With reference to two non-conventional energy sources called 'coalbed methane' and 'shale gas', consider the following statements : 1. Coalbed methane is the pure methane gas extracted from coal seams, while shale gas is a mnixture of propane and butane only that can be extracted from fine-grained sedimentary rocks 2. In India, abundant coalbed methane sources exist, but so far no shale gas sources have been found. Which of the statements given
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- A1 only
- B2 only
- CBoth 1 and 2
- DNeither 1 nor 2
Show answer
Answer: (D) Neither 1 nor 2
Both statements are wrong.
Statement 1 error:
Shale gas is NOT a mixture of propane and butane only.
Shale gas is mainly methane (natural gas) trapped in shale rock formations, along with small amounts of ethane, propane, and butane.
Coalbed methane IS methane from coal seams — that part is roughly correct, but the shale gas description is completely wrong.
Statement 2 error:
India HAS identified shale gas sources — notably in the Cambay Basin (Gujarat), Krishna-Godavari Basin, Cauvery Basin, and Damodar Valley.
So the claim that 'no shale gas sources have been found' is false.
India has significant unconventional gas reserves - coalbed methane in coal-rich states and shale gas in basins like Cambay and Krishna-Godavari.
Both coalbed methane and shale gas are primarily methane, not different hydrocarbon mixtures as the question tries to confuse students.
The question tests whether students can distinguish between the extraction source (coal seams vs shale rock) and the actual gas composition, which is similar for both.
Coalbed Methane (CBM)
Science And Technology coalbed methane coal seams
Coalbed Methane: Formation, Extraction & India's CBM Resources
CBM is pure methane gas naturally stored in coal seams
India has abundant CBM reserves in Jharia, Raniganj, and other coalfields
CBM extraction reduces mining safety risks by removing explosive methane
What is CBM
Coalbed Methane (CBM) is pure methane gas that gets trapped in coal seams during coal formation over millions of years. Unlike conventional natural gas found in rock reservoirs, CBM is adsorbed (stuck to the surface) of coal particles.
CBM vs Conventional Gas
Aspect | Coalbed Methane | Conventional Natural Gas |
|---|---|---|
Location | Coal seams | Porous rock reservoirs |
Gas composition | Pure methane (95%+) | Methane + ethane + propane |
Storage method | Adsorbed on coal surface | Free gas in rock pores |
Extraction depth | 300-1000 meters | 1000-4000+ meters |
CBM in India
Jharia coalfield (Jharkhand) - largest CBM potential in India
Raniganj coalfield (West Bengal) - first commercial CBM production
Sohagpur coalfield (Madhya Pradesh) - significant reserves
Coal India Limited and private companies actively extract CBM
Trap: CBM is pure methane, not a mixture like shale gas
Trap: India has abundant CBM sources - don't confuse with shale gas availability
Trap: CBM comes from coal seams, not sedimentary rock like shale gas
Shale Gas Extraction
Science And Technology shale gas fine-grained sedimentary rocks
Shale Gas: Formation, Composition & Extraction Technology
Shale gas is mainly methane trapped in shale rock, not propane-butane mixture
Extracted using hydraulic fracturing (fracking) and horizontal drilling
USA became world's largest gas producer due to shale gas revolution
Formation & Composition
Shale gas is natural gas trapped in fine-grained sedimentary rock formations called shales. The gas is mainly methane (70-90%) along with smaller amounts of ethane, propane, and butane - NOT just propane and butane as the wrong statement claims.
Shale Gas Composition
Component | Percentage | Use |
|---|---|---|
Methane | 70-90% | Primary fuel component |
Ethane | 5-15% | Petrochemical feedstock |
Propane | 2-8% | LPG, heating fuel |
Butane | 1-5% | LPG, gasoline blending |
Shale Gas Extraction Process
%%{init: {"flowchart": {"wrappingWidth": 460}}}%%
flowchart TD
s1["`**Horizontal Drilling**
Drill vertically then horizontally into shale layer`"]
s2["`**Hydraulic Fracturing**
Pump water, sand, chemicals to create fractures`"]
s3["`**Gas Flow**
Gas flows through fractures to wellbore`"]
s4["`**Surface Collection**
Gas captured and processed at surface`"]
s1 --> s2
s2 --> s3
s3 --> s4Major trap: Shale gas is mainly methane, not propane-butane mixture
Trap: Shale gas needs fracking technology - different from conventional drilling
Trap: Shale refers to the rock type, not the gas composition
India's Shale Gas Resources
Science And Technology
India's Shale Gas Basins: Identified Resources & Exploration Status
India HAS identified shale gas sources in multiple basins
Cambay Basin (Gujarat) - major shale gas potential
Commercial extraction still under development due to technical challenges
India's Shale Gas Reality
Contrary to Statement 2 in the question, India HAS identified significant shale gas resources in several sedimentary basins. The Directorate General of Hydrocarbons has mapped these resources, though commercial extraction is still developing.
Major Shale Gas Basins in India
Basin | Location | Estimated Resources | Status |
|---|---|---|---|
Cambay Basin | Gujarat | High potential | Exploration ongoing |
Krishna-Godavari Basin | Andhra Pradesh | Significant reserves | Assessment phase |
Cauvery Basin | Tamil Nadu | Moderate potential | Initial studies |
Damodar Valley | West Bengal, Jharkhand | Identified resources | Early exploration |
Shale Gas Basins Location
Source: Rapid Uplift — Rapid Uplift: India Basin-Wise Shale Gas Estimates · suvratk.blogspot.com
Exploration Challenges
Water scarcity - fracking requires large water volumes
Environmental concerns - groundwater contamination risks
Technology gaps - need advanced horizontal drilling expertise
High costs - extraction more expensive than conventional gas
Critical trap: Statement says 'no shale gas sources found' - this is FALSE
Trap: India has both CBM and shale gas resources, not just CBM
Trap: Don't confuse identified resources with commercial production
Unconventional Natural Gas Types
Science And Technology
Unconventional vs Conventional Natural Gas: Key Differences & Types
Unconventional gas requires special extraction techniques unlike conventional gas
CBM, shale gas, tight gas are three main unconventional types
Conventional gas flows easily from porous rock reservoirs
Classification Basis
Natural gas is classified as conventional or unconventional based on reservoir characteristics and extraction difficulty. Conventional gas flows easily from porous rocks, while unconventional gas needs special techniques to extract.
Conventional vs Unconventional Gas
Aspect | Conventional Gas | Unconventional Gas |
|---|---|---|
Rock type | Porous sandstone/limestone | Tight shale/coal seams |
Extraction method | Vertical drilling | Horizontal drilling + fracking |
Flow rate | High natural flow | Low flow, needs stimulation |
Cost | Lower extraction cost | Higher extraction cost |
Examples | Traditional gas fields | CBM, shale gas, tight gas |
Types of Natural Gas
# Natural Gas Resources
## Conventional Gas
- Sandstone reservoirs
- Limestone reservoirs
- Easy extraction
## Unconventional Gas
- Coalbed Methane (CBM)
- Shale Gas
- Tight Gas
- Gas HydratesTrap: Both CBM and shale gas are unconventional - don't mix up their characteristics
Trap: Extraction method differs more than gas composition between types
Trap: India has all unconventional types - CBM commercially viable, shale gas under development