© nerc all rights reserved is shale gas a global game- changer? mike stephenson
TRANSCRIPT
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Where does the organic material come from?
Land plant material and seawater algae collect in mud
Older, deeper shale layer
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500 m
0 m
• Biological decay – biogenic methane
• Organic matter ‘cooked’ – thermogenic methane
Old deep shale layer
Burial over millions of years
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Shale layer
sandstone
Cap rockConventional: Trap
Unconventional:Continuous
accumulation
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Fracking basics
• Cracks the shale
• High pressure water or nitrogen, 350-700 bar (350 to 700 atmospheres)
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Poland’s choices?
• Renewables –little potential?• Nuclear, long lead in (10 yrs), expensive• Keep burning coal and pay the ?high carbon price• Build gas plants (1-2 yrs), pay ETS, rely on imported gas?• CCS on coal fired power stations• Polish shale gas in gas fired power stations
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If Poland switched from coal fired power stations to gas fired power stations it would cut
its CO2 emissions by 41-49%
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Woody materialδ13C ~ -23.5 ‰ (Stephenson
et al. 2008, 2010)
plankton and algaeδ13C ~ -28.0 ‰
Basics: Environments, organic matter and δ13C
Typical lower Carb organic matter δ13C ~ -25.0 ‰
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Basics: Methane – biogenic and thermogenic
• Biogenic/bacterial (e.g. wetland, landfill) – high C1/C2+ ratio, low δ13C values
• Thermogenic (e.g. natural gas, coalbed methane) – low C1/C2+ ratio, higher (less negative) δ13C values
-80
-70
-60
-50
-40
-30
1 10 100 1000 10000
CH4/(C2H6 + C3H8)
δ13C
-CH
4 ‰
THERMOGENIC
BIOGENIC /BACTERIAL
-80
-70
-60
-50
-40
-30
1 10 100 1000 10000
CH4/(C2H6 + C3H8)
δ13C
-CH
4 ‰
THERMOGENIC
BIOGENIC /BACTERIAL
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Contamination from fracking?Osborn et al. 2011, PNAS
• Studied:• Methane in
shallow water wells in shale gas areas
• measured methane content and
δ13C
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What did they find?
• Higher methane concentrations in water wells close to shale gas wells
• δ13C suggests thermogenic
• Authors then say ‘likely to be shale gas from the fracking’
• No evidence of contamination with fracking fluids
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Water wells
Unlikely to have casing failure on so many new
wells
Shale well Shale well
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Hydraulic connectivity between the shale gas formations and the overlying shallow drinking water aquifers?
Hydraulic connectivity?Warner et al. 2012
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Concerns about shale gas
Things we don't have to worry about
Things we need to regulate carefully for public safety
and public opinion
Independent science: assess risk
Low risk High risk
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Conclusions
• Shale gas could be a game changer
• Britain might have substantial potential for shale gas
• No peer-reviewed evidence of methane contamination from fracking
• Earthquakes are a natural result of fracking but should be manageable
• Peer-reviewed independent science has a special role in building regulator, investor and public confidence