways, but both need a stable policy, tested technology and clear environmental rules, as in Mining and Quarrying.

Why Is This Topic Important?

Terms CBM, shale, tight gas asked
Current affairs Hydrates and fracking
Environment Water and methane

What Came Next?

The next topic begins the metallic minerals with bauxite and aluminium. Next topic: Bauxite and Aluminium.

Key People and Terms

Coalbed methane Gas in coal seams
Shale gas Gas in shale rock
Tight gas Gas in low-permeability rock
Fracking Hydraulic fracturing of rock
Gas hydrate Methane ice in sea floor
Play Area of shale with potential

Exam Corner

Points to Remember

CBM is in coal seams; water is pumped out first.
Shale needs horizontal drilling and fracking.
Raniganj had the first Indian CBM production, 2007.
Hydrates: Krishna–Godavari, Mahanadi, Andaman.
No commercial shale gas in India yet.

Do Not Confuse With

Shale gas and shale oil Gas versus oil from the same kind of rock
Shale gas and tight gas In shale versus in tight sandstone
CBM and coal gasification Gas already in the seam versus gas made from coal

Memory Hook

Coal seam, shale, tight sand, ice crystals: crack the rock or drop the pressure to set the gas free.

Mains Angle

Questions ask about potential and concerns. These points add depth.

Potential Resources in basins
Concerns Water, leaks, land
Way ahead CBM and hydrates

A Question You May Face

An original practice question, not a past paper question.

“What is unconventional gas? Discuss the prospects and environmental concerns of shale gas and coalbed methane in India.”

How to Answer

Define Types of gas.
World United States example.
India Basins and policy.
Concerns Water, methane, land.

GS Relevance

Prelims: definitions, hydraulic fracturing, CBM blocks and shale basins of India, gas hydrates. GS Paper 3: energy security, environmental concerns of fracking.

Frequently Asked Questions

What is unconventional gas?

Unconventional gas is natural gas that is held in rocks from which it does not flow easily, so special methods such as hydraulic fracturing or dewatering are needed. It includes coalbed methane, shale gas, tight gas and gas hydrates, unlike conventional gas that flows from porous reservoirs.

What is coalbed methane?

Coalbed methane is natural gas, mostly methane, adsorbed on the surfaces of coal in underground seams. To extract it, water in the seam is pumped out to lower the pressure, which lets the gas flow to the surface. India has resources in the Gondwana coalfields, such as Raniganj, Jharia and Sohagpur.

What is hydraulic fracturing?

Hydraulic fracturing, or fracking, is a method of injecting water mixed with sand and chemicals at high pressure into a well to crack the rock and release trapped gas or oil. It is used with horizontal drilling for shale gas and tight gas, but raises concerns over water use and pollution.

Does India produce shale gas?

India has shale in basins such as Cambay, Krishna–Godavari, Cauvery and the Damodar valley, and policies since 2013 allow exploration, but commercial shale gas production has not started. Challenges include deep, clayey shale, limited water, high cost and environmental and land concerns.

What are gas hydrates?

Gas hydrates are ice-like crystals in which methane gas is trapped within water molecules, found in cold, high-pressure sediments of the deep sea floor and in permafrost. India has identified deposits off the Krishna–Godavari, Mahanadi and Andaman coasts, but methods for economic recovery are still being tested.

PYQ Practice — Statement Analysis

1 Fracking is used to extract shale gas.

True

It cracks the rock with fluid at high pressure.

2 Coalbed methane is extracted by pumping water out of coal seams.