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The Use of Chemistry, Isotopes and Gases as Indicators of Deeper Circulating Groundwater in the Main Karoo Basin
Expanded Title:A major concern regarding shale gas development is that deep borehole drilling and the hydraulic fracturing process (or fracking) may create conduits through which deep-seated groundwater could migrate to shallow aquifers. If this deep groundwater is of poor quality, and if shale gas development does facilitate upward migration of deep waters, then it is possible that poor-quality deep groundwater may blend with shallow Karoo groundwater currently used for water supplies. In some areas, the deep groundwater may even issue at the surface via leaking shale gas boreholes should they lose their integrity. This concern is primarily a long-term one. The overall aims of the project were: (1) In selected areas in the Main Karoo Basin where shale gas exploration is envisaged, characterise shallow (cold) and deep (warm) groundwater by analysing the waters (borehole and spring) for chemistry including trace elements, heavy metals, rare earth elements, isotopes, radioactivity and, where possible dissolved gases (e.g. methane and helium). (2) Identify specific determinands (out of the above) that distinguish shallow from deep groundwater and whether specific areas associated with shallow water samples contain traces of deep groundwater. (3) For regulatory purposes, develop a list of determinands that should be analysed in both shallow and deep boreholes in future shale gas exploration and development areas. Of the 20 assessed sites, seven could be confidently classified as deep or warm groundwater, whilst eight could be confidently classified as shallow or cold groundwater. The remaining five sites were classified as mixed.This study set out to identify indicators of deep groundwater flow in the Main Karoo Basin. It was not possible to obtain groundwater samples from the deep-seated shales that are being considered for shale gas exploration and development because no suitable deep boreholes exist. Instead, samples from warm springs and two deep boreholes that pass through the shales were obtained as the best approximation of deep-seated groundwaters in the Karoo at this stage. Deep and shallow groundwaters were characterised and determinands were identified to differentiate these waters. While this project noted fairly consistent geochemical patterns throughout the vast area of the Karoo, it must be stressed that the analyses, conclusions and recommendations presented pertain to a relatively small sample number of water and gas samples derived from sources of unknown depths.
Date Published:01/05/2015
Document Type:Research Report
Document Keywords:Ground Water, Hydrology
Document Format:Report
Document File Type:pdf
Research Report Type:Standard
WRC Report No:2254/1/15
ISBN No:978-1-4312-0678-0
Authors:Murray R; Swana K; Miller J; Talma S; Tredoux G; Vengosh A; Darrah T
Project No:K5/2254
Originator:WRC
Organizations:Groundwater Africa; University of Stellenbosch; Duke University, Durham , United States of America; The Ohio State University, Columbus, United States of America
Document Size:11 855 KB
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