Challenges & Opportunities of Coalbed Methane

7/23/2019 Challenges & Opportunities of Coalbed Methane

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Challenges & Opportunities of

Coalbed Methane

By,

Md Athher Qadri,

M. Tech ( G E),

R030307005



Key Contents

Introduction

Important Properties

The driving Force

Potential

Challenges

Opportunities

Conclusion



Introduction

Coalbed methane: CBM is a form of Natural Gas adsorbed into the solidmatrix of the coal.

Presence of CBM in underground mining is a potential safety risk

The methane is in a near-liquid state, lining the inside of pores within thecoal (called the matrix).

An unconventional reservoir : Cleats formed during Coalification process.

Coal stores 6 to 7 times more gas than the equivalent rock volume of aconventional gas reservoir.

The open fractures in the coal (called the cleats) can also contain free gas orcan be saturated with water.



Properties

Permeability- is low, usually due to cleats-face cleats provide path forhigher permeability than butt cleats

Porosity –usually very small ranging from 0.1 to 10 %

Adsorption capacity-

Defined as the volume of gas adsorbed per unit mass of coal usuallyexpressed in SCF (standard cubic feet , the volume at standard pressureand temperature conditions) gas/ton of coal.

The capacity to adsorb depends on the rank and quality of coal.

usually between 100 to 800 SCF/ton

Other affecting parameters are coal density, initial gas phase concentration,critical gas saturation, irreducible water saturation, relative permeability towater and gas at conditions of S

w

= 1.0 and Sg

= 1



Driving Force

To meet future demand and to offset production decline ofconventional reserves.

Coal-bed methane (CBM) is a clean burning fuel for domestic

and industrial uses, and its extraction reduces explosion hazards

in underground coal mines.

India is endowed with huge reserves of bituminous coal of

Paleozoic and Tertiary ages within the CBM window at depths of

nearly 250-1200 meters.

Lack of data on producible reserves of CBM, gas content,

reservoir saturation and permeability has prevented full

exploitation of the resource.



Driving Force

India wants foreign and domestic private companies for the

exploration and commercial exploitation of CBM resources at some

of the underground coal mines.

Contracts that will be awarded will be similar to the "concession"concept in oil and gas exploration. Coal-bearing areas will be leased

to the successful bidders and they will have to explore and test-drill.

If recovery and commercial exploitation of the CBM gas in these

areas ultimately prove viable, the exploring firms will be free to

construct pipelines and sell the gas to consumers or they may set upgas-based power plants.



Potential

India is among the top ten countries in coal resources, having an estimated coal

reserve of 160 million metric tons, with an estimated methane resource of 850BCM.

The Indian coal is mainly confined to the Permian Gondwana basins and thetertiaries. Tertiary coals are generally found to be lignitic to sub-bituminous in rank

and are generally considered to be unsuitable for coalbed methane target.

Tertiary coals are widespread in Assam, Meghalaya, Arunachal Pradesh, Tamil Nadu,Rajasthan and Gujarat.

Methane emission studies from working mines of India reported most of thedegree three gassy mines (> 10 cubic m/ton), are confined in the four DamodarValley coal fields, viz. Raniganj, Jharia, Bokaro and North Karanpura in Bihar andWest Bengal. In these areas, the thickest bituminous coals are extensivelydeveloped in the Barakar measurers and in Raniganj measures of Lower and UpperPermian age, respectively.



Challenges

Evaluation of coal properties

Construction of adsorption isotherm

Study of geological basins

Technological needs

Environmental Impact



Technological Needs

For assessment of properties of the reservoir

Remote sensing imagerySeismic survey

Drilling

Technological needs during production

The primary concerns for drilling are overpressure of gas/water kicks,high permeability which leads to loss of circulation fluid, formationdamage due to the nature of coal and hole sloughing.

The rigs commonly used are portable, self-propelled and hydraulically-driven, having a top head drive or a Kelly drive. A major problem duringdrilling could be the excessive water flow. Drilling with pressure may behindered due to escape of large quantities of water through the coal

seams.



HOW IS COALBED METHANE

DEVELOPED?

Methane locked in coal beds is usually not as expensive to

develop as natural gas found in other geologic formationsbecause modified water well drilling rigs can be used in place of

specialized oil and gas drilling rigs.

Cased wells tend to deter, though not always prevent, gas from

seeping into nearby rock beds and underground water

formations called aquifers

Fractures that run through coal beds are usually filled withwater. The deeper the coal bed, the less water is present, but

the more saline (or salty) it becomes. Water pressure holds

methane in the coal bed.



To release the gas, its partial pressure must be reduced by removing water

from the coal beds.

Once the pressure is lowered, the gas and water move through the coal bed

and up the wells.

At first, coalbed methane wells produce mostly water, but over time, theamount of water declines and gas production rises as the bed is dewatered.

Water removal may continue for several years. The water is usually

discharged on the surface or injected into aquifers.


DEVELOPED?



Drill rigs are brought to well sites by trucks,

and access roads must be constructed.

Electric or gas powered motors are used to

power the pumps and compressor stations.

Pipelines are also built to gather the gas

from each well and transport it to customersin distant markets.


DEVELOPED?



WHAT ARE THE PROBLEMS WITH COALBED METHANEDEVELOPMENT?

Disposal of water removed from coalbed methane wells

Drinking water levels drop

Contamination of aquifers

Venting and seeping of methane and other chemicals

Underground fires

Air pollution

Destruction of land and harm to wildlife

Impacts on landowners

Environmental & health hazard problems



Opportunities

CBM potential of INDIA is estimated to be 850 BCM

India is endowed with huge reserves of bituminous coal of

Paleozoic and Tertiary ages within the CBM window at

depths of nearly 250-1200 meters.

The yearn for Clean Development mechanism



Proposed Method of Gas Capture

ONGC intend to develop the Parbatpur test area further into a small scalepilot study

Use of inseam directional drilling to overcome the low permeability of thecoal.

The borehole will be cased for its full depth before cutting a window in thecasing at the various seam horizons allowing directional drilling, inseam,for up to 1000m depending on geology and continuity of the seam.



Each directionally drilled hole will have a

number of boreholes off it containing in seam.

Upon completion of the drilling an electrical

submersible pump will be installed in the baseof the borehole and de-watering undertaken.

However, short-radius drilling technology is

not yet readily available so ONGC will be

advised to examine Medium Radius Drilling(MRD), an established Australian technology

also used in China.




Directional drilling is not available in-house to ONGC and it isunderstood that expressions of interest have been sought

from third parties. There will be a significant amount of

drilling required to drill one well with associated in seam

drilling and the cost is likely to be substantial.

Within the study area it is proposed to construct seven

drilling pads from which up to three wells could be drilled. It

is anticipated that the total number of wells will be in theorder of 21.




Conclusion

Coalbed methane exploration may open up a new energyindustry in India.

Evaluation of coal properties, construction of adsorptionisotherm, and study of geological setting of coal basinsshould be an integral part of initial research efforts.

It is desirable to work out the techno-economic viabilityof a project after R&D efforts are completed and beforeexploration and exploitation are taken up.



Thank You

Challenges & Opportunities of Coalbed Methane

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