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Chemical variability of groundwater samples collected from a Coal Seam Gas exploration well, Maramarua, New Zealand

Taulis, Mauricio & Milke, Mark (2012) Chemical variability of groundwater samples collected from a Coal Seam Gas exploration well, Maramarua, New Zealand. Water Research, 47(3), pp. 1021-1034.

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Abstract

A pilot study has produced 31 groundwater samples from a coal seam gas (CSG) exploration well located in Maramarua, New Zealand. This paper describes sources of CSG water chemistry variations, and makes sampling and analytical recommendations to minimize these variations. The hydrochemical character of these samples is studied using factor analysis, geochemical modelling, and a sparging experiment. Factor analysis unveils carbon dioxide (CO2) degassing as the principal cause of sample variation (about 33%). Geochemical modelling corroborates these results and identifies minor precipitation of carbonate minerals with degassing. The sparging experiment confirms the effect of CO2 degassing by showing a steady rise in pH while maintaining constant alkalinity. Factor analysis correlates variations in the major ion composition (about 17%) to changes in the pumping regime and to aquifer chemistry variations due to cation exchange reactions with argillaceous minerals. An effective CSG water sampling program can be put into practice by measuring pH at the well head and alkalinity at the laboratory; these data can later be used to calculate the carbonate speciation at the time the sample was collected. In addition, TDS variations can be reduced considerably if a correct drying temperature of 180°C is consistently implemented.

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ID Code: 54771
Item Type: Journal Article
Keywords: Coal Seam Gas, Groundwater, Hydrochemistry, Factor Analysis, carbonate chemistry
DOI: 10.1016/j.watres.2012.11.003
ISSN: 0043-1354
Subjects: Australian and New Zealand Standard Research Classification > EARTH SCIENCES (040000) > GEOLOGY (040300) > Petroleum and Coal Geology (040309)
Australian and New Zealand Standard Research Classification > EARTH SCIENCES (040000) > PHYSICAL GEOGRAPHY AND ENVIRONMENTAL GEOSCIENCE (040600) > Hydrogeology (040603)
Australian and New Zealand Standard Research Classification > EARTH SCIENCES (040000) > OTHER EARTH SCIENCES (049900) > Earth Sciences not elsewhere classified (049999)
Divisions: Current > Schools > School of Earth, Environmental & Biological Sciences
Past > QUT Faculties & Divisions > Faculty of Science and Technology
Past > Institutes > Institute for Sustainable Resources
Deposited On: 15 Nov 2012 08:18
Last Modified: 13 Jun 2013 01:17

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