Chemical variability of groundwater samples collected from a coal seam gas exploration well, Maramarua, New Zealand

WATER RESEARCH

卷:47

Article

Taulis, Mauricio¹  Milke, Mark² 

[1] Queensland Univ Technol, Sch Earth Environm & Biol Sci, Brisbane, Qld 4001, Australia

[2] Univ Canterbury, Dept Civil & Nat Resources Engn, Christchurch 1, New Zealand

关键词: Coal seam gas (CSG);    Coalbed methane (CBM);    Groundwater;    Waikato;    Hydrochemistry;    Geochemical modelling;   

DOI  :  10.1016/j.watres.2012.11.003

来源: Elsevier

【 摘 要 】

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 wellhead 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 degrees C is consistently implemented. (C) 2012 Elsevier Ltd. All rights reserved.

【 授权许可】

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