Loveless Sian E, Bloomfield John P, Ward Robert S, Hart Alwyn J, Davey Ian R, Lewis Melinda A
1British Geological Survey, Maclean Building, Crowmarsh Gifford, Oxon OX10 8BB UK.
Environment Agency, Horizon House, Deanery Road, Bristol, BS1 5AH UK.
Hydrogeol J. 2018;26(6):1975-1987. doi: 10.1007/s10040-018-1737-y. Epub 2018 Mar 20.
Shale gas is considered by many to have the potential to provide the UK with greater energy security, economic growth and jobs. However, development of a shale gas industry is highly contentious due to environmental concerns including the risk of groundwater pollution. Evidence suggests that the vertical separation between exploited shale units and aquifers is an important factor in the risk to groundwater from shale gas exploitation. A methodology is presented to assess the vertical separation between different pairs of aquifers and shales that are present across England and Wales. The application of the method is then demonstrated for two of these pairs-the Cretaceous Chalk Group aquifer and the Upper Jurassic Kimmeridge Clay Formation, and the Triassic sandstone aquifer and the Carboniferous Bowland Shale Formation. Challenges in defining what might be considered criteria for 'safe separation' between a shale gas formation and an overlying aquifer are discussed, in particular with respect to uncertainties in geological properties, aquifer extents and determination of socially acceptable risk levels. Modelled vertical separations suggest that the risk of aquifer contamination from shale exploration will vary greatly between shale-aquifer pairs and between regions and this will need to be considered carefully as part of the risk assessment and management for any shale gas development.
许多人认为页岩气有潜力为英国提供更高的能源安全、促进经济增长并创造就业机会。然而，由于包括地下水污染风险在内的环境问题，页岩气产业的发展极具争议性。有证据表明，被开采的页岩层与含水层之间的垂直间距是页岩气开采对地下水构成风险的一个重要因素。本文提出了一种方法，用于评估英格兰和威尔士各地不同含水层与页岩对之间的垂直间距。然后针对其中两对——白垩纪白垩群含水层和上侏罗统基默里奇黏土地层，以及三叠纪砂岩含水层和石炭纪鲍兰页岩地层，演示了该方法的应用。讨论了在确定页岩气层与上覆含水层之间“安全间距”标准时所面临的挑战，特别是地质特性、含水层范围的不确定性以及社会可接受风险水平的确定方面。模拟的垂直间距表明，页岩勘探对含水层造成污染的风险在不同的页岩 - 含水层对之间以及不同地区之间会有很大差异，在任何页岩气开发的风险评估和管理中，都需要仔细考虑这一点。
