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Coal Bed Methane (CBM) in India

Tribhuban Chandra Patra

1. Introduction

Coal Bed Methane (CBM) is an environment friendly clean fuel withproperties similar to that found in natural gas. Most of the CBM gas is in anadsorbed state on the micropores of the coal surface. Thus, coal is boththe source and reservoir rock for CBM. The generated CBM is stored in thecoal as a monomolecular layer, adsorbed on the internal surfaces of the

coal matrix except for the small amount of free gas that is occasionallyfound in the cleat system of the coal. CBM exploitation is done by simpledepressurization. Accordingly the method of exploiting CBM involvesdrilling wells in the coal seam and subjecting the coal seam to hydro

fracturing. The well is then dewatered. Once the pressure is reducedsufficiently, the flow of gas begins.

2. CBM in Indian Context

India is endowed with rich deposits of coal and lignite which could host vastquantities of CBM. The coal seams are confined to two stratigraphichorizons: The Gondwana coal of Permian age and in Tertiary sequences.

These coal and lignite seams contain varying amount of CBM gasdepending on the rank of the coal, depth of burial and geo-tectonic

settings of the basins. The largest growth in demand for natural gas in theworld exists in India. Large resources of high rank coal in the countryprovide ample opportunities for harnessing this source of non-conventional

energy. Resource potential of about 1000 Billion Cubic Meters (BCM) ofCBM gas from coal deposits in India offer for international bidding is just abeginning of development of yet another source of energy.

3. ONGCs Efforts

ONGC started CBM Exploration activities in India in 1992 throughassessment of Indian Coal basins based upon the available data. Thepreliminary assessment revealed that the Gondwana coals (Permian Age)of Damodar Valley coal basins are prospective candidates for CBM

Exploration. To pursue the CBM venture further, ONGC initiated CBMexploration activities by drilling 2 R&D wells in Durgapur area ofRaniganj coalfield in 1995-96. As per the study of the ONGC Task Force,based on available coal mining data and gas content data, Jharia coalfieldwas ranked to be the most prospective. Accordingly one R&D well was

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drilled in its Parbatpur Sector in 1997 which flowed CBM gas for the firsttime in the country. So far ONGC has drilled 7 boreholes in Raniganj Block

and has gathered significant CBM specific information of the Block.Exploratory activities are underway in this area.

As per this classification, Indian coal basins were subdivided into fourcategories in which Jharia, Bokaro, Raniganj and North KaranpuraBasins were grouped under Category-1, being most prospective.

Apart from Parbatpur, activities have also been undertaken by ONGC in itsadjoining areas, where 6 Core holes/Boreholes have already been drilled byONGC for acquiring CBM specific information to increase acreage of

Exploration. Meanwhile, ONGC and Coal India Ltd. had jointly identified anarea of 21.5 sq km adjacent to ONGCs activity area for joint working.

ONGC-CIL jointly submitted PEL application for a total area 84.55 Sqkm. In consideration of the above, Govt. of India awarded the Block to

ONGC-CIL Consortium again on nomination basis in 2002.

The assessment of Barakar coal seams in Parbatpur Sector through 4

exploratory wells has indicated very good CBM potential. In fact, stable gasproduction from a single test well (5 coal seams) of 6500 m3/d over oneyear period has been obtained with an initial maximum gas flow of24000m3/dand cumulative gas flow of 9 MMm3 has been obtained in2.5 years which is 12% of the estimated recoverable reserve. As a followup to the above encouraging results in a small area of around 1.5 Sq Km,where the four wells are located, ONGC has planned to drill 9 Pilot wellscovering the entire 18 Sq Km area of Parbatpur to establish the production

potential.

To augment CBM exploration activities in the country GOI offered sevenCBM blocks on bidding under CBM Policy-I and nine blocks under thesecond round of bidding. Out of the seven bid blocks in first round ofbidding, ONGC-IOC Consortium was awarded two Blocks viz. Bokaro andNorth Karanpura. Also ONGC-CIL Consortium was awarded Jharia andRaniganj CBM Blocks on nomination basis due to a lot of exploratoryefforts already put by ONGC in these two fields. Out of the 9 Blocks inSecond round of bidding, ONGC has bagged 4 Blocks; South Karanpura,

North Karanpura (West), Satpura, Wardha independently and 1 Block;Barmer-Sanchor with Consortium partner GSPCL.

So, a total of 9 CBM Blocks are available to ONGC as on date and ofthese nine, 6 are in Eastern part of India falling in the coalfields of Damodar

Valley Basins in the states of West Bengal and Jharkhand.

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4. CBM Blocks with ONGC

Jharia Block (84.5 sq. km.) Jharkhand(Participative Interest, ONGC: CIL 90:10)

8 boreholes outside Parbatpur Block and 2 Exploratory wells outsideParbatpur Sector to be drilled I Exploration Phase

9 pilot wells in Parbatpur Sector to be drilled in Pilot Phase All the locations of 9 pilot wells released. Locations of 8 boreholes and 2 exploratory wells under approval.

Raniganj Block (240 Sq Km)(Participative Interest, ONGC: CIL 74:26)

1 exploratory well and 8 boreholes are to be drilled in Exploration Phase Data analysis and studies in progress for locations, as stated above.

Bokaro Block (95 sq. km.), Jharkhand(Participative Interest, ONGC: IOC 80:20)

8 Boreholes and 2 exploratory wells are to drilled and completed inExploration Phase

At present Drilling of borehole in progress. Drilling has been completed for 5Boreholes.

Locations released for 2 exploratory well locations.

North Karanpura Block (340 sq. km.)Jharkhand(Participative Interest, ONGC: IOC 80:20)

9 Boreholes and 2 exploratory wells are to drilled and completed inExploration phase.

At present Drilling of borehole in progress. Drilling has been completed for 5Boreholes.

Locations released for 2 exploratory well locations.

North Karanpura (west) Block (267 sq. km.) Jharkhand(ONGC 100%)

2 exploratory wells and 8 boreholes are to be drilled in Exploration Phase

Work to start after getting PEL. PEL awaited.

South Karanpura Block (70 sq. km.) Jharkhand(ONGC 100%)

3 exploratory wells and 10 Boreholes are to be drilled in exploration Phase Work to start after getting PEL. PEL is awaited.