© NERC All rights reserved Is shale gas a global game- changer? Mike Stephenson.

© NERC All rights reserved

Is shale gas a global game-

changer?

Mike Stephenson


What’s all the fuss about?

© NERC All rights reserved Source: Nature Sept 2011


Source: Nature Sept 2011




Shale basics


1 mm


Where does the organic material come from?

Land plant material and seawater algae collect in mud

Older, deeper shale layer


500 m

0 m

• Biological decay – biogenic methane

• Organic matter ‘cooked’ – thermogenic methane

Old deep shale layer

Burial over millions of years


Conventional and unconventional


Conventional and unconventional


Sand grain

Sand graingas

gas

0.25mm

shalesandstone


Adsorbed gas and gas in pores

Phytoclast

Pyrite


Shale layer

sandstone

Cap rockConventional: Trap

Unconventional:Continuous

accumulation


Fracking basics

• Cracks the shale

• High pressure water or nitrogen, 350-700 bar (350 to 700 atmospheres)


Where is the shale?


Britain


Polish shale gas


Siekierki power station in Warsaw


Russia and gas


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


If Poland switched from coal fired power stations to gas fired power stations it would cut

its CO2 emissions by 41-49%



Shale gas and the environment




Clash of cultures


Groundwater

contamination


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 ‰


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


Contamination from fracking?Osborn et al. 2011, PNAS

• Studied:• Methane in

shallow water wells in shale gas areas

• measured methane content and

δ13C


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


Water wells

Unlikely to have casing failure on so many new

wells

Shale well Shale well


Not peer reviewedDec 2011

Molofsky et al. 2011


Molofsky et al. 2011

© NERC All rights reserved Molofsky et al. 2011


Hydraulic connectivity between the shale gas formations and the overlying shallow drinking water aquifers?

Hydraulic connectivity?Warner et al. 2012


Types of groundwater


Role of science


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


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


http://www.bgs.ac.uk/research/energy/shalegas/

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