Shale gas extraction in the UK: a review of hydraulic fracturing

Shale gas
extraction
in the UK:
a review of
hydraulic
fracturing
June 2012

Shale gas extraction in the UK: a review of hydraulic fracturing
Issued: June 2012 DES2597

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2 Shale gas extraction in the UK: a review of hydraulic fracturing

Contents
Summary ........................................................4 Chapter 6 – Risk management ....................48
6.1 The UK’s goal based approach to
Recommendations ..........................................6 regulation ......................................................48
6.2 Collecting data to improve risk
Terms of reference .........................................8 assessments ................................................. 49
6.3 Environmental risk assessments ................... 51
Chapter 1 – Introduction.................................9
1.1 Hydraulic fracturing.........................................9 Chapter 7 – Regulating shale gas .................53
1.2 Stages of shale gas extraction ...................... 10 7.1 Conditions of Petroleum Exploration and
1.3 The global policy context .............................. 10 Development Licences..................................53
1.4 Environmental concerns in the USA ............. 11 7.2 Conditions of local planning permission.......54
1.5 Environmental concerns in Europe ............... 14 7.3 Notification of well construction and the
1.6 Moratoria ...................................................... 15 well examination scheme..............................54
1.7 Concerns about seismicity ............................ 15 7.4 Conditions of environmental permits............55
1.8 The UK policy context ................................... 17 7.5 Regulating production activities on a
nationwide scale ...........................................55
Chapter 2 – Surface operations .................... 19
2.1 Fracturing fluid .............................................. 19 Chapter 8 – Research on shale gas ..............57
2.2 Water requirements .....................................20 8.1 Uncertainties affecting small scale
2.3 Managing wastewaters .................................20 exploratory activities .....................................57
2.4 Disposal of wastewaters ...............................21 8.2 Uncertainties affecting large scale
2.5 Disposal of solid wastes ...............................22 production activities ......................................57
2.6 Managing methane and other emissions ....22 8.3 Funding research on shale gas .....................58

Chapter 3 – Well integrity ............................24
3.1 Preventing well failure ...................................25 References ....................................................60
3.2 Improving the well examination scheme .....26
3.3 Detecting well failure ....................................27 Acronyms .....................................................66

Chapter 4 – Fracture propagation ................. 31 Glossary ........................................................68
4.1 Monitoring fractures .....................................31
4.2 Constraining fracture growth ........................32 Appendix 1 – Working Group .......................70
4.3 Hydraulic fracturing below aquifers ..............34
Appendix 2 – Evidence gathering .................72
Chapter 5 – Induced seismicity ....................40
5.1 Natural seismicity ..........................................40 Appendix 3 – Review Panel ..........................75
5.2 Seismicity induced by coal mining ...............40
5.3 Seismicity induced by hydraulic fracturing... 41
5.4 Factors affecting seismicity induced by
hydraulic fracturing .......................................42
5.5 Mitigating induced seismicity .......................43
5.6 Damage to well integrity ...............................45
5.7 Seismicity induced by disposal.....................45
5.8 Regulating induced seismicity ......................46

Shale gas extraction in the UK: a review of hydraulic fracturing 3

SUMMARY

Summary
The health, safety and environmental risks associated Concerns have also been raised about seismicity
with hydraulic fracturing (often termed ‘fracking’) induced by hydraulic fracturing. Natural seismicity
as a means to extract shale gas can be managed in the UK is low by world standards. On average,
effectively in the UK as long as operational best the UK experiences seismicity of magnitude 5 ML
practices are implemented and enforced through (felt by everyone nearby) every twenty years, and
regulation. Hydraulic fracturing is an established of magnitude 4 ML (felt by many people) every
technology that has been used in the oil and gas three to four years. The UK has lived with seismicity
industries for many decades. The UK has 60 years’ induced by coal mining activities or the settlement of
experience of regulating onshore and offshore oil abandoned mines for a long time. British Geological
and gas industries. Survey records indicate that coal mining-related
seismicity is generally of smaller magnitude than
Concerns have been raised about the risk of fractures natural seismicity and no larger than 4 ML. Seismicity
propagating from shale formations to reach overlying induced by hydraulic fracturing is likely to be of even
aquifers. The available evidence indicates that this smaller magnitude. There is an emerging consensus
risk is very low provided that shale gas extraction that the magnitude of seismicity induced by hydraulic
takes place at depths of many hundreds of metres or fracturing would be no greater than 3 ML (felt by
several kilometres. Geological mechanisms constrain few people and resulting in negligible, if any, surface
the distances that fractures may propagate vertically. impacts). Recent seismicity induced by hydraulic
Even if communication with overlying aquifers were fracturing in the UK was of magnitude 2.3 ML and
possible, suitable pressure conditions would still be 1.5 ML (unlikely to be felt by anyone). The risk of
PGEGUUCT[ HQT EQPVCOKPCPVU VQ ƃQY VJTQWIJ HTCEVWTGU seismicity induced by hydraulic fracturing can be
More likely causes of possible environmental TGFWEGF D[ VTCHƂE NKIJV OQPKVQTKPI U[UVGOU VJCV WUG
contamination include faulty wells, and leaks and real-time seismic monitoring so that operators can
spills associated with surface operations. Neither respond promptly.
cause is unique to shale gas. Both are common to
all oil and gas wells and extractive activities. Monitoring should be carried out before, during and
after shale gas operations to inform risk assessments.
Ensuring well integrity must remain the highest Methane and other contaminants in groundwater
priority to prevent contamination. The probability of should be monitored, as well as potential leakages of
well failure is low for a single well if it is designed, methane and other gases into the atmosphere. The
constructed and abandoned according to best geology of sites should be characterised and faults
practice. The UK’s well examination scheme was KFGPVKƂGF /QPKVQTKPI FCVC UJQWNF DG UWDOKVVGF VQ
set up so that the design of offshore wells could be the UK’s regulators to manage potential hazards,
reviewed by independent, specialist experts. This inform local planning processes and address wider
UEJGOG OWUV DG OCFG ƂV HQT RWTRQUG HQT QPUJQTG concerns. Monitoring of any potential leaks of
activities. Effects of unforeseen leaks or spills methane would provide data to assess the carbon
can be mitigated by proper site construction and footprint of shale gas extraction.
impermeable lining. Disclosure of the constituents
QH HTCEVWTKPI ƃWKF KU CNTGCF[ OCPFCVQT[ KP VJG 7-
Ensuring, where possible, that chemical additives
are non-hazardous would help to mitigate the
impact of any leak or spill.


SUMMARY

The UK’s goal based approach to regulation is to more concentrated during waste treatment.
be commended, requiring operators to identify and NORM management is not unique to shale gas
assess risks in a way that fosters innovation and GZVTCEVKQP 014/ KU RTGUGPV KP YCUVG ƃWKFU HTQO
continuous improvement in risk management. The the conventional oil and gas industries, as well
UK’s health and safety regulators and environmental as in mining industries, such as coal and potash.
regulators should work together to develop Much work has been carried out globally on
IWKFGNKPGU URGEKƂE VQ UJCNG ICU GZVTCEVKQP VQ JGNR monitoring levels of radioactivity and handling
operators carry out goal based risk assessments NORMs in these industries.
according to the principle of reducing risks to As
Low As Reasonably Practicable (ALARP). Risk Shale gas extraction in the UK is presently at a very
assessments should be submitted to the regulators small scale, involving only exploratory activities.
for scrutiny and then enforced through monitoring Uncertainties can be addressed through robust
activities and inspections. It is mandatory for OQPKVQTKPI U[UVGOU CPF TGUGCTEJ CEVKXKVKGU KFGPVKƂGF
operators to report well failures, as well as other in this report. There is greater uncertainty about
accidents and incidents to the UK’s regulators. the scale of production activities should a future
Mechanisms should be put in place so that reports shale gas industry develop nationwide. Attention
can also be shared between operators to improve must be paid to the way in which risks scale up.
risk assessments and promote best practices across Co-ordination of the numerous bodies with
the industry. regulatory responsibilities for shale gas extraction
must be maintained. Regulatory capacity may
An Environmental Risk Assessment (ERA) should need to be increased.
be mandatory for all shale gas operations. Risks
should be assessed across the entire lifecycle of Decisions are soon to be made about shale gas
shale gas extraction, including risks associated with extraction continuing in the UK. The next round of
the disposal of wastes and abandonment of wells. issuing Petroleum Exploration and Development
Seismic risks should also feature as part of the ERA. Licences is also pending. This report has not
attempted to determine whether shale gas extraction
Water requirements can be managed through should go ahead. This remains the responsibility
integrated operational practices, such as recycling of the Government. This report has analysed the
and reusing wastewaters where possible. Options technical aspects of the environmental, health and
for disposing of wastes should be planned from safety risks associated with shale gas extraction to
the outset. Should any onshore disposal wells be inform decision making. Neither risks associated with
necessary in the UK, their construction, regulation the subsequent use of shale gas nor climate risks
and siting would need further consideration. JCXG DGGP CPCN[UGF GEKUKQP OCMKPI YQWNF DGPGƂV
from research into the climate risks associated with
Wastewaters may contain Naturally Occurring both the extraction and use of shale gas. Further
Radioactive Material (NORM) that are present in DGPGƂV YQWNF CNUQ DG FGTKXGF HTQO TGUGCTEJ KPVQ VJG
UJCNGU CV NGXGNU UKIPKƂECPVN[ NQYGT VJCP UCHG NKOKVU public acceptability of all these risks in the context
of exposure. These wastewaters are in need of of the UK’s energy, climate and economic policies.
careful management should NORM become


SUMMARY

Recommendations
Recommendation 1 Recommendation 3
To detect groundwater contamination: To mitigate induced seismicity:

r The UK’s environmental regulators should work r BGS or other appropriate bodies should carry
with the British Geological Survey (BGS) to carry out national surveys to characterise stresses and
out comprehensive national baseline surveys of identify faults in UK shales. Operators should carry
methane and other contaminants in groundwater. out site-specific surveys to characterise and identify
local stresses and faults.
r Operators should carry out site-specific
monitoring of methane and other contaminants r Seismicity should be monitored before, during
in groundwater before, during and after shale gas and after hydraulic fracturing.
operations.
r Traffic light monitoring systems should be
r Arrangements for monitoring abandoned wells implemented and data fed back to well injection
need to be developed. Funding of this monitoring operations so that action can be taken to mitigate
and any remediation work needs further any induced seismicity.
consideration.
r DECC should consider how induced seismicity is
r The data collected by operators should be to be regulated. Operators should share data with
submitted to the appropriate regulator. DECC and BGS to establish a national database of
shale stress and fault properties so that suitable
Recommendation 2 well locations can be identified.
To ensure well integrity:
Recommendation 4
r Guidelines should be clarified to ensure the To detect potential leakages of gas:
independence of the well examiner from the
operator. r Operators should monitor potential leakages of
methane or other emissions to the atmosphere
r Well designs should be reviewed by the before, during and after shale gas operations.
well examiner from both a health and safety
perspective and an environmental perspective. r The data collected by operators should be
submitted to the appropriate regulator. These
r The well examiner should carry out onsite data could inform wider assessments, such as
inspections as appropriate to ensure that wells the carbon footprint of shale gas extraction.
are constructed according to the agreed design.
Recommendation 5
r Operators should ensure that well integrity tests Water should be managed in an integrated way:
are carried out as appropriate, such as pressure r Techniques and operational practices should be
tests and cement bond logs. implemented to minimise water use and avoid
abstracting water from supplies that may be
r The results of well tests and the reports of
under stress.
well examinations should be submitted to
the Department of Energy and Climate r Wastewater should be recycled and reused
Change (DECC). where possible.

r Options for treating and disposing of wastes
should be planned from the outset. The
construction, regulation and siting of any future
onshore disposal wells need further investigation.


SUMMARY

Recommendation 6 Recommendation 9
To manage environmental risks: Co-ordination of the numerous bodies with regulatory
responsibilities for shale gas extraction should be
r An Environmental Risk Assessment (ERA) should maintained. A single body should take the lead.
be mandatory for all shale gas operations, Consideration should be given to:
involving the participation of local communities
at the earliest possible opportunity. r Clarity on roles and responsibilities.

r The ERA should assess risks across the entire r Mechanisms to support integrated ways of
lifecycle of shale gas extraction, including the working.
disposal of wastes and well abandonment.
Seismic risks should also feature as part of r More formal mechanisms to share information.
the ERA.
r Joined-up engagement of local communities.
Recommendation 7
Best practice for risk management should be r Mechanisms to learn from operational and
implemented: regulatory best practice internationally.

r Operators should carry out goal based risk Recommendation 10
assessments according to the principle of The Research Councils, especially the Natural
reducing risks to As Low As Reasonably Environment Research Council, the Engineering
Practicable (ALARP). The UK’s health and safety and Physical Sciences Research Council and the
regulators and environmental regulators should Economic and Social Research Council, should
work together to develop guidelines specific to consider including shale gas extraction in their
shale gas extraction to help operators do so. research programmes, and possibly a cross-Research
Council programme. Priorities should include
r Operators should ensure mechanisms are put in research into the public acceptability of the extraction
place to audit their risk management processes. and use of shale gas in the context of UK policies on
climate change, energy and the wider economy.
r Risk assessments should be submitted to the
regulators for scrutiny and then enforced through
monitoring activities and inspections.

r Mechanisms should be put in place to allow
the reporting of well failures, as well as other
accidents and incidents, between operators.
The information collected should then be shared
to improve risk assessments and promote best
practices across the industry.

Recommendation 8
The UK’s regulators should determine their
requirements to regulate a shale gas industry should
it develop nationwide in the future. Skills gaps and
relevant training should be identified. Additional
resources may be necessary.


SUMMARY

Terms of reference
6JG 7- )QXGTPOGPVoU %JKGH 5EKGPVKƂE #FXKUGT 5KT Methodology
John Beddington FRS, asked the Royal Society and A Working Group was set up to oversee this project
the Royal Academy of Engineering to carry out an (see Appendix 1). The Working Group met on six
KPFGRGPFGPV TGXKGY QH VJG UEKGPVKƂE CPF GPIKPGGTKPI occasions when it was briefed by other experts.
evidence relating to the technical aspects of the Consultations with other experts and stakeholders
risks associated with hydraulic fracturing to inform were held between meetings. Submissions were
government policymaking about shale gas extraction received from a number of individuals and learned
in the UK. societies (see Appendix 2). This report has been
reviewed by an expert Review Panel (see Appendix 3)
The terms of reference of this review were: and approved by the Engineering Policy Committee
of the Royal Academy of Engineering and the Council
r What are the major risks associated with hydraulic of the Royal Society.
fracturing as a means to extract shale gas in the
UK, including geological risks, such as seismicity, The Royal Academy of Engineering and The Royal
and environmental risks, such as groundwater 5QEKGV[ CTG ITCVGHWN VQ VJG )QXGTPOGPV 1HƂEG HQT
contamination? 5EKGPEG HQT KVU ƂPCPEKCN UWRRQTV HQT VJKU TGXKGY

r Can these risks be effectively managed?
If so, how?

This report has analysed environmental and health
and safety risks. Climate risks have not been
analysed. The risks addressed in this report are
restricted to those associated with the onshore
extraction of shale gas. The subsequent use of shale
gas has not been addressed.


CHAPTER 1

Introduction
1.1 Hydraulic fracturing pumped into the well to maintain the pressure in the
Shale is a common type of sedimentary rock formed well so that fracture development can continue and
from deposits of mud, silt, clay and organic matter. proppant can be carried deeper into the formation
Shale gas mainly consists of methane, although (API 2009). A well may be too long to maintain
other gases may also be present, trapped in shale sufficient pressure to stimulate fractures across its
with very low permeability. Shale gas does not entire length. Plugs may be inserted to divide the well
readily flow into a well (‘produce’). Additional into smaller sections (‘stages’). Stages are fractured
stimulation by hydraulic fracturing (often termed sequentially, beginning with the stage furthest away
‘fracking’) is required to increase permeability (see and moving towards the start of the well. After
Figure 1). Once a well has been drilled and cased fracturing, the plugs are drilled through and the well
(‘completed’), explosive charges fired by an electric is depressurised. This creates a pressure gradient
current perforate holes along selected intervals so that gas flows out of the shale into the well.
of the well within the shale formation from which Fracturing fluid flows back to the surface (‘flowback
shale gas is produced (‘production zone’). Pumps water’) but it now also contains saline water
are used to inject fracturing fluids, consisting of with dissolved minerals from the shale formation
water, sand (‘proppant’) and chemicals, under (’formation water’). Fracturing fluid and formation
high pressure into the well. The injection pressure water returns to the surface over the lifetime of the
generates stresses in the shale that exceed its well as it continues to produce shale gas (‘produced
strength, opening up existing fractures or creating water’). Although definitions vary, flowback
new ones. The fractures extend a few hundred water and produced water collectively constitute
metres into the rock and the newly created fractures ‘wastewaters’ (EPA 2011).
are propped open by the sand. Additional fluids are


CHAP TER 1

Figure 1 An illustration of hydraulic fracturing (Al Granberg/ProPublica) Fracturing fluids are
injected under pressure to stimulate fractures in the shale. The fractures are propped open by sand
contained in the fracturing fluid so that shale gas can flow out of the shale into the well.

Well

Sand keeps
fractures open

Shale gas Fracture
ﬂows from
fractures into well Mixture of
Well water, sand
and chemical
additives

Fractures

Shale

1.2 Stages of shale gas extraction through them and access only a small volume of
Shale gas extraction consists of three stages: the shale. Horizontal wells are likely to be drilled
and fractured. Once a shale formation is reached
r Exploration. A small number of vertical wells by vertical drilling, the drill bit can be deviated to
(perhaps only two or three) are drilled and run horizontally or at any angle.
fractured to determine if shale gas is present
and can be extracted. This exploration stage may r Abandonment. Like any other well, a shale gas
include an appraisal phase where more wells well is abandoned once it reaches the end of
(perhaps 10 to 15) are drilled and fractured to its producing life when extraction is no longer
characterise the shale; examine how fractures will economic. Sections of the well are filled with
tend to propagate; and establish if the shale could cement to prevent gas flowing into water-bearing
produce gas economically. Further wells may be zones or up to the surface. A cap is welded into
drilled (perhaps reaching a total of 30) to ascertain place and then buried.
the long-term economic viability of the shale.
1.3 The global policy context
r Production. The production stage involves the
commercial production of shale gas. Shales 1.3.1 Potential global shale gas resources
with commercial reserves of gas will typically ‘Gas in place’ refers to the entire volume of gas
be greater than a hundred metres thick and contained in a rock formation regardless of the
will persist laterally over hundreds of square ability to produce it. ‘Technically recoverable
kilometres. These shales will normally have resources’ refers to the volume of gas considered
shallow dips, meaning they are almost horizontal. to be recoverable with available technology. ‘Proved
Vertical drilling would tend to pass straight reserves’ refers to that volume of technically


CHAPTER 1

recoverable resources demonstrated to be estimates the total volume of technically recoverable
economically and legally producible under existing shale gas worldwide to be 6,622 tcf. The USA has
economic and operating conditions. approximately 862 tcf, and China 1,275 tcf (see
Figure 2). In Europe, Poland and France are two of
Shale gas could increase global natural gas the most promising shale gas countries with 187
resources by approximately 40%. The US Energy tcf and 180 tcf of technically recoverable resources,
Information Administration (EIA) estimates the global respectively. Norway, Ukraine and Sweden may also
technically recoverable resources of natural gas possess large technically recoverable resources.
(largely excluding shale gas) to be approximately The EIA estimates the UK’s technically recoverable
16,000 trillion cubic feet (tcf) (EIA 2011). The EIA resources to be 20 tcf (EIA 2011)

Figure 2 Estimates of technically recoverable shale gas resources (trillion cubic feet,
tcf) based on 48 major shale formations in 32 countries (EIA 2011) Russia, Central Asia,
Middle East, South East Asia and central Africa were not addressed in the Energy Information
Administration report from which this data was taken.

83 Norway
388 Canada
UK 20 187 Poland
France 180
862 USA
1275 China
Algeria 231 Pakistan 51
290 Libya
681 Mexico India 63

226 Brazil

62 Paraguay Australia 396
64 Chile 485 South Africa

774 Argentina

1.3.2 Global climate change and energy security molecule of methane is greater than that of carbon
Shale gas is championed by some commentators as dioxide, but its lifetime in the atmosphere is shorter.
a ‘transition fuel’ in the move towards a low carbon On a 20-year timescale, the global warming potential
economy, helping to displace higher-emitting fuels, of methane is 72 times greater than that of carbon
such as coal (Brinded 2011). Others argue that shale dioxide. On a century timescale, it is 25 times greater
gas could supplement rather than displace coal use, (IPCC 2007).
further locking in countries to a fossil fuel economy
(Broderick et al 2011). The development of shale gas 1.4 Environmental concerns in the USA
could also reduce and/or delay the incentive to invest Hydraulic fracturing was pioneered in the 1930s and
in zero- and low-carbon technologies and renewable ƂTUV WUGF CHVGT VJG 5GEQPF 9QTNF 9CT KP VJG 75# VQ
energy (Broderick et al 2011, Stevens 2010). exploit the relatively shallow Devonian Shale in the
GCUVGTP 75 CPF #PVTKO 5JCNG KP VJG /KFYGUV 6JG ƂTUV
There are concerns that even small leakages of well to be hydraulically fractured was in 1949. Only
methane during shale gas extraction may offset the a modest volume of gas was recovered. Advances
effects of lower carbon dioxide emissions (Howarth in technology in the late 1980s and early 1990s led
et al 2011). The global warming potential of a to directional drilling and hydraulic fracturing in the


CHAP TER 1

Barnett Shale in Texas (Selley 2012). An important 1.4.1 Improper operational practices
turning point came in the 1990s. Geochemical There has been widespread concern in the USA
studies of the Antrim Shale of the Michigan Basin about the environmental impact of hydraulic
revealed that the gas being released was not fracturing. One cause for concern has been improper
thermogenic (produced by the alteration of organic operational practices. A US Environmental Protection
matter under high temperatures and pressures over Agency (EPA) study reported that hydraulic fracturing
long time periods) but was biogenic (produced had contaminated groundwater and drinking
by bacteria) (Martini et al 1998). This discovery water supplies in Pavillion, Wyoming (DiGiulio et
opened up new areas for exploration where the al 2011). The well casing was poorly constructed,
shale had previously been deemed either immature and the shale formations that were fractured were
or over-mature for thermogenic gas generation. as shallow as 372m. Many claims of contaminated
At the same time, progress was being made in water wells due to shale gas extraction have been
methods of drilling, such as directional drilling that made. None has shown evidence of chemicals
could steer the drill bit to exploit regions with high HQWPF KP J[FTCWNKE HTCEVWTKPI ƃWKFU 9CVGT YGNNU KP
concentrations of carbon and where the shale is areas of shale gas extraction have historically shown
most amenable to being fractured. By 2002-03, the high levels of naturally occurring methane before
combination of hydraulic fracturing and directional operations began. Methane detected in water wells
drilling made shale gas commercially viable. with the onset of drilling may also be mobilised by
vibrations and pressure pulses associated with the
Shale gas production has been enhanced by US lease drilling (Groat and Grimshaw 2012). In 2011, the EPA
regulations that require a leaseholder to commence was directed by Congress to undertake a study to
operations within a primary term period (normally better understand the potential impacts of hydraulic
ƂXG [GCTU QT NQUG VJG NGCUG TGICTFNGUU QH RTKEG 5JCNG fracturing on drinking water resources. This EPA
gas production in the USA has caused gas prices to study is examining impacts from the acquisition of
fall as supply has outstripped demand. Shale gas has water and its mixing with chemicals to create fracture
FKXGTUKƂGF FQOGUVKE GPGTI[ UWRRNKGU CPF TGFWEGF ƃWKF VJTQWIJ VQ VJG OCPCIGOGPV QH ƃQYDCEM CPF
75 FGRGPFGPEG QP KORQTVU QH NKSWGƂGF PCVWTCN ICU RTQFWEGF YCVGT KPENWFKPI FKURQUCN # ƂTUV TGRQTV
Shale gas rose from 2% of US gas production in KU GZRGEVGF CV VJG GPF QH 6JG ƂPCN TGUWNVU
2000 to 14% in 2009, and is projected to rise to are due in 2014. In 2011, the Secretary of Energy
more than 30% by 2020 (EIA 2011). Advisory Board Natural Gas Subcommittee submitted
its recommendations to improve the safety and
environmental performance of shale gas extraction
(see Textbox 1).


CHAPTER 1

Textbox 1 Recommendations of the US Secretary of Energy Advisory Board Natural Gas
Subcommittee (DoE 2011a, DoE 2011b)

Recommendations ready for implementation Recommendations ready for implementation
primarily by federal agencies primarily by state agencies
r Communication among federal and state r Measurements of groundwater should be
regulators should be improved. Federal funds made prior to any shale gas operations to
should be provided to support the non- provide a baseline to assess any claims of
profit State Review of Oil and Natural Gas water contamination.
Environmental Regulations (STRONGER) and
Ground Water Protection Council (GWPC). r Microseismic monitoring should be carried
STRONGER began as a voluntary programme out to assure that fracture growth is
developed to improve state regulations and constrained to producing formations.
has since emerged as a partnership between
industry, non-profit groups and regulators that r Best practice for well construction should
develops best practice, including through new be developed and implemented, including
guidelines. pressure testing and cement bond logs, to
verify rock formations have been properly
r Incentives should be provided for states to isolated.
offer their regulation framework to peer review
under STRONGER. Extra funding would r Inspections should be carried out to confirm
allow GWPC to expand its Risk Based Data that operators have remediated any defective
Management System that helps states collect well cementation effectively. Inspections
and publicly share data, such as environmental should also be carried out at safety-critical
monitoring of shale gas operations. stages of well construction and hydraulic
fracturing.
r Operators should disclose all chemicals
used in fracturing fluid and not just those r The composition of water should be
that appear on Material Safety Data Sheets. monitored and publicly reported at each
Disclosure should be reported on a well-by- stage of shale gas extraction, including the
well basis and made publicly available. Extra transport of water and waste fluids to, and
funding would support GWPC’s fracturing fluid from, well sites.
chemical disclosure registry, Frac Focus, so
that information can be accessed, according to
chemical, well, company and geography. Recommendations whose implementation
require new partnerships
r Operators and regulators should be r A systems approach to water management
encouraged to reduce air emissions using should be adopted, requiring more effective
proven technologies and practices. Systems sharing of federal and state responsibilities.
should be implemented to monitor air
emissions from shale gas operations, the r Mechanisms should be established to engage
results of which should be made publicly regulators, operators and local communities
available. The data collected should be used to discuss measures to minimise operational
to assess the carbon footprint of shale gas impacts, including scientific studies to assess
extraction compared to other fuels. impacts on local water resources, land use,
wildlife and ecology.


CHAP TER 1

1.4.2 Exemptions from regulation and Awareness of Chemicals Act (FRAC ACT) bills
Another cause for concern was a number of were introduced in the House of Representatives
exemptions granted to shale gas extraction from and Senate. The FRAC ACT would have required
federal regulations. The 2005 Energy Act exempted companies to disclose such details, although not the
hydraulic fracturing from being considered an proprietary formula. These bills had been proposed
‘underground injection’ under the Safe Drinking in the previous session of Congress but never
Water Act. Compliance with various federal became law.
requirements to prevent water contamination
was not necessary. Fracturing wastes are exempt Environmental protection remains mainly a state
from disposal restrictions under the Resource responsibility. In some states, requirements
Conservation and Recovery Act. Operators are exempted from federal regulation are still imposed
exempt from certain liabilities and reporting through state regulation. Some states are revising
requirements relating to waste disposal under their regulations with a particular focus on three
the Comprehensive Environmental Responsibility, areas of concern: water abstraction and disclosure
Compensation, and Liability Act. Exemption from QH HTCEVWTKPI ƃWKF EQORQUKVKQP YGNN EQPUVTWEVKQP
the Emergency Planning and Community Right to and wastewater management (Groat and Grimshaw
Know Act means the type and quantity of chemicals 2012). Some states may have more capacity and
to be used in fracturing do not need to be disclosed experience to regulate shale gas operations than
to the EPA. In 2010, the Fracturing Responsibility other states (see Textbox 2).

Textbox 2 Complications of US state and federal regulation

A study by the University of Texas at Austin r Well construction. Some states are updating
reviewed state regulations and enforcement provisions for well construction, according
capabilities in 16 US states where shale gas to site-specific operational and geological
extraction is currently underway, or is anticipated conditions.
(Groat and Grimshaw 2012). This study
concluded that variation exists among states in r Wastewater management. Some states are
the regulation of: requiring operators to formulate disposal plans.
In some states, disposal is primarily by
r Water abstraction and disclosure of underground injection. In others with less
fracturing fluid composition. In some states, suitable subsurface conditions disposal is via
groundwater is privately owned and subject discharge into publicly owned treatment works.
to different requirements than in other states The latter method has been prohibited by some
where groundwater is owned by the state and states. Other states require pre-treatment before
subject to state abstraction permits. More discharge. In some shale gas areas, wastes from
uniform disclosure of the composition multiple well sites are managed at a centralised
of fracturing fluids may be needed among disposal site.
state regulators.

1.5 Environmental concerns in Europe potential to extract and use unconventional fossil
Shale gas extraction in Europe is at the exploration fuel resources, including shale gas, should be
stage. It is many years away from US levels of assessed (European Council 2011). In 2012, the
commercial production, especially in the light European Commission (EC) judged that its existing
of differences in geology, public acceptability, legal framework was adequate to address shale gas
population density, tax breaks and environmental extraction (Vopel 2012). Shale gas could reduce some
regulation (Stevens 2010). In 2011, European European countries’ dependence on natural gas
Union (EU) Heads of State concluded that Europe’s imports (European Parliament 2012b).


CHAPTER 1

The EC Directorate-General for the Environment 1.7 Concerns about seismicity
is conducting a desk study on environmental and Concerns in the UK have focused on seismicity
health risks associated with hydraulic fracturing induced by hydraulic fracturing. ‘Seismicity’ or
to identify knowledge gaps. The EC Directorate- ‘seismic events’ refer to sudden phenomena that
General for Climate Action is carrying out a similar release energy in the form of vibrations that travel
study focused on gas emissions associated with through the Earth as sound (seismic) waves. Energy
shale gas extraction, including potential leakages of may be released when rocks break and slide past
methane. The EC Directorate-General for Energy has each other on surfaces or cracks (‘faults’). Energy
carried out a project on licensing, authorising and may also be released when rocks break in tension,
the issuing of operational permits for shale gas. The opening up cracks or fractures. The passage and
Joint Research Centre (JRC) is examining whether TGƃGEVKQP QH UGKUOKE YCXGU ECP DG OQPKVQTGF D[
the exposure scenarios of Chemical Safety Reports seismometers at seismic stations. Geophones are
under Registration, Evaluation, Authorisation and used along regular lines (‘seismic lines’) or grids
Restriction of Chemicals regulation are adequate VQ QDVCKP VYQ QT VJTGG FKOGPUKQPCN RTQƂNGU QH VJG
for shale gas extraction. The JRC is also assessing 'CTVJoU UWDUWTHCEG UVTWEVWTG
nUGKUOKE TGƃGEVKQP
the potential impacts on water and land use under surveys’). Seismicity is measured according to
various national and EU-wide scenarios. Results of the amount of energy released (magnitude) or the
these studies should be available by the end of 2012. effect that energy release has at the Earth’s surface
(intensity) (see Textbox 3).
All EU member states are members of an Ad
Hoc Technical Working Group on Environmental On 1st April 2011, the Blackpool area in north
Aspects of Unconventional Fossil Fuels, In Particular England experienced seismicity of magnitude
Shale Gas. The Working Group seeks to exchange 2.3 ML shortly after Cuadrilla Resources (‘Cuadrilla’,
information; identify best practice; assess the hereafter) hydraulically fractured a well at its Preese
adequacy of regulation and legislation; and provide Hall site. Seismicity of magnitude 1.5 ML occurred
ENCTKV[ VQ QRGTCVQTU +V OGV HQT VJG ƂTUV VKOG KP on 27th May 2011 following renewed fracturing of
January 2012 and was attended by representatives the same well. Hydraulic fracturing was suspended.
of approximately two thirds of member states. The Cuadrilla commissioned a set of reports to investigate
Working Group may meet again in summer 2012 the cause of seismicity (de Pater and Baisch 2011).
when the results of some of the aforementioned The Department of Energy and Climate Change
EC research are published. It is unclear whether the (DECC) also commissioned an independent
Working Group will continue to meet thereafter. report that was published for public comment
(Green et al 2012).
1.6 Moratoria
Environmental concerns have led to moratoria on
hydraulic fracturing for shale gas extraction in parts
of the USA and in other countries. In May 2010, the
Marcellus Shale Bill was passed in Pennsylvania,
enforcing a three-year moratorium while a
comprehensive environmental impact assessment
is carried out. In August 2010, New York State
imposed a temporary moratorium, pending further
research into environmental impacts. Moratoria
have also been imposed elsewhere, including in the
province of Quebec, Canada (March 2011), France
(July 2011), South Africa (August 2011) and Bulgaria
(January 2012).


CHAP TER 1

Textbox 3 Measuring seismic magnitude and intensity

Magnitude scales are calibrated to Richter’s The frequency of the radiated seismic waves is
magnitude scale. The scale is logarithmic so the proportional to the size of the fracture. Since
smallest events can have negative magnitudes. engineered hydraulic fractures are typically small,
Each unit step in the scale indicates a 32-fold seismic events induced by hydraulic fracturing
increase in the energy released. Seismic intensity only produce high frequency radiated seismic
is an indication of how much a seismic event waves, and so do not produce ground shaking
affects structures, people and landscapes at the that will damage buildings. The number of people
Earth’s surface. Surface effects are compared who feel small seismic events is dependent on the
to a scale originally developed by Mercalli background noise.
that considers who can feel an event along
with visual and structural effects. The Mercalli The British Geological Survey (BGS) runs a network
scale has been superseded by the European of approximately 100 stations to monitor seismicity
Macroseismic Scale that incorporates new in the UK. The Atomic Weapons Establishment
knowledge about how buildings behave during also has a limited number of stations to monitor
seismic events. international compliance with the Comprehensive
Nuclear Test Ban Treaty. Other seismic stations
The effect a given seismic event will have at include those maintained for research by
the earth’s surface depends on several factors. universities. The detection limit of this national
The deeper a seismic event occurs the more its network is a function of background noise that
radiated energy is attenuated. A deeper seismic OC[ KPENWFG VTCHƂE VTCKPU CPF QVJGT KPFWUVTKCN
event will have a lower intensity than a shallower noise, as well as natural noise, such as wind. Given
event of the same magnitude. Different average background noise conditions in mainland
materials attenuate seismic waves to different UK, a realistic detection limit of BGS’ network is
degrees. Soft rocks, such as shale, attenuate magnitude 1.5 ML. For regions with
seismic waves more than hard rocks, such more background noise, the detection limit may
as granite. Different buildings and structures be closer to magnitude 2-2.5 ML. Vibrations from
respond differently depending on how they are a seismic event of magnitude 2.5 ML are broadly
constructed. The response of a building to a GSWKXCNGPV VQ VJG IGPGTCN VTCHƂE KPFWUVTKCN CPF
seismic event also depends on the frequency other noise experienced daily (see Table 1).
of the ground shaking. High frequencies
(above 20-30 Hz) will do relatively little damage.


CHAPTER 1

Table 1 The average annual frequency of seismic events in the UK

Magnitude (ML) Frequency in the UK Felt effects at the surface
-3.0 Not detected by BGS’ network Not felt
0.0 Not detected by BGS’ network Not felt
1.0 100s each year Not felt, except by a very few under especially
favourable conditions.
2.0 25 each year Not felt, except by a very few under especially
favourable conditions.
3.0 3 each year (GNV D[ HGY RGQRNG CV TGUV QT KP VJG WRRGT ƃQQTU QH
buildings; similar to the passing of a truck.
4.0 1 every 3-4 years Felt by many people, often up to tens of kilometres
away; some dishes broken; pendulum clocks may
stop.
5. 0 1 every 20 years Felt by all people nearby; damage negligible in
buildings of good design and construction; few
instances of fallen plaster; some chimneys broken.

1.8 The UK policy context 6JG ƂTUV 7- YGNN VQ GPEQWPVGT UJCNG ICU YCU FTKNNGF
The UK has experience of hydraulic fracturing and KP +VU UKIPKƂECPEG CV VJG VKOG YGPV WPPQVKEGF
directional drilling for non-shale gas applications. as abundant conventional reservoirs made shale
Over the last 30 years, more than 2,000 wells have gas extraction uneconomic. It was not until the
been drilled onshore in the UK, approximately 200 mid-1980s that research began into the potential
(10%) of which have been hydraulically fractured for gas production from UK shales. In 2003, the
to enhance recovery. The combination of hydraulic Petroleum Revenue Act was repealed, exempting
fracturing and directional drilling allowed the shale gas production from the Petroleum Revenue
FGXGNQROGPV QH 9[VEJ (CTO ƂGNF KP QTUGV KP Tax (Selley 2012). In 2008, 97 Petroleum Exploration
1979. Discovered by British Gas in the 1970s and and Development Licences were awarded for shale
QRGTCVGF D[ $TKVKUJ 2GVTQNGWO UKPEG VJG ƂGNF gas exploration in the UK during the 13th Round of
is responsible for the majority of UK onshore oil Onshore Licensing (see chapter 7). A 14th licensing
RTQFWEVKQP CPF KU 'WTQRGoU NCTIGUV QPUJQTG QKN ƂGNF round is pending.
Over 200 wells have been drilled. Drilling vertically
onshore then horizontally out to sea has proved Industry interest in shale gas extraction in the
more cost-effective than building offshore platforms, UK includes:
allowing oil to be produced beneath the Sandbanks
estate, Bournemouth, from oil reservoirs 10km away. r England. Five potential shale gas exploration
In 1996, British Gas hydraulically fractured a well well sites have been identified by Cuadrilla in
KP VJG 'NUYKEM )CU ƂGNF KP .CPECUJKTG
MO HTQO Lancashire. The first test well was drilled in August
Cuadrilla’s Preese Hall well). Gas has been produced 2010 at Preese Hall; a second at Grange Hill Farm
from it ever since. In the 1990s, several wells were later that year; and a third near the village of
also fractured in the UK to extract coal bed methane. Banks in August 2011. Hydraulic fracturing has


CHAP TER 1

been undertaken at only one site. DECC has also 1.8.1 UK climate change and energy security
granted a license for a site in Balcombe, West The UK government has agreed to meet a number of
Sussex identified by Cuadrilla. Three possible sites domestic and European targets to decarbonise the
have been identified in the Mendip Hills by UK UK economy (Moore 2012). The Climate Change Act
Methane and Eden Energy. Planning permission 2008 calls for an 80% reduction in greenhouse gas
has been sought for boreholes for geological emissions by 2050. This includes an interim target
samples. UK Methane has stated it has no interest of a 34% reduction in emissions by 2020 and a 50%
in hydraulic fracturing at this stage. One site has reduction in emissions by the 2023–2027 budget
been identified in Woodnesborough, Kent, by (all from a baseline of 1990). The EU has a target to
Coastal Oil and Gas Ltd. Planning permission reduce EU-wide greenhouse gas emissions by 20%
has been granted. Neither Cuadrilla’s West between 1990 and 2020. It has also agreed that 20%
Sussex nor Coastal Oil and Gas Ltd’s Kent sites of total energy production across the EU should be
have yet been granted permission for drilling or generated by renewable sources, and so the UK
hydraulic fracturing. has committed to sourcing 15% of its energy from
renewables.
r Wales. Three sites have been identified by Coastal
Oil and Gas Ltd. DECC has given permission for The House of Commons Energy and Climate Change
drilling at two of these sites, but not hydraulic Committee carried out an inquiry into shale gas
fracturing. Planning permission has been granted in 2011. The inquiry considered the prospects for
for the sites at Neath and Maesteg where wells shale gas in the UK; risks and hazards involved;
will be deepened to obtain geological samples. potential carbon footprint of large-scale shale gas
Planning permission was refused at Llandow, Vale extraction; and implications for the UK of large-
of Glamorgan. The decision is being appealed with scale shale gas production around the world (HoC
a public inquiry. 6JG %QOOKVVGG EQPENWFGF VJCV KH C UKIPKƂECPV
amount of shale gas enters the UK market (whether
r Scotland. Although potential shale formations from domestic or foreign sources), it will probably
do exist in Scotland, to date there has been discourage investment in more expensive, lower
no interest in shale gas extraction. Consent for carbon emission renewables (HoC 2011).
hydraulic fracturing has been provided to one
operator with an interest in extracting coal bed Over the last decade, the UK has experienced
methane. reduced domestic production from the North Sea
and an increased reliance on natural gas imports.
r Northern Ireland. Tamboran Resources has New pipelines from Norway and the Netherlands
an interest to extract shale gas in an area that CPF NKSWGƂGF PCVWTCN ICU OCMG WR VJG FKHHGTGPEG
extends across the border between Northern The House of Commons Energy and Climate Change
Ireland and the Republic of Ireland. Committee also concluded that domestic resources
could reduce the UK’s dependence on imports, but
The Environment Agency (EA), serving England and the effect on energy security may be ‘unlikely to be
Wales, has been reviewing the adequacy of existing enormous’ (HoC 2011). The UK has an open gas
regulation. In 2011, the Scottish Environmental market with large new import infrastructure and a
Protection Agency (SEPA) published a position diversity of potential gas suppliers (Moore 2012).
statement based on its preliminary views of shale
gas extraction (SEPA 2011). The Northern Ireland 1.8.2 Joint academies review
Environment Agency is working with the Irish 6JG 7- )QXGTPOGPVoU %JKGH 5EKGPVKƂE #FXKUGT 5KT
environmental regulator to develop a regulatory John Beddington FRS, asked the Royal Society and
framework suitable for transboundary activities. the Royal Academy of Engineering to carry out an
KPFGRGPFGPV TGXKGY QH VJG UEKGPVKƂE CPF GPIKPGGTKPI
evidence to inform government policymaking about
shale gas extraction in the UK. The following chapters
analyse environmental and health and safety risks
associated with the onshore extraction of shale gas.


CHAPTER 2

Surface operations
(TCEVWTKPI ƃWKF allowing each stage to address local conditions,
6JG ƃWKFU OQUV EQOOQPN[ WUGF HQT J[FTCWNKE such as shale thickness; presence of natural faults;
fracturing are water-based. The water can be and proximity to other well systems (API 2009).
abstracted from surfacewater bodies, such as rivers Operations require specialised equipment, including
and lakes, or from groundwater bodies, such as ƃWKF UVQTCIG VCPMU RTQRRCPV VTCPURQTV GSWKROGPV
aquifers or public and private water sources. Sand and blending and pumping equipment. These
is added as a proppant to keep fractures open. components are assembled and linked to monitoring
Various chemicals are also added (see Figure 3). U[UVGOU UQ VJCV CFLWUVOGPVU ECP DG OCFG VQ ƃWKF
During multistage fracturing, a series of different XQNWOG CPF EQORQUKVKQP ƃWKF KPLGEVKQP TCVG CPF
XQNWOGU QH HTCEVWTKPI ƃWKFU KU KPLGEVGF YKVJ URGEKƂE pressure.
concentrations of proppant and other additives,

(KIWTG 6[RKECN EQORQUKVKQP QH HTCEVWTKPI ƃWKF D[ XQNWOG
UQWTEG $TKVKUJ )GQNQIKECN 5WTXG[
The 0.17% of chemical additives may include scale inhibitor to prevent the build up of scale on the walls
of the well; acid to help initiate fractures; biocide to kill bacteria that can produce hydrogen sulphide
CPF NGCF VQ EQTTQUKQP HTKEVKQP TGFWEGT VQ TGFWEG HTKEVKQP DGVYGGP VJG YGNN CPF ƃWKF KPLGEVGF KPVQ KV CPF
UWTHCEVCPV VQ TGFWEG VJG XKUEQUKV[ QH VJG HTCEVWTKPI ƃWKF

Additives
0.17%

e
Sand
Water 5.23% d
94.60%
a

c b

a. Scale inhibitor
b. Acid
c. Biocide
d. Friction reducer
e. Surfacant

2.1.1 Disclosing the composition of QH HTCEVWTKPI ƃWKF
QT YCUVGYCVGTU QPUKVG ECP DG
fracturing fluid mitigated using established best practices. In the
In the USA, there are calls for operators to disclose UK, installing impermeable site lining (‘bunding’) is
HWNN[ VJG EQORQUKVKQP QH HTCEVWTKPI ƃWKF CFFKVKXGU
UGG typically a condition of local planning permission.
section 1.4.2). This is already required in the UK. In 6JG KORCEV QH HTCEVWTKPI ƃWKF URKNNU ECP DG HWTVJGT
the UK, the environmental regulator has the power mitigated by using non-hazardous chemicals
under the Water Resources Act 1991 to demand the where possible. In the UK, there is no generic list
FKUENQUWTG QH VJG EQORQUKVKQP QH HTCEVWTKPI ƃWKFU QH CRRTQXGF EJGOKECNU HQT WUG KP HTCEVWTKPI ƃWKF
The environmental regulators use a methodology
2.1.2 Spills of fracturing fluid developed by the Joint Agencies Groundwater
5WTHCEG URKNNU QH HTCEVWTKPI ƃWKF OC[ RQUG C ITGCVGT Directive Advisory Group to assess the hazard
contamination risk than hydraulic fracturing itself potential of any chemical to be used, according to
(Groat and Grimshaw 2012). The impact of any spills VJG URGEKƂE UKVG CPF NQECN J[FTQIGQNQIKECN EQPFKVKQPU


CHAP TER 2

2.2 Water requirements 2.2.2 Alternatives to water
There are concerns that hydraulic fracturing could Another option would be to use waterless fracturing
TGSWKTG XQNWOGU QH YCVGT VJCV YQWNF UKIPKƂECPVN[ ƃWKFU 6JGUG KPENWFG IGNU CPF ECTDQP FKQZKFG CPF
deplete local water resources (Entrekin et al 2011). nitrogen gas foams (King 2010). These techniques are
Reported estimates for the volumes of water required important where shales are susceptible to damage
for shale gas extraction vary according to local from water-based fracturing (King 2010). Gelled liquid
geology, well depth and length and the number of RGVTQNGWO ICU
.2) HTCEVWTKPI ƃWKFU EQWNF DQQUV
hydraulic fracturing stages. In the UK, under the initial production rates and allow near full recovery
Water Resources Act 1991, an operator is required QH VJG HTCEVWTKPI ƃWKFU YKVJKP FC[U QH UVKOWNCVKQP
to seek an abstraction permit from the environmental 6JG WUG QH VJGUG ƃWKFU RCTVKEWNCTN[ RTQRCPGDCUGF
regulator if more than 20m3 of water is to be LPG, could reduce the toxicity of wastewaters since
abstracted per day from surface or groundwater they do not dissolve salts, heavy metals or Naturally
bodies. If water is instead sourced from a mains Occurring Radioactive Material (NORM) in shales to
supply, the water company will need to ensure it can the extent that water does.
still meet the conditions of the abstraction permit that
it will already be operating under. 2.3 Managing wastewaters
Approximately 25% to 75% of the injected fracturing
Overall water use is important. Estimates indicate ƃWKF ƃQYU DCEM VQ VJG UWTHCEG YJGP VJG YGNN KU
that the amount needed to operate a hydraulically FGRTGUUWTKUGF 6JKU ƃWKF KU OKZGF YKVJ OGVJCPG
fractured shale gas well for a decade may be and saline water containing minerals from the shale
equivalent to the amount needed to water a golf HQTOCVKQP 6JG XQNWOG QH ƃQYDCEM YCVGT FGRGPFU
course for a month; the amount needed to run a on the properties of the shale, the fracturing design
/9 EQCNƂTGF RQYGT RNCPV HQT JQWTU CPF CPF VJG V[RG QH HTCEVWTKPI ƃWKF WUGF
-KPI
the amount lost to leaks in United Utilities’ region Produced water will continue to return to the
in north west England every hour (Moore 2012). surface over the well’s lifetime. These wastewaters
The rate of abstraction is also important. Hydraulic typically contain salt, natural organic and inorganic
fracturing is not a continuous process. Water is compounds, chemical additives used in fracturing
required periodically during drilling and then at each ƃWKF CPF 014/
02% 8GT[ NKVVNG KU EWTTGPVN[
fracturing stage. Operators could consult water known about the properties of UK shales to explain
utilities companies to schedule operations to avoid YJCV HTCEVKQP QH HTCEVWTG ƃWKF YKNN TGVWTP CU ƃQYDCEM
periods when water supplies are more likely to be water, as well as the composition of formation
under stress (Moore 2012). waters and produced water.1

2.2.1 Alternative sources of water 2.3.1 Storing wastewaters
Water stress can be avoided by using alternative In the USA, wastewaters have historically been
sources of water. Freshwater was necessary early stored onsite in open pits, such as excavated and
in the development of certain US shales when lined containment ponds (API 2009). The possible
friction reducers, scale inhibitors, and particularly leakage of liners has led to calls to avoid the use of
UWTHCEVCPVU UJQYGF RGTHQTOCPEG FKHƂEWNVKGU YJGP pits in favour of closed loop steel tanks and piping
mixed in saline water (King 2010). Technologies systems (Groat and Grimshaw 2012). Open storage
developed to overcome these problems in offshore ponds are not permitted in the UK. Wastewaters
hydraulic fracturing (where the use of seawater is are instead stored in closed metal tanks before
more prevalent) are now being applied to onshore being treated. Leaks or spills of wastewaters can
operations (Harris and van Batenburg 1999). The be managed in the same way as spills of fracturing
use of saline water from deep aquifers is being ƃWKF
UGG UGEVKQP 6JKU JCCTF KU PQV WPKSWG
considered in some US shales (Yost 2011). to shale gas extraction but common to many
industrial processes.

1 Contribution from Professor Richard Davies, Director of Energy Institute, University of Durham (private correspondence)


CHAPTER 2

2.3.2 Reuse of wastewaters 2.3.4 Transporting wastewaters
Integrated operational practices should be adopted The transport of wastewaters offsite is carried out by
to minimise water use and avoid abstracting water road haulage companies licensed by the UK’s health
from supplies that may be under stress. Recycling and safety regulators with experience of transporting
wastewater where possible would reduce the hazardous substances. The UK’s environmental
volumes of wastewater in need of disposal, although TGIWNCVQTU KUUWG ECTTKGT TGIKUVTCVKQP EGTVKƂECVGU
it could concentrate contaminants and thereby and the Department of Transport and Vehicle and
complicate disposal. Operator Services Agency are responsible for vehicle
licensing and testing.
Wastewaters can be diluted with freshwater and
then reused in subsequent fracturing operations. 2.4 Disposal of wastewaters
Pre-treatment may be necessary. The composition Disposal wells may be necessary if wastewater
of wastewaters changes over the lifetime of a volumes exceed the capabilities of onsite, closed-
well. The most appropriate treatment will depend NQQR UVQTCIG VCPM U[UVGOU +PLGEVKQP QH YCUVG ƃWKFU
on the waters’ degree of salinity (King 2010). The into porous and permeable rock formations has been
environment in which some shales were initially VJG RTKOCT[ FKURQUCN QRVKQP HQT YCUVG ƃWKFU HTQO VJG
deposited was marine (King 2012). Produced US oil and gas industry (DoE 2009). Disposal wells
water in the latter stages of shale gas extraction are often depleted oil and gas wells, but wells can be
is more saline owing to the increased amount of FTKNNGF URGEKƂECNN[ HQT FKURQUCN KH KV KU GEQPQOKE VQ FQ
saline formation water that it contains. Desalination so. The site of disposal wells depends on geological
technologies are being developed to control conditions and regulation. In the USA, some wastes
salinity and support reuse of wastewaters. These are transported to disposal sites by truck or pipeline
technologies concentrate salt and recover water (DoE 2009).
through evaporation, distillation, electric separation
or chemical treatment. The most common treatment 2.4.1 Disposing of fluids
WUGU UGNGEVKXG OGODTCPGU VJCV ƂNVGT QWV UCNV KQPU Wastewaters are considered to be an ‘extractive
when high pressure is applied across them. As waste’, and so are regulated under the Mining Waste
well as producing pure water, these desalination Directive. Operators are required to formulate waste
technologies typically produce a small amount of management plans that identify how wastes are to
brine slurry that may be converted to solid waste in minimised, treated, recovered and disposed of. This
a crystalliser before disposal (ALL Consulting 2005). includes identifying environmental and health impacts
Microorganisms, such as bacteria, can exist even and measures to address them, including control and
in deep shale formations, and so may be present monitoring activities. Disposal would be regulated
in the formation water within wastewaters. These in the UK under the Mining Waste Directive and
microorganisms need to be removed for health Water Framework Directive. An environmental permit
and safety and commercial reasons. Bacterial can would be necessary, as well as pre-treatment, before
produce hydrogen sulphide and acids that corrode discharge into a disposal well. If wastewaters contain
well casings, and so potentially contribute to well 014/ CDQXG URGEKƂGF NKOKVU C HWTVJGT RGTOKV YQWNF
HCKNWTG KUKPHGEVKQP VGEJPKSWGU KPENWFG ƂNVTCVKQP be required. The Radioactive Substances Regulation
techniques, as well as ultraviolet light, chlorine, would also apply. Currently, a disposal well would be
iodine, ozone and acid treatments (ALL Consulting constructed in the UK according to the Borehole Sites
2005). and Operations Regulations 1995 if the disposal well
was in a mining area and to a depth of 30m or greater.
Pre-treatment could take place onsite, although this Offshore disposal would involve extra environmental
is currently expensive. Technologies could build on regulations, such as those under the Convention
VJQUG CNTGCF[ WUGF VQ VTGCV YCUVG ƃWKF HTQO QHHUJQTG for the Protection of the Marine Environment of the
oil and gas extraction. Alternatively, wastewaters North-East Atlantic (the OSPAR Convention).
could be transported to a treatment facility offsite.
Numerous facilities exist in the UK with extensive
experience of treating similar wastes from a range
of industrial sectors.


CHAP TER 2

2.5 Disposal of solid wastes
Shale tends to contain more uranium than other RECOMMENDATION
types of rocks. The radioactive decay of uranium-238 Water should be managed in an
produces radium-226 that decays to radon-222 KPVGITCVGF YC[
gas. Other NORM found in shales includes thorium
and lead-210, concentrations of which vary from r Techniques and operational practices
formation to formation. NORM in shales is usually at should be implemented to minimise
NGXGNU UKIPKƂECPVN[ NQYGT VJCP UCHG NKOKVU QH GZRQUWTG water use and avoid abstracting water
NORM dissolves in formation water, so wastewaters from supplies that may be under stress.
need careful management should NORM become
r Wastewater should be recycled and
more concentrated during treatment (King 2012).
reused where possible.
Dissolved NORM may settle out to form solid
wastes, such as mineral scale on the inside of wells
r Options for treating and disposing of
and pipes or sludge that accumulates in storage
wastes should be planned from the
or treatment tanks. Scale is composed primarily of
outset. The construction, regulation and
insoluble barium, calcium and strontium compounds
siting of any future onshore disposal
that precipitate out of wastewaters due to changes
wells need further investigation.
in temperature and pressure. Radium is chemically
similar to these elements, and so is incorporated
into the scales. Sludge settles out of wastewaters 2.6 Managing methane and other emissions
and consists of oily solids often containing silica 8GPVKPI CPF ƃCTKPI QH OGVJCPG CPF QVJGT GOKUUKQPU
compounds and barium. are controlled through conditions of Petroleum
Exploration and Development Licences. The health
NORM management is not unique to shale gas and safety regulator places similar controls under
GZVTCEVKQP 014/ KU RTGUGPV KP YCUVG ƃWKFU HTQO VJG the Borehole Sites and Operations Regulations 1995
conventional oil and gas industries, as well as and and Offshore Installations and Wells (Design and
mining industries, such as coal and potash. Much Construction) Regulations 1996. Local authorities are
work has been carried out globally on monitoring responsible under the Environmental Protection Act
levels of radioactivity and handling NORMs in the 1990 to inspect sites for odour and noise associated
oil and gas industries. For example, it is standard YKVJ VJG XGPVKPI QT ƃCTKPI QH ICU .QECN CWVJQTKVKGU
practice to sandblast pipes to remove scale or to use also have a statutory duty under the Air Quality
a rotating drill bit. The removed scale is then placed in Standards Regulations 2007 to monitor emissions to
sealed containers for later disposal. Scale can also be ensure they do not breach local air quality standards.
removed by dissolving NORM in an aqueous solvent Methane contained in wastewater can be regulated
before re-injecting the NORM-containing solution into by the environmental regulator placing controls
a disposal well (ALL Consulting 2005). on operators’ waste management plans (see
section 2.4.1).
In the UK, solid NORM wastes fall into one of three
categories: very low concentration (‘out of scope’); low The Industrial Emissions Directive would apply if
concentration; medium or high concentration (requires shale gas is processed before injection into the gas
an EPR permit). An environmental permit is required pipeline or combusted to generate electricity and/
for disposing of NORM wastes that exceed ‘out of or heat onsite. A permit would then be needed,
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solid wastes of low and medium concentrations. Some methane (and other air pollutants). Shale gas in
offshore oil production facilities have permits allowing the UK is expected to be of high quality, so large
some NORM wastes to be discharged directly to sea. scale processing may not be necessary. Operators


CHAPTER 2

should still monitor potential leakages of methane
and other emissions before, during and after shale RECOMMENDATION
gas operations. Monitoring before operations would 6Q FGVGEV RQVGPVKCN NGCMCIGU QH ICU
indicate the effects of methane due to non-shale gas
operations in the area or natural seepage (methane r Operators should monitor potential
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and peat deposits). One option would be to construct to the atmosphere before, during and
semi-permanent monitoring stations around the after shale gas operations.
perimeter of a drilling site. Alternatively, emissions
r The data collected by operators should
could be monitored near to the well. Both options
be submitted to the appropriate
face complications. Gas emissions would be diluted
regulator. These data could inform
in the atmosphere before reaching monitoring
wider assessments, such as the carbon
stations, limiting their detection accuracy. Monitoring
footprint of shale gas extraction.
equipment near to the well could be disturbed due to
surface equipment being changed at different stages
of operations. Monitoring data should be submitted
to the appropriate regulator. Reliable data would be
available to inform assessments of health impacts
on local populations (McKenzie et al 2012). These
data could also inform assessments of the carbon
footprint of shale gas extraction (see section 8.2.2).

‘Green completion technologies’ are used in the USA
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water (DoE 2011b). These technologies separate
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directing the recovered gas into pipelines. Methane
and carbon dioxide emissions are reduced compared
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completion technologies could allow emissions
levels similar to those associated with natural gas
extraction (Broderick et al 2011). The EPA has
issued federal regulations making green completion
technologies mandatory for hydraulic fracturing of all
gas wells in the USA from 2015 onwards. No such
requirements exist in the UK for exploratory activities.
Consideration should be given the possible use of
green completion technologies, especially for any
future production activities in the UK, based on best
available technologies and operational best practices.


CHAP TER 3

Well integrity
‘Well integrity’ refers to preventing shale gas from Well failure may arise from poor well integrity
leaking out of the well by isolating it from other resulting from:
subsurface formations (API 2009). The isolation is
provided according to how the well is constructed. r Blowout. A blowout is any sudden and
A series of holes (‘wellbores’) of decreasing diameter uncontrolled escape of fluids from a well
and increasing depth are drilled and lined with steel to the surface.
casing joined together to form continuous ‘strings’
of casing (see Figure 4): r Annular leak. Poor cementation allows
contaminants to move vertically through the
r Conductor casing. Set into the ground to a well either between casings or between casings
depth of approximately 30 metres, the conductor and rock formations.
casing serves as a foundation for the well and
prevents caving in of surface soils. r Radial leak. Casing failures allow fluid to move
horizontally out of the well and migrate into the
r Surface casing. The next wellbore is drilled and surrounding rock formations.
sealed with a casing that runs past the bottom of
any freshwater bearing zones (including but not
Figure 4 An example of a shale gas
limited to drinking water aquifers) and extends all well design (DoE 2009)
the way back to the surface. Cement is pumped
down the wellbore and up between the casing
and the rock until it reaches the surface. Conductor casing

r Intermediate casing. Another wellbore is drilled
and lined by an intermediate casing to isolate the Aquifer
well from non-freshwater zones that may cause
instability or be abnormally pressurised. The Cement
casing may be sealed with cement typically either Surface casing
up to the base of the surface casing or all the way
to the surface.
Salt water zone
r Production casing. A final wellbore is drilled into
the target rock formation or zone containing shale
gas. Once fractured, the shale gas produces into
Intermediate casing
the well. This wellbore is lined with a production Cement
casing that may be sealed with cement either to
a safe height above the target formation up to the
base of the intermediate casing; or all the way to
the surface, depending on well depths and local
geological conditions.

Cement
Production casing

Production Zone


CHAPTER 3

3.1 Preventing well failure 3.1.2 Preventing casing failures
Once drilled, but before casings are installed and
3.1.1 Preventing blowout cemented, instruments can be run down the wellbore
Blowouts are rare. Blowouts can occur when drilling to detect naturally occurring (gamma) radiation and
encounters an over-pressurised, highly permeable measure the density and porosity of the formation
formation. Some shales can be over-pressurised, (API 2009). The diameter of the wellbore can be
but even then blowout is unlikely because shale measured using callipers so that casings are installed
has very low permeability. A recent blowout from a accurately. Once installed and prior to further drilling,
Chesapeake well in Wyoming, USA, resulted from ECUKPIU CTG RTGUUWTG VGUVGF VQ GPUWTG UWHƂEKGPV
gas that had leaked up from the Niobrara Shale into a mechanical integrity and strength so that they can
shallower, more permeable formation. withstand pressures exerted at different phases of the
well’s life, such as those exerted during the fracturing
Blowouts are a major safety hazard to workers. They process (API 2009). Immediately after drilling out of
OC[ CNUQ TGUWNV KP GUECRGU QH ƃWKF KPVQ PGCTD[ UWTHCEG each casing, a formation pressure test (‘leak off test’)
water. The environmental impacts of blowout depend is carried out.
on (Groat and Grimshaw 2012):
3.1.3 Preventing poor cementation
r timing relative to well activities (determining Cementation provides structural support, as well
whether pressurised fracturing fluid or shale as isolation of different rock formations. Cements
gas is released); may be tested in advance to ensure their properties
meet the requirements of particular well designs (API
r whether escape is through the surface casing 2009). Cement needs to completely surround casings
or deeper in the well; to provide a continuous annular seal between casings
and the rock formation, as well as between casings.
r the nature of the risk receptor (whether A cement bond log (CBL) is an acoustic device run
freshwater aquifer or water well). inside casings to detect the presence of cement
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A blowout preventer (BOP) is placed at the top of a
sound signals. CBL tests the quality of cement
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bond between casings and formation and indicates
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BOP is replaced with a series of valves to connect the
a remedial cement job can be completed before
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subsequent sections are drilled. Casings can be
resort when a blowout occurs. When the BOP closes,
similarly tested and repaired following each fracturing
vulnerabilities in casing and cement below could fail,
stage. Well integrity is inferred during operations by
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formations (an underground blowout). Proper design
annular pressures, as well as testing seals and valves
to maintain subsurface well integrity remains vital.
at casing joints (API 2009).

Despite the quality of the initial cementation
(indicated by an adequate CBL test), some wells
can still leak over time. One possible explanation
is the tendency of cement to shrink (Dusseault et
al 2000). Cement shrinkage may be caused by one
(or a combination) of several distinct mechanisms
associated with drying, cooling and autogenous
(sealed system) effects. A cement formulation that
is resistant to one mechanism will not necessarily
be resistant to another (The Concrete Society 2010).
Shrinkage can reduce radial stresses, weakening
cement bonds with the surrounding rock and


Shale gas extraction in the UK: a review of hydraulic fracturing

Shale gas extraction in the UK: a review of hydraulic fracturing

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