Global Methane Forum Washington DC 28-30 March 2016
Gas from sealed areas – a hazard or resource?
by Dr D P Creedy
Sindicatum Sustainable Resources
Vice-chair UNECE Group of Experts on CMM
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Global mine gas resource
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9%
51%
2%
38%CMM
VAM
Mined coal
SAM/AMM
Mine gas in the life cycle of coal mining
Mining cycle Gas exploitation Gas composition
Exploration CBM from surface wells
Mainly CH4
Development Pre drained CMMCH4 + air
Production Post drained CMM
Sealing SAM CH4 + air + N2 + CO2
Mine closure AMM CH4 + N2 + CO2
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Basic concepts – gas release from longwall mining
Goaf Face
Coal
Coal
Coal
Coal
Coal
Coal
Flor seams40m to 70m
Roof seams160m to 200m
The w orkedse am
Limit o f gas release zone
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What is Sealed Area Methane (SAM)?
5From Lunarzewski
What is Sealed Area Methane (SAM)?
6From Lunarzewski and Creedy, 2006
Methane Emission - During and Post Production (Mine A-1, LW 9)
0
200
400
600
800
1000
1200
1400
-14 -8 -2 5 11 17 23 29 35 41 47 53 59 65 71 77 83
Time (months)
Meth
an
e e
mis
sio
n (
litr
es/s
ec)
During production Post productionMethane flows during coal production
SAM flows
Panel sealed
SAM resources and reserves
• SAM resource = residual volume of gas available in un-mined coal and void spaces
• SAM reserves = gas recoverable at commercial flow rates at a suction pressure that can be applied without inducing significant increase in CO and O2 concentrations. Flooded areas are excluded.
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Why seal off mined-out areas?
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Atmospheric pressure rising
9
Airway Sealed areaSeal
Leakage flow
Atmospheric pressure falling
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Airway Sealed areaSeal
Leakage flow
Seal control
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Gas drainage
Gas sampling
Water drainage
Nitrogen injection
Packing injection
Control of sealed areas creates best conditions
for methane recovery
• Good standard of sealing – high quality gas
• Gas and water monitoring – good data for planning
• Underground gas drainage or surface venting arrangements – gas production facility
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Feasibility of SAM extraction and use
SAM resources & reserves
• Residual gas content of coal seams• Quantity of unworked coal comprising the
gas reservoir• Dimensions of the sealed area• Water inflows • Gas quality
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Feasibility of SAM extraction and use
Gas extraction
• Access to sealed areas –underground, surface borehole, shaft
• Methane drainage capacity
• Expertise and skills in gas extraction and use
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Feasibility of SAM extraction and use
Commercial and legal factors
• Gas and power price• Accessibility of market – pipeline,
customer, grid connection• Carbon revenues• Ownership of the gas and land access
rights
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Revenue from SAM
Where are the opportunities?
Extensive sealed areas in working, gassy, longwall mines represent potential mine gas production opportunities.
Where mining depths are relatively shallow SAM can be accessed easily from surface boreholes drilled into abandoned mine roadways.
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Conclusions
Sealed Area Methane (SAM) is similar in origin to Abandoned Mine Methane (AMM).
The difference is in the accessibility and controllability of the gas for SAM compared with AMM.
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Conclusions
SAM is a potential asset that can provide :
–Additional value from mining using proven technology
–Clean energy
–Carbon revenues from emissions mitigation
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Conclusions
Attention to SAM production detail will reduce sealed area explosion risk and vice versa
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For further information please email:
Thank you for listening
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