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House of Commons Environmental Audit Committee - Environmental Risks of Fracking

The House of Commons Environmental Audit Committee has launched an inquiry into the Environmental Risks of Fracking. Details of this inquiry, along with the Terms of Reference can be found on the government website. The submission produced by the Geological Society can be found below:

Submitted 18 December 2014

  1. The Geological Society is the UK’s learned and professional body for geoscience, with more than 11,500 Fellows (members) worldwide. The Fellowship encompasses those working in industry, academia and government with a broad range of perspectives on policy-relevant science, and the Society is a leading communicator of this science to government bodies, those in education, and other non-technical audiences.
  2. We have not attempted to answer all of the questions set out in the terms of reference. Our submission draws principally on the geoscience relating to potential environmental risks associated with shale gas development and hydraulic fracturing. 
  3. To establish and maintain public confidence in any shale gas exploration or production programme, it is important that all significant perceived risks and uncertainties are given serious consideration, whether or not they are considered to be material by technically expert communities. To do this effectively depends on risk identification, assessment and management (in particular, ensuring appropriate and effective regulation). We remain confident that, given sufficient care and attention, it is possible to locate and extract shale gas safely. It is for others to determine whether this should be done, which is a matter of economic, political and social judgment. Below we consider some of the potential risks and uncertainties which have been posited regarding shale gas exploration and production with respect to safety and local environmental impacts.

    Water Quality

  4. In the UK, groundwater provides 35% of our drinking water. Groundwater is also important to support surface water flow and regulate the health of ecosystems. Concerns have been raised about the possible contamination of groundwater by methane, fracking fluid chemicals, and dissolved contaminants in flowback water, as a result of shale gas operations.
  5. In the UK, most aquifers used for drinking water lie within the first 300 metres below the surface, while most fracking operations would take place at a depth of more than two kilometres. Assuming wells are properly constructed and well integrity is not compromised (see paragraph 6 below), contamination of groundwater through migration of methane and fracking fluids from shale formations to shallow aquifers through stimulated fractures could only take place if the fractures are able to propagate vertically through the intervening layers of rock. Analysis of fracking operations in the USA, combined with data obtained from natural fracturing of rocks, indicates that the probability of a stimulated fracture exceeding a height of 350 metres is around 1 per cent.1 The analysis suggests that if a separation distance of at least 600 metres is maintained between aquifers and fracture zones, the risk of a fracture propagating to the aquifer and causing contamination is extremely low. Confidence in this result would be increased by conducting similar analyses for UK shale formations. For more information on this subject, see the briefing note the Society published on Shale Gas (
  6. There are several aspects to well integrity, including well design, integrity of the cement bond between the casing and the well bore, and composition of the casing in the context of its ability to resist corrosion. If all these aspects are appropriately and effectively assessed, understood and regulated, it is possible to construct and operate wells without endangering human health or the local environment. A further source of potential contamination of near-surface groundwater is leakage from surface fracking fluid storage and processing facilities.

  7. There are recorded instances of methane in groundwater in the USA in areas where shale gas operations have taken place. A more likely cause than migration through fractures is methane leakage at the well site itself, due to poor design or construction, or subsequent damage. (Historically, onshore US hydrocarbons operations have not always been effectively regulated, and in some areas there is a lack of records relating to well design and construction.) Methane can also occur naturally in shallow groundwater. Geochemical analysis can distinguish this (biogenic) methane from thermogenic methane from deep shale formations. Baseline studies of methane in groundwater, such as that currently being carried out by the British Geological Survey (BGS) for areas of the UK likely to be prospective for shale gas, will enable any increase due to shale gas operations to be quantified.

    Water Supply and Disposal

  8. Between 9,000m3 and 29,000m3 of water is required to drill and carry out multi-stage fracturing of each well in US operations, with multiple wells often located on a single ‘well pad’. In areas where fresh water supplies are already under stress (or at times when this is the case), abstracting fresh water at this level for shale gas extraction may cause additional stress. For shale gas to meet 10% of UK gas demand would require 1.2-1.6 million m3 of water annually. However, this represents only about 0.01% of licensed annual water abstraction for England and Wales in 2010. Increasingly, it is possible to use saline or recycled water for shale gas extraction, and work is underway to develop better integrated water management solutions.
  9. Some of the fluid remains in the deep sub-surface, where it aids retention of the mechanical integrity of the rock. Between 20% and 80% returns to the surface as flowback water, where it must be managed safely. In small amounts, this can be disposed of in standard industrial water treatment plants. Larger volumes of fluid require specialist processing for disposal or re-use. Flowback water may contain Naturally Occurring Radioactive Materials (NORM) at low levels, as is the case in conventional oil and gas extraction and some areas of mining, and procedures for their effective management are well-established. The chemicals used in the fracking solutions are familiar to the hydrocarbons industry and we see no reason to believe that, given appropriate regulation, water cannot be sourced and disposed of without endangering human health or the local environment. The risk of mobilising natural uranium from source rocks has been raised in the research literature. We are not aware of any evidence of harm.

    Induced Seismicity

  10. The terms of reference for the inquiry refer to ‘risks to geological integrity’. It is not clear to us what this is intended to refer to. The potential for propagation of fractures (addressed at paragraph 5) might be seen as relating to geological integrity. Below, we comment on induced seismicity. If we have misunderstood and the committee has concerns about other aspects of geological integrity, we would be pleased to offer further comment or to respond to specific questions.
  11. Induced seismicity – the release of energy stored in the Earth’s crust triggered by human activity – is known to be caused by activities such as mining, deep quarrying, geothermal energy production and underground fluid disposal. In 2011, two small seismic events of magnitude 2.3 and 1.5 took place in Lancashire, UK, close to a fracking test site operated by Cuadrilla. Operations were suspended, and subsequent studies have suggested that hydraulic fracturing is likely to have been the cause, by reactivating an existing fault. This raised concern about the risk of further induced seismic events caused by fracking. The Department for Energy and Climate Change (DECC) subsequently gave permission for Cuadrilla to resume exploratory operations in Lancashire, with a ‘traffic light’ system in place, to give early warning of any further induced seismic activity.
  12. The maximum magnitude of any seismic event is dependent on the mechanical strength of the rock in which it occurs. The crust in most of the UK is relatively weak, and unable to store sufficient energy for large seismic events. This means that the largest natural earthquake we can expect is likely to be no greater than magnitude 6. However, based on our understanding of the mechanical strength of shale and case studies of fracking operations in the USA, it is extremely unlikely that seismic events induced by fracking will ever reach a magnitude greater than 3. It may be worth noting here that magnitude is measured on the Richter scale which is a base-10 logarithmic scale. Therefore, an earthquake with a magnitude of 6 (the largest expected in the UK) has a magnitude 1000 times greater than that registering at a magnitude of 3. However, this does not correspond to the energy release, where a difference in magnitude of 1 correlates to a ratio of 31.6. Therefore a magnitude 6 earthquake would result in ~31000 times more energy released than a magnitude 3 earthquake.
  13. Earthquakes at a magnitude of 3 are likely to be detectable by few people and are highly unlikely to cause any structural damage at the surface. To minimise the risk of seismic events even at this level, operators should avoid drilling through or near faults, and baseline micro seismicity should be monitored in real time before, during and after fracking in order to discriminate seismic events induced by human activity from naturally occurring events. Data on background levels of seismicity are available from the BGS. The monitoring of damage to well integrity, in addition to careful well planning to avoid such zones during any drilling operations, will help reduce the risk of seismic events. Monitoring of this kind would be a significant undertaking, and would incur cost and delays to any drilling operations. A benefit would be to help build public confidence as well as to mitigate operational and production risks.
  14. Micro-seismicity will result whenever large volumes of fluid are injected into rock – for instance, in carbon capture and storage (CCS) or geothermal energy generation. Many other drilling operations also induce micro-seismicity. This is well known and understood in the hydrocarbons industry, and any associated risks are already effectively managed in existing exploration and production contexts. This is therefore not an unfamiliar risk to subsurface scientists and engineers. Moreover, operating companies routinely draw on background knowledge derived from other applications in order to identify relevant uncertainties and then to minimise and manage such risks, especially in planning well locations to avoid significant faulted or unstable zones.

  15. We note that real time event detection and calibration is not straightforward. Good surface and/or borehole arrays are needed, and further study on the design of site surveys and monitoring arrays may be required. While the automated detection of larger events is done routinely, detecting low magnitude events is not yet routine. It is also important to note that interpreting and assessing microseismic data carries with it uncertainty, and such data may be open to differing interpretations by different scientists – they represent a valuable tool, but will not always provide clear-cut unequivocal answers. The licensing regime should require public deposit of such data after a reasonable period (as is done for North Sea hydrocarbon seismic survey and well data – downhole geophysical logs, cuttings, core, etc), so that they can be inspected by the wider scientific community.
  16. It is important to have a detailed understanding of the local structural geology and geomechanical characteristics of the subsurface (both overburden and potential shale gas reservoir), to improve identification and characterisation of faults, and modelling and mitigation of induced seismicity (as well as other possible impacts). Smaller volumes of fracking fluid should be injected initially. Simple models of seismic activity, its propagation and its relation to ground motions are likely to be inadequate. Other factors which may have a significant effect are stress anisotropy (i.e. directional variation in physical properties of shale rocks, and therefore their behaviour under stress), the variety of source mechanisms and radiation patterns for seismic events, site conditions and potential ground acceleration. The latter can be established and incorporated in a hazard analysis (with a suitable baseline survey). There may be lessons to learn from other sectors, regarding the perception of motion by humans and impacts on buildings and infrastructure. (See, for example, Bommer, J.J. et al (2006), Control of hazard due to seismicity induced by a hot fractured rock geothermal project, Engineering Geology 83 287-306.)
  17. It is important that a consistent regulatory framework be established which is applicable universally, and also that variation of specific details appropriate to areas with different geology be carefully thought through and made explicit. We also note that other countries in Europe are likely to pay close attention to policy-decisions and the basis for regulation in the UK, heightening the need for careful peer review and expert engagement.

    Social and Visual Impact

  18. This is a possible public concern regarding onshore hydrocarbons exploration and production generally. The UK hydrocarbons industry has demonstrated that it can successfully exploit resources while meeting the highest environmental and social standards. Wytch Farm, the largest onshore oil field in Western Europe, was discovered by British Gas in the 1970s and operated by BP since 1984 until the sale of its interest to Perenco. It is located in one of the world’s most famous and sensitive regions of outstanding beauty and natural interest (not least because of its geology and geological heritage), which includes the Jurassic Coast World Heritage Site, designated wetlands of international importance, and national nature reserves. World standards in environmental protection and community engagement have been set at Wytch Farm, using horizontal drilling at distances of more than 10km, keeping the size of well sites to a minimum, and adding considerably to the capital cost of the gathering station by restricting height of facilities to below the tree line, in order to minimise environmental and visual impacts. It is worth noting that in the case of Wytch Farm, it was possible to conceal production facilities within an existing plantation of mature trees, an advantage that would not apply everywhere in the areas of potential shale gas operations. Members of the public looking out over the area are likely to be unaware of the existence or scale of the Wytch Farm operations in question. The key is to set regulations which reflect the required environmental and social standards, and also to minimize the footprint and disturbance caused by any operational activities. This is well within the scope of industry, given a suitably informed and expert regulatory environment to ensure that appropriate standards are defined and adhered to. 

    Impact on Carbon Emissions

  19. The July 2012 report on ‘Climate impact of potential shale gas production in the EU’, prepared for the European Commission by the sustainability consultancy AEA, provides a useful overview of the widely varying conclusions of existing studies of carbon emissions resulting from the extraction and use of shale gas. It notes that this variation is largely due to authors’ selection of narrow sets of data, different interpretations of such data and different framing assumptions. It also points out that ‘overall, the emissions from shale gas are dominated by the combustion stage’ (p iv). Shale gas and conventional natural gas have the same composition (mainly methane, though in both cases the exact proportions of gases present will vary), albeit found and extracted in different geological settings, so the emissions from their combustion are the same. Emissions at stages prior to combustion include fugitive emissions (i.e. gas which escapes into the atmosphere from the well or through equipment at the well site) of methane (a considerably more potent greenhouse gas than carbon dioxide) at the point of extraction, those resulting from processing (e.g. liquefaction), and from its transmission/transport. Fugitive emissions have been found in some studies to be higher for shale gas than for conventional gas.
  20. Looking at the range of studies, it is uncertain whether total emissions from shale gas are greater or less than those from imported conventional gas, for instance. In fact this is likely to vary from case-to-case, as the level of fugitive emissions will depend on factors such as well integrity and the design of production processes, and those resulting from transport will depend on its mode and distance. As with other potential environmental impacts of shale gas extraction, appropriate and effective regulation is required to minimise fugitive emissions. The comparison with coal is more clear-cut – emissions resulting from the extraction and use of shale gas are considerably less.
  21. This does not mean that natural gas (whether conventional or unconventional) can be extracted and used with impunity, in the absence of carbon capture and storage (CCS). Both nationally and globally, we will continue to be dependent on fossil fuels for several decades, irrespective of whether we extract shale gas at scale, and if the resulting carbon emissions are not sequestered this is likely to have very significant negative effects on our environment. The geological record contains abundant evidence of the environmental changes associated with periods of rapid release of carbon into the atmosphere in the deep past. (See the Geological Society’s Climate Change Statement at We agree with the comments of the chair of the Energy and Climate Change Committee that given sufficient care and attention, shale gas could be safely produced, but that the emergence of shale gas as a major fossil fuel increases the ‘urgency of bringing carbon capture and storage technology to the market and making it work for gas as well as coal’ (Select Committee Announcement 45a, 23 May 2011).

    Regulation, Planning and Research

  22. Regulation of shale gas exploration and production should be scientifically well-founded, with the basis for thresholds and detection limits transparently justified. It should address all aspects of safety and perceived risk in respect of:

    • the siting, planning and drilling of wells
    • hydraulic fracturing and associated processes including water management (access and disposal)
    • subsequent gas production and impact on carbon emissions
    • baseline data gathering and characterisation before operation, and monitoring during stimulation and subsequent production

    Regulation should be effectively applied by appropriately skilled and resourced regulators. Responsible hydrocarbons companies (which share government’s interest in building public confidence in their operations) welcome such regulation.
  23. Such a rational framework for regulation should inform both policy decision-making, and subsequent implementation. In so doing, it is vital to take a holistic view. As noted above, the interaction of seismic activity and local-scale structural geology is complex. It is important to consider issues such as the potential effect of seismic activity on gas migration, well integrity and the contamination of groundwater. These interdependencies should not call into question whether shale gas can be extracted safely. Rather, they should inform the regulatory regime, economic, political and social decision-making, and the programmes of research required to underpin these.
  24. We note that the Environment Agency is actively monitoring the status of shale gas exploration and production, and has found its existing regulatory framework to be fit for purpose for the current phase of exploration. They have undertaken to keep this framework under review if and when a UK shale industry develops further. They will also ensure that UK regulation is compliant with the European Commission January 2014 Recommendation setting minimum standards and monitoring principles in respect of a wide range of potential risks, including those discussed above. 
  25. High quality research is underway across the UK’s universities and the BGS, also drawing on the expertise of industry partners, to deepen our understanding of the geoscience and engineering relating to many of the potential risks addressed above. We welcome the £31m investment for sub-surface research test centres, for energy technologies including shale gas, to be run through the Natural Environment Research Council, announced in the December 2014 Autumn Statement. We also note the continuing work of ReFINE (Researching Fracking in Europe -, a university consortium which is addressing a number of the issues raised in the call for evidence. Finally, the Geological Society, working with Global Event Partners, is hosting the second Shale UK conference (4-5 March 2015), aimed at informing a broad audience including researchers, policy-makers, industry decision-makers, regulators and representatives of local communities about the geoscience relevant to shale gas exploration, extraction and environmental management.


1 Davies, R.J., et al., Hydraulic fractures: How far can they go?, Marine and Petroleum Geology (2012)