Potential groundwater impact from exploitation of shale gas in the UK
Stuart, M.E.. 2012 Potential groundwater impact from exploitation of shale gas in the UK. Nottingham, UK, British Geological Survey, 33pp. (OR/12/001) (Unpublished)Before downloading, please read NORA policies.
This report is a desk study to evaluate the potential risks to groundwater in the UK from exploitation of shale gas. As yet there is little information for UK so we need to look to the USA experience for transferable information. The UK may possess considerable reserves of shale gas. Significant areas include the Widmerpool Gulf, near Nottingham, and the Elsewick field near Blackpool. Work has begun near Blackpool. Hydraulic fracturing (“fracking”) in combination with horizontal drilling is an essential part of the shale gas production process and has been in use in the USA since about 1948. Extraction involved drilling of deep horizontal wells and enhancing the natural permeability of the shale by hydraulic fracturing. Fluid is introduced at a rate sufficient to raise the downhole pressure above the fracture pressure of the formation rock. The stress induced by the pressure creates fissures and interconnected cracks that increase the permeability of the formation and enable greater flow rates of gas into the well. Groundwater may be potentially contaminated by extraction of shale gas both from the constituents of shale gas itself, from the formulation and deep injection of water containing a cocktail of additives used for hydraulic fracturing and from flowback water released during gas extraction which may have a high content of saline formation water. Shale gas is predominantly methane of thermogenic origin with low percentages of C2 (ethane) and C3 (propane) hydrocarbons. Its 13C isotopic signature allows it to be distinguished from shallow biogenic methane in the subsurface. Documented instances of groundwater contamination from the USA are all related to the leakage of methane into groundwater. Fracking chemicals include hydrochloric acid, polyacrylamide, mineral oil, isopropanol, potassium chloride and ethylene glycol and low concentrations of pH buffers, corrosion inhibitors, biocides and gelling agents. The large volumes of water required may also put pressure on groundwater resources with impacts on other uses and groundwater dependent ecosystems. Reuse of flowback water involves treatment to remove high TDS. For UK we need to determine whether fields likely to be exploited for shale gas are overlain by significant aquifers. For aquifers at outcrop the vulnerability of groundwater to surface pollution from operations and flowback water can be informed by existing vulnerability mapping and other information. The vulnerability of groundwater to pollution from fracking operations and shale gas requires the determination of the relative depths of groundwater and shale gas reservoirs and the nature of the intervening strata.
|Item Type:||Report (UNSPECIFIED)|
|Programmes:||BGS Programmes 2010 > Groundwater Science|
|Additional Information:||This item has been internally reviewed but not externally peer-reviewed|
|Additional Keywords:||Groundwater, GroundwaterBGS, Groundwater protection|
|NORA Subject Terms:||Hydrology
|Date made live:||24 Jan 2012 16:53|
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