Unconventional oil and gas policy: SEA

6 Water

What are the environmental effects of unconventional oil and gas development on water?

6.1 Unconventional hydrocarbon extraction can both produce wastewater and consume water resources.

6.2 The wastewater produced by unconventional oil and gas developments is also referred to as ‘flowback and produced’ (FP) waters^[114]. The difference between flowback water and produced water is the time spent in the well; flowback water usually refers to the return of injected fluids following hydraulic fracturing, while produced water is formation water that is high in gas and oil^[115] or water produced due to the pumped abstraction of water directly from coal beds. Coal bed methane (CBM) development generally does not require the injection of fluids or hydraulic fracturing^[116,117].

6.3 Unconventional oil and gas development can also consume water. Shale gas and shale oil operations require water for the hydraulic fracturing process. In Scotland, the vast majority of water is sourced from surface water resources, although the industry may wish to abstract groundwater for logistical reasons.

6.4 Coal bed methane (CBM) operations involve a dewatering process. During this process, the coal bed methane is extracted by pumping out the water in the reservoir, which decreases the water pressure, allowing the gas to detach from the coal reservoir and well up to the surface^[118].

6.5 The potential environmental effects of unconventional oil and gas development on water arising from the different stages and activities associated with unconventional oil and gas development are identified as:

• Direct water pollution arising from exploration, appraisal, production and decommissioning:
• Water contamination caused by produced water during production;
• Water pollution caused by flowback waters during production;
• Gas and fluid leakage associated with poor well construction during exploration, appraisal and production;
• Aquifer cross-contamination due to poor borehole construction during exploration, appraisal and production;
• Accidental releases of hazardous materials;
• Surface spills from storage tanks;
• Contamination that could arise from the construction and removal of infrastructure;
• Leaks along the casing of poorly constructed and decommissioned unconventional oil and gas wells.
• Abstraction of water for hydraulic fracturing during the exploration, appraisal and production stages with impacts on:
• Water availability and supply.
• Indirect water pollution arising from abstraction of water for hydraulic fracturing during the exploration, appraisal and production stages:
• intrusion of saline water into waterbodies as a result of water extraction.

How do these effects relate to the current pressures and trends?

6.6 In recent decades, significant improvements in water quality have been observed in many rivers, canals and estuaries due to decreases in the releases of environmental pollutants. Recent data^[119] shows that 80% of groundwaters in Scotland were at good status in 2016. In addition, 62% of surface waters (rivers, lochs, and estuaries) were at good status or better in 2016^[120]. Rivers across Scotland’s Central Belt and East Coast require further work in order to ensure that they achieve ‘good or better’ overall status under Scotland’s overarching target framework for waterbodies^[121]. Figure 2a and 2b, Appendix 1 illustrate the water quality across Scotland and the Central Belt, and illustrates that several areas of poor water quality coincide with the area prospective for unconventional oil and gas development.

6.7 Key pressures on water quality originate from human activity. Climate change could also affect water quality, it could extend the growing season, which could place additional pressures on water quality as agriculture is a key source of environmental pollutants^[122]. Changes in water availability from warmer drier summers and warmer wetter winters could also impact on water quality.

What current regulatory processes control these effects?

6.8 There is legislation in place to control certain impacts of unconventional oil and gas developments on the wider water environment.

6.9 At the European level, the REACH Enforcement Regulations 2008^[123] require that all additives in fracturing fluids that exceed the one metric tonne threshold and other requirements set by REACH Regulation must be registered at the European Chemicals Agency by the manufacturer or importer.

6.10 In Scotland, the Town and Country Planning (Environmental Impact Assessment) (Scotland) Regulations 2017^[124] relate to the assessment of the impact of certain public and private projects on the environment through the planning system.^[125] This would require consideration of impacts on water quality and quantity where unconventional oil and gas developments are of a size and scale to require EIA.

6.11 In the UK, the Borehole Sites and Operations Regulations 1995^[126] requires notifications to be made to HSE about the design, construction and operation of wells. In addition, well operators must provide HSE with regular reports of any activities on the well where there is a risk of an unplanned release of fluids from the well. In such circumstances, they must appoint an independent well examiner to undertake regular assessments of well integrity. Under the 1995 Regulations, the HSE also requires that wells are designed and construction with well abandonment in mind (DCR Regulation 15). During the decommissioning phase, operators must notify the HSE before wells are abandoned and show that the process complies with Oil and Gas UK guidelines and the requirements of the DCR.

6.12 Any unplanned release of fluids from an oil or gas well must also be reported to HSE under Schedule 2, Part 1, Section 20 of the Reporting of Injuries, Diseases and Dangerous Occurrences Regulations 2013^[127].

6.13 The Control of Major Accident Hazards Regulations 2015 (COMAH)^[128] seek to prevent major accidents involving dangerous substances and limit the consequences to the environment, including the water environment. If COMAH applies, the operator will be required to identify their major hazard scenarios and demonstrate to the Competent Authority that they have taken control measures to prevent major accidents and made arrangements for mitigatory action in the event of an accident occurring. The enforcement authority (HSE and SEPA) can prohibit operation where these measures are seriously deficient.

6.14 If naturally occurring radioactive material (NORM) is above threshold levels set by the Radioactive Substances Act 1993 (RSA 93)^[129], contaminated vessels and pipework must be taken to specialist clean-up facilities, where the radioactive scale is removed before disposal in a UK landfill. The management of NORM containing wastes, including their disposal to the environment, is regulated by SEPA. The disposing of produced or ‘flowback’ waters is tightly regulated in Scotland. The production of „flow-back‟ fluid from hydraulic fracturing is a mining waste activity, relevant to The Management of Extractive Waste (Scotland) Regulations 2010. Disposing of produce or flowback waters will be controlled through planning permission for the site through an agreed waste management plan. Operators will need to have a waste management plan in place, and be able to demonstrate to planning authorities how they will store and dispose of wastes safely without causing pollution to the environment.^[130]

6.15 Through the Water Environment (Controlled Activities) (Scotland) Regulations 2011 (CAR)^[131], the operator requires an appropriate authorisation for specific activities with the aim of preventing significant adverse impacts on the water environment. The following activities all require CAR authorisation:

• the construction of the borehole;
• the discharge of fracturing fluid to ground or surface water, including assessing hazards presented by fracturing fluids on a case-by-case basis;
• ground or surface water abstractions.

6.16 Where the Pollution Prevention and Control (Scotland) Regulations 2012^[132] apply, SEPA will require the operator to effectively manage risks to ground water resources.

6.17 Scotland’s regulatory framework comprises regulation to mitigate the risks of surface spills of fracturing fluid i.e. caused by accidental release. In the UK, there are systems in place to manage the impact of chemical spillage in the event of a traffic accident. These controls would reduce, but not fully eliminate, such risks.

6.18 Currently, there is no specific legislation for monitoring once a Petroleum Exploration and Development Licence (PEDL), Controlled Activities Regulations (CAR) licence or Pollution Prevention and Control (PPC) licence is surrendered. There is a need for improved baseline monitoring of environmental data to allow any environmental impacts to be effectively identified^[133]. A CAR license cannot be surrendered until SEPA is satisfied there is no risk to the environment.

6.19 Regulatory consents incorporate best practices in order to mitigate spills and leakages. These include using non-hazardous chemicals wherever possible, storing them away from surface waters and important aquifers, ensuring sites are protected with impermeable liners and ensuring all stores have double walls as a precaution against leaks^[134]. In the event that surface spills or leakages occur, there is appropriate legislation already in place to ensure remediation^[135].

6.20 An abstraction is the removal or diversion of water from the natural water environment, by a variety of means. Abstractions are regulated by the Water Environment (Controlled Activities) (Scotland) Regulations 2011– more commonly known as the Controlled Activity Regulations (CAR) and requires authorisation from SEPA, and ensures the responsible management of water resources.^[136]

What stages of unconventional oil and gas development result in these effects, what is the nature and significance of these effects?

Direct water pollution

Business as usual – shale oil and gas extraction

6.21 Contamination caused by produced water is a potential issue associated with unconventional oil and gas development. Research has shown that the chemistry of produced water is consistent with that of water contained in coal beds at depth with substances including: chloride, iron, aluminium, nickel, zinc, lead and a number of organic compounds (benzene, xylene, and naphthalene)^[137]. Produced water also contains high brine levels, with concentrations above that of seawater^[138]. In some instances, produced water may be contaminated with naturally occurring radioactive materials (NORM). NORM are present in a wide range of geological formations, including oil- and gas-bearing rock strata. Produced water abstracted from coal seams may contain NORM. In addition, NORM are likely to be present in unconventional oil and gas operations as insoluble sediments and scales that adhere to the surface of pipework (of both CBM developments and hydraulic fracturing operations)^[139].

6.22 Contamination caused by produced water could occur during the exploration, appraisal and production stage, which together could occur over a period of approximately 20 years for an individual development^[140]. Should these effects occur, it is judged that the duration of these impacts is uncertain, depending on the type(s) of naturally occurring radioactive material(s) present, the geochemistry of the reservoir, the volume of water circulating through the reservoir^[141] and the sensitivity of the receiving environment.

6.23 Due to the existing regulatory regime, the environmental impacts of water contamination caused by the disposal of produced water should be minimal, unless there is illegal disposal of fluid.

6.24 Water pollution caused by ‘flowback’ water is a potential risk associated with hydraulic fracturing development. During the hydraulic fracturing process, water is injected into the shale at high pressure in order to create, or enlarge, tiny fractures in the rock. Some of the water that is injected into the shale rock returns to the surface as ‘flowback water’^[142]. Typically around 25% of the water injected will return to the surface over a period of weeks, or potentially a few months. ‘Flowback’ water is very saline and has a high mineral content – notably high levels of sodium, chloride, bromide and iron, as well as higher values of lead, magnesium and zinc^[143]. It may also contain NORM, inorganic materials and organic matter^[144].

6.25 Water pollution caused by ‘flowback’ water could occur during the exploration, appraisal and production stage, which together could occur over a period of approximately 20 years for an individual development^[145]. Should water pollution caused by ‘flowback’ water occur, it is judged that the duration of these impacts is uncertain, depending on the type(s) of naturally occurring radioactive material(s) present, the chemical composition of the hydraulic fracturing fluid, the geochemistry of the reservoir, the volume of water circulating through the reservoir^[146] and the sensitivity of the receiving environment.

6.26 There is the risk of surface water contamination if ‘flowback’ water is not treated properly before disposal^[147]. Due to the existing regulatory regime, the environmental impacts of water contamination caused by the disposal of ‘flowback’ water should be minimal, unless there is illegal disposal of fluid. It is important to note that the scale of these effects is likely to be greatest under the KPMG high production scenario, which has the highest number of pads and greatest number of wells developed per pad.

6.27 Gas and fluid leakage associated with poor well construction could have the potential to adversely impact local water quality. In certain circumstances, hydrocarbons and other well fluids can migrate out of the well and into the wider environment. It has been suggested that it may also be possible for gas in the shale formation to escape into ground water following fracking activities. However, the likelihood of widespread significant releases by this mechanism has been questioned in literature, as no such releases during the hydraulic fracturing process have been recorded^[148,149].

6.28 Gas and fluid leakage caused by poor well construction can occur during the exploration, appraisal and production stages and following well decommissioning. These effects could therefore occur over a period well in excess of 20 years. Should gas and fluid leakage occur, the duration of these impacts is uncertain, depending on the construction of the well, the nature of the geological formation in question and the sensitivity of the receiving environment. The main waterbodies at risk from gas and fluid leakage from wells are^[150]:

• shallow groundwater;
• groundwater bodies at greater depth;
• drinking water.

6.29 Well integrity is important to ensure that no gas leakage occurs during the production stage or injected fluid leakage during the injection period of the hydraulic fracturing operation. Problems involving well construction, particularly well casing and cementing failures are the most common reported sources of water contamination^[151].

6.30 It is important to note that there are differences between the number of well casings, and the extent to which these are cemented in place. In the US, it is common to have two strings of casings. At a minimum, the cement should extend above any exposed water or hydrocarbon bearing zones. In some states, such as Pennsylvania and Texas, there is a requirement to cement casing to approximately 75ft below any aquifers. In the UK, standard practice is to have three strings of casing with at least two passing through (and thereby isolating) any freshwater zones. Best practice in the UK is to cement casings all the way back to the surface^[152]. In addition, the details of local geology in Scotland remain unclear – making it difficult to draw any conclusions regarding the scale of any potential impacts^[153]. As a result, findings drawn from U.S. case studies cannot be assumed to represent the Scottish situation due to differences in regulatory regimes as well as contrasts in geology. Therefore, there is uncertainty as to the extent to which result from US case studies could apply in Scotland^[154].

6.31 Another key issue is aquifer cross-contamination due to poor borehole construction, particularly in the cased and cemented zone of a borehole. Movements of pollutants that depend on geological and hydrogeological conditions may result in the rise and the lateral spreading through geological strata via an aquifer^[155]. This is especially true in the shallower subsurface, where such leaks could potentially contaminate freshwater aquifers^[156].

6.32 Aquifer cross-contamination due to poor borehole construction can occur during the exploration, appraisal and production stage. These stages together could occur over a period of approximately 20 years for an individual development. Should aquifer cross-contamination occur, it is judged that these effects would be effectively permanent, although it is recognised that over a long timescale, these effects can be reversed. The duration of these impacts is uncertain, depending on the construction of the borehole and the nature of the geological formation in question, the nature of the hydrology near the cased and cemented zone of a borehole, the structure of the (sub)surface and the sensitivity of the receiving environment.

6.33 The risk of direct migration of methane or other components from the unconventional oil and gas well to aquifers is judged to be minimal, and only considered significant if fracking affects the insulating qualities of wells. Due to existing legislation for well construction and design, these risks are minimised but remain a point of concern^[157].

6.34 Surface water contamination caused by accidental releases of hazardous materials and wastewater spills during transportation. Truck accidents could potentially lead to chemical or wastewater spills which could include fracturing fluid, additives, ‘flowback’ water and/or produced water^[158]. In the event of an accidental spill, fluids can run off into surface water and seep into groundwater^[159].

6.35 Surface water contamination caused by accidental releases of hazardous materials and wastewater spills during transportation can occur during the production and decommissioning stage, which together could occur over a period of approximately 20 years. Should surface water contamination occur, it is judged that the duration of these effects is uncertain, depending on the type of material spilled, the volume of material spilled, and the proximity of the spill to surface waters and other sensitive systems^[160].

6.36 There is regulation to mitigate the risk of accidental releases of hazardous materials, and therefore the environmental impacts of water contamination from these should be minimal. This risk increases under the higher production scenarios. The likelihood of pollution incidents that contaminate surface water increases as the number of drilling sites increases^[161]. Therefore, the scale of these effects is likely to be greatest under the KPMG high production scenario and lower for the central and low scenarios.

6.37 Surface water spills from storage tanks could have the potential to adversely impact upon water quality. These spills include fluids and chemicals used in the unconventional oil and gas process, or produced water and ‘flowback’ water^[162]. For instance, the water injected into the shale rock during the hydraulic fracturing process contains several substances. Typically, water injected into the shale rock during the hydraulic fracturing process contains proportions of sand (5%) and chemicals (1%)^[163].

6.38 Surface spills from storage tanks can occur during the exploration, appraisal and production stage. These stages together could occur over a period of approximately 20 years for an individual development. Should surface spills from storage tanks occur, it is judged that the duration of effects would be temporary, depending on the frequency of spills, the type of material spilled, the volume of material spilled, and the proximity of the spill to surface waters and other sensitive systems^[164].

6.39 There is regulation to mitigate the risk of accidental releases of hazardous materials, and therefore the environmental impacts of water contamination from these should be minimal. This risk increases under the higher production scenarios. The likelihood of pollution incidents that contaminate surface water increases as the number of drilling sites increases^[165]. Therefore, the scale of these effects is likely to be greatest under the KPMG high production scenario and lower for the central and low KPMG scenarios.

6.40 Another risk is related to contamination that could arise from the construction and removal of infrastructure – particularly that which could link between different boreholes across the drilling area^[166].

6.41 Boreholes are drilled for core sampling and for extracting oil, gas and water. The effects of borehole construction could occur during exploration, appraisal and production.

6.42 Poorly constructed and decommissioned oil and gas wells can develop leaks along the casing after production has ceased. Such leaks often take years to unfold after decommissioning, allowing hydrocarbons and other well fluids to eventually migrate out of the well and into the environment. During the decommissioning stage, there is also the risk of leaks in tanks and pipework which could potentially contaminate the ground^[167].

6.43 Leaks from decommissioned wells can occur during the decommissioning stage, which usually occurs over a period of 2-5 years, however, leaks often take years to unfold after decommissioning. Should leaks occur, it is judged that these effects would be effectively permanent, depending on the nature of the water environment and geological structures surrounding the well, and the construction of the well.

6.44 The scale of these effects on the water environment is likely to be greatest under the KPMG high production scenario, which has the highest number of pads and greatest number of wells developed per pad. These effects are likely to be lower for the central and low KPMG scenarios.

6.45 Taking account of the existing regulatory framework, it is judged that the potential impacts of direct water pollution occurring as a result of poor well construction and well leakage in decommissioned wells may result in minor negative uncertain effects.

6.46 It is judged that the potential impacts of direct water pollution from all of the above sources may result in a cumulative potential significant negative but uncertain effect.

Business as usual – CBM

6.47 The effects in terms of direct water pollution for shale oil and gas extraction are broadly similar for CBM. Based on this conclusion the potential effects on the water environment are also judged to be significant negative.

Pilot project

6.48 The effects of a pilot project on the water environment could vary significantly, depending on its location. Compared to the ‘Business as usual’ alternative, the development of a single pilot location would reduce the area over which the effects on the water environment may occur. The risk of direct impacts on the water environment is judged to be significant in areas of high sensitivity to water pollution. This includes resources which rely on high water quality such as biodiversity.

6.49 The rural pilot is assumed to be in an area of higher water quality, although its connectivity to sensitive areas is not specified. Therefore potentially significant negative effects on local water quality have been identified.

6.50 Compared to a rural pilot which is assumed to be in an area of higher water quality, the effect of water pollution may be greater in the semi urban pilot area which is assumed to be in an area of moderate water quality and has direct pathways to an area of international biodiversity importance, and a secondary significant negative effect is identified, reflecting the impacts on the internationally important biodiversity site. The urban fringe pilot area is assumed to be in an area of poor water quality and the development will add to existing water quality issues, and a minor negative effect is identified.

Preferred policy position

6.51 The preferred policy position means that adverse impacts of direct water pollution on water quality from shale oil and gas production (greatest for the KPMG high production scenario, and less for the central and low scenarios), CBM production and a pilot development, would be avoided.

6.52 This is considered to be a significant positive effect.

Water abstraction and supply and indirect water pollution arising from abstraction

Business as usual – shale oil and gas

6.53 Water is typically the main component in hydraulic fracturing fluids. During large-scale shale gas extraction, large quantities of fracking fluids may be required. In some locations, this has been recorded as resulting in shortages of local water supplies e.g. for drinking water and agriculture^[168]. The impacts of climate change may further exacerbate this problem^[169]. Surface water and groundwater abstraction associated with unconventional oil and gas developments also has the potential to lead to the intrusion of saline water into non-saline groundwater^[170].

6.54 Due to the regulatory control of water abstraction by SEPA, it is assumed that levels of abstraction would be controlled within environmental limits in order to maintain the quality of the local water environment. Should uncontrolled abstraction occur, this could result in significant negative effects on the local water environment^[171]. Under the KPMG high scenario, the requirement for water would be greatest due to the high number of wells, and the cumulative effect of this could result in competing demand for water within a local area. This could impact on the local availability of water and the ecological status of waterbodies. Although there is potential risk of uncontrolled abstraction, this is viewed as low. Therefore, in light of the regulatory control provided by SEPA, adverse impacts from abstraction are judged to be negligible.

Business as usual – CBM

6.55 CBM extraction uses a dewatering process, and where hydraulic fracturing is not required for extraction, does not require water. However, the CBM dewatering processes which remove groundwater can result in the intrusion of saline water into waterbodies. This can occur during the exploration, appraisal and production stage, which could occur over a period of approximately 20 years. It is judged that the impacts would be effectively permanent, although it is recognised that over a long timescale, these effects can be reversed. However, this largely depends on the nature of the geological processes and interactions between rocks, the nature of the surrounding water environment and the sensitivity of the receiving environment. The areas at highest risk of saltwater intrusion include^[172]:

• close to the coast;
• where there is a low to moderate slope;
• on peninsulas or in areas with a limited source area for groundwater recharge;
• where there is a high density of wells;
• where there are high rates of pumping from a single well or from multiple wells in a coastal area;
• where the static (non-pumping) groundwater level is at or below sea level.

6.56 The intrusion of saline water into waterbodies could impact on water quality with locally significant effects. Secondary effects from salinisation may occur in relation to soil quality, biodiversity and material assets. The regulatory control provided by SEPA should ensure that these impacts are negligible.

Pilot

6.57 Should uncontrolled abstraction take place, this could result in locally significant effects on water quality and availability. Compared to a rural pilot which is assumed to be in an area of higher water quality, the effect may be greater in a semi urban pilot area which is assumed to be in an area of moderate water quality and has direct pathways to an area of international biodiversity importance, and a secondary negative effect could occur, reflecting the impacts on the internationally important biodiversity site. The effect may also be greater in an urban fringe pilot area which is assumed to be in an area of poor water quality. Reflecting the regulatory control provided by SEPA a negligible effect is identified.

Preferred policy position

6.58 The environmental effects of the preferred policy position are the avoidance of the risk of effects resulting from water shortages caused by uncontrolled abstraction of water and impacts on water quality resulting from uncontrolled abstraction. This risk is however acknowledged as low, and the overall effect is judged to be negligible.

Cumulative, secondary and synergistic effects

Business as usual– shale oil and gas

6.59 The cumulative effects on the water environment from shale oil and gas extraction include the risk of direct water pollution, the risk of reduced water flow arising from water abstraction, and the secondary effect of indirect water pollution resulting from saline intrusion following water abstraction. Reflecting the potential scale of development under the KPMG scenarios, significant negative cumulative effects are identified for the water environment. The effects of reduced water levels as a result of abstraction could also result in negative synergy as a result of further exacerbation of the effects of direct water pollution as a result of reduced dilution of pollutants. Secondary effects from salinisation may occur in relation to soil quality, biodiversity and material assets. Impacts on soil quality and biodiversity could result in significant negative effects.

Business as usual - CBM

6.60 The impacts described above could also occur in relation to CBM, but over a smaller area, reflecting the development of two CBM pads. Minor negative effects are identified.

Pilot

6.61 Secondary effects from salinisation may result in effects with greater significance on resources such as soil, biodiversity and material assets, and potential locally significant effects could occur, with minor negative effects identified overall.

Preferred policy position

6.62 The timeframe for the avoidance of these additional effects is approximately the next 40 years reflecting the timescale of unconventional oil and gas development described in the KPMG scenarios. The avoidance of these effects is judged to be permanent within the context of the SEA. The scale of avoidance of effects reflects the geographic area identified as prospective for shale oil and gas, across the Central Belt of Scotland.

6.63 The preferred policy position means that adverse impacts on the water environment associated with shale oil and gas production (greatest for the KPMG high production scenario, and less for the central and low scenarios), CBM production and, to a lesser extent, a pilot development, would be avoided.

6.64 In conclusion, although the water environment of the Central Belt of Scotland will continue to face existing pressures, the preferred policy position means that additional pressures on water which could directly result from unconventional oil and gas development in Scotland would be avoided. This is considered to be a significant positive effect.

Scope for further mitigation

6.65 The assessment results are based on the application of existing regulatory controls. The evidence base includes information on a number of processes which could be implemented to reduce the scale of impact on the water environment. These could reduce the overall potential scale of effect from unconventional oil and gas development, and therefore the associated scale of effect avoided as a consequence of the preferred policy position.

6.66 The applicability and practicality of many of these additional measures will be determined at a site specific level so it is not possible to draw firm conclusions as to the extent to which they would mitigate predicted effects successfully.

6.67 The evidence base includes information on a number of processes which could be implemented to reduce the scale of impact on the water environment. The implementation of these measures would reduce the overall scale of adverse effects avoided.

6.68 Potential measures include:

6.69 Contamination caused by produced water and flowback water – there are a number of feasible ways to process flowback and produced (FP) water:

• Through the treatment of the wastewater so that it can be returned (back) to the environment. For instance, a crystallisation plant was recently commissioned in Pennsylvania (US) that is able to convert wastewater into water that meets current standards for water discharge in the US. The salt that is extracted during the process can also be used as road salt. The crystallisation plant in Pennsylvania is the first of its kind, and is more efficient economically and environmentally compared to more conventional wastewater treatment plants. Efforts are currently undertaken to further refine existing techniques or invent new approaches to fully or partially reuse wastewater.
• Injection of the wastewater into an empty gas field.
• Reuse of wastewater in subsequent fracking activities.

6.70 In addition, there are various substitutes that can be used to (partially) replace water in hydraulic fracturing fluids – carbon dioxide, LPG and/or propane being the most commonly used substances in the US and Canada. However, it is recognised that alternative substances have their respective disadvantages. For instance, they are often harmful or hazardous by nature (e.g. LPG) and their effect and risk is insufficiently known as nearly all alternative substances are hardly used or at the experimental stage.^[173]

6.71 Gas and fluid leakage associated with poor well construction – ensuring well integrity is highly dependent upon the application of best practice standards for well design and construction. In addition, a significant reduction in risks can be achieved by using monitoring technology so that remedial measures can be taken at an early stage. Examples include fibre optic sensing techniques including Fibre Bragg gratings (FBGs), Distributed Temperature Sensing (DTS) and Distributed Acoustic Sensing (DAS). Recent evidence suggests that fibre optic sensing technology has existed for decades, but most techniques are not yet mature for commercial deployment in the unconventional oil and gas industry. DAS has matured most rapidly, as is currently deployed on a commercial basis for selected geophysical and flow applications following a recent trial^[174].

6.72 Aquifer cross contamination – further development of high resolution sensors for monitoring could be used to prevent or reduce methane migration to aquifers.

6.73 Accidental releases of hazardous materials – increased traffic safety measures could help to reduce the number of vehicles carrying hazardous substances getting involved in traffic accidents.

6.74 Surface spills – geotextiles and geo-synthetics can be used on surfaces to reduce the risk of surface water pollution. It is important to note that geotextiles and geo-synthetics are already available, but are not yet widely used.

6.75 Borehole leaks – there are other ways to mitigate or limit the effects caused by the contamination of fracking fluids; the advancement of alternative hydraulic fracturing and drilling techniques may increase the efficiency of the hydraulic fracturing process so that the use of hazardous chemicals can be reduced or avoided.

Table 6.1: Summary of effects on Water

Environmental impact	Alternative	Potential scale of development	Timescale when effect may occur	Duration of effect	Predicted effect taking account of existing regulation	Key areas of uncertainty
Direct pollution	Business as usual– shale oil and gas extraction	Major	Short to long term	Permanent	A significant negative effect is identified reflecting the range of potential sources of direct water pollution.	Areas of uncertainty include the potential level of contamination by different pollutants, and the likelihood of contamination from different sources.
	Business as usual– coal bed methane extraction	Minor	Short to long term	Permanent	A significant negative effect is identified reflecting the range of potential sources of direct water pollution.
	Pilot project	Low	Short to long term	Permanent	A significant negative effect is identified for rural and semi urban pilots, with a minor negative effect on the urban fringe pilot.
	Preferred policy position	None	Short to long term	Permanent	A significant positive effect is identified reflecting the avoidance of significant negative effects.
Water abstraction and supply, and indirect water pollution from abstraction	Business as usual– shale oil and gas extraction	Major	Short to long term	Permanent	A negligible effect is identified reflecting the regulatory control provided by SEPA.	Occurrence of uncontrolled abstraction
	Business as usual– coal bed methane extraction	Minor	Short to long term	Permanent	A negligible effect is identified reflecting the regulatory control provided by SEPA.
	Pilot project	Minor	Short to long term	Permanent	A negligible effect is identified reflecting the regulatory control provided by SEPA.
	Preferred policy position	None	Short to long term	Permanent	A negligible effect is identified reflecting the avoidance of negligible effects.
Cumulative effects	Business as usual– shale oil and gas extraction	Major	Short to long term	Permanent	Significant negative cumulative effects are identified for the water environment reflecting the potential scale of development under the KPMG scenarios.
	Business as usual– coal bed methane extraction	Minor	Short to long term	Permanent	Minor negative effects are identified reflecting the scale of development over a smaller area
	Pilot project	Minor	Short to long term	Permanent	Minor negative effects are identified overall. Salinisation may result in effects with greater significance on resources such as soil, biodiversity and material assets, and potential locally significant effects could occur.
	Preferred policy position	None	Short to long term	Permanent	A significant positive effect is identified reflecting the avoidance of significant negative effects.