Environmental Risks Associated with Shale Gas University de...

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Environmental Risks Associated with Shale
GasUniversity de...
Professor Zoe Shipton, Dept. of Civil
Environmental Engineering, University of
Strathclyde
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Royal Society/Royal Academy of Engineering
working group report

• Terms of reference
• What are the major risks associated with
  hydraulic fracturing as a means to extract shale
  gas in the UK?
• Can these risks be effectively managed? If so,
  how?

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Headline messages

• Yes the risks can be managed, as long as
  operational best practices are implemented and
  enforced through regulation.
• Cross-cutting issues
• Monitoring
• Sharing data
• Attention must be paid to the way in which risks
  scale up

4
Protestors concerns
http//econews.com.au/news-to-sustain-our-world/br
itain-plans-major-tax-breaks-for-shale-gas/

• Seismicity and fracture propagation
• Water abstraction and use
• Wastewater and well integrity
• Fugitive emissions

5
Protestors concerns
http//econews.com.au/news-to-sustain-our-world/br
itain-plans-major-tax-breaks-for-shale-gas/

• Seismicity and fracture propagation
• Water abstraction and use
• Wastewater and well integrity
• Fugitive emissions

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Seismicity is inherent to hydraulic fracturing
Microseismic monitoring of a typical hydraulic
fracturing operation in the Barnett Shale, Texas,
USA (Zoback et al 2010).
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UK Natural seismicity (red) and Coal
mining-induced seismicity (green) from 1382 to
2012
Magnitude UK frequency
-1.0 100 kg person jumps down 2 m
0.0 Not detected by BGS  
1.0 100s each year  
2.0 25 each year Felt by very few in very quiet conditions
3.0 3 each year Felt by people at rest similar to passing of a truck
4.0 1 every 3-4 years Felt by many people some dishes broken.
5. 0 1 every 20 years Felt by all people fallen plaster some chimneys broken.
Source British Geological Survey
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Fracture growth vs depth of overlying water
sources (Fisher and Warpinski 2012)
Data from Marcellus Shale, USA
Channel tunnel 75 m (250 ft)
Burj Khalifa, Dubai 828 m (2717 ft)
Ben Nevis 1334 m (4409 ft)
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Mitigating induced seismicity

• National surveys (BGS or others)
• Site-specific surveys (operators)
• In-situ stress measurements
• Microseismic monitoring
• Traffic light monitoring systems
• before, during and after
• feed back to allow mitigation

• Where are potential faults?
• How close are they to slipping?
• Can we watch to see how things change as we
  inject?

Operators should share data with DECC and BGS to
establish a national database
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Geological uncertainty and risk

• vchdth

US basins largely undeformed UK basins
significantly folded and faulted Preece Hall
earthquakes
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Mitigating induced seismicity

• July 2013 DECC now requires a Hydraulic
  Fracturing Programme (HFP) detailed risk
  assessment - control and mitigation measures for
  fracture containment and potential induced
  seismicity
• Detailed geological modelling to delineate any
  faults
• Characterise local stress fields,
• Monitor for small seismic events
• UK OOG Guidelines for UK Well Operators on
  Onshore Shale Gas Wells emphasise that Operators
  should not overlook the potential presence of
  faults that cannot be detected given the limits
  of seismic reflection surveys.
• https//www.gov.uk/government/publications/about-s
  hale-gas-and-hydraulic-fracturing-fracking/ 
• www.ukoog.org.uk/elements/pdfs/ShaleGasWellGuideli
  nes.pdf

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Protestors concerns
http//econews.com.au/news-to-sustain-our-world/br
itain-plans-major-tax-breaks-for-shale-gas/

• Seismicity and fracture propagation
• Water abstraction and use
• Wastewater and well integrity
• Fugitive emissions

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Water consumption

• Water needed to operate a hydraulically fractured
  shale well for a decade
• 5 M US gallons (19,000 cubic metres) The amount
  needed to water a golf course for a month
• The amount needed to run a 1000 MW coal-fired
  power plant for 12 hours
• The amount lost to leaks in United Utilities
  region in northwest England every hour
• Moore (2012), Gas works? Shale gas and its policy
  implications, Policy Exchange London.
  http//www.policyexchange.org.uk/images/publicatio
  ns/gas20works20-20feb2012.pdf

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Integrated water management

• Minimise water use and reduce abstracting
  pressures
• Recycle and reuse wastewater where possible
• Construction, regulation and siting of any future
  onshore disposal wells need further investigation

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Protestors concerns
http//econews.com.au/news-to-sustain-our-world/br
itain-plans-major-tax-breaks-for-shale-gas/

• Seismicity and fracture propagation
• Water abstraction and use
• Wastewater and well integrity
• Fugitive emissions

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Are fracking fluids toxic?
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Permeability

• Even fracked mudstones have very low
  permeabilities by hydrogeological standards
  (typically lt 1 mD)
• They are typically several orders of magnitude
  lower than those of freshwater aquifers
  (typically gt 1000 mD)
• Surrounding, un-fracked mudstones are less
  permeable still (e.g. 10-1 10-3 mD)
• It is hard to get concerned about permeability

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Head gradient

• production zones of shale gas typically lie at
  great depths, and they are purposely
  de-pressurised by pumping, if anything the head
  gradient will be downwards from shallow aquifers
  towards the shale gas zones, not upwards to the
  aquifers
• Vast experience of mining beneath the seabed and
  aquifers shows that anything more than about 100m
  of low-permeability strata will be enough to rule
  out downward or upward flow

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Maximum extent of hydraulic fractures
From Davies et al (2012) Hydraulic fractures
how far can they go? Marine and Petroleum
Geology (2012). http//www.dur.ac.uk/resources/dei
/JMPG_1575.pdf