Iverach Charlotte P, Cendón Dioni I, Hankin Stuart I, Lowry David, Fisher Rebecca E, France James L, Nisbet Euan G, Baker Andy, Kelly Bryce F J
Connected Water Initiative Research Centre, UNSW Australia, UNSW Sydney, NSW, 2052, Australia.
Australian Nuclear Science and Technology Organisation, New Illawarra Rd, Lucas Heights, NSW, 2234, Australia.
Sci Rep. 2015 Nov 4;5:15996. doi: 10.1038/srep15996.
Coal seam gas (CSG) production can have an impact on groundwater quality and quantity in adjacent or overlying aquifers. To assess this impact we need to determine the background groundwater chemistry and to map geological pathways of hydraulic connectivity between aquifers. In south-east Queensland (Qld), Australia, a globally important CSG exploration and production province, we mapped hydraulic connectivity between the Walloon Coal Measures (WCM, the target formation for gas production) and the overlying Condamine River Alluvial Aquifer (CRAA), using groundwater methane (CH4) concentration and isotopic composition (δ(13)C-CH4), groundwater tritium ((3)H) and dissolved organic carbon (DOC) concentration. A continuous mobile CH4 survey adjacent to CSG developments was used to determine the source signature of CH4 derived from the WCM. Trends in groundwater δ(13)C-CH4 versus CH4 concentration, in association with DOC concentration and (3)H analysis, identify locations where CH4 in the groundwater of the CRAA most likely originates from the WCM. The methodology is widely applicable in unconventional gas development regions worldwide for providing an early indicator of geological pathways of hydraulic connectivity.
煤层气（CSG）的生产会对相邻或上覆含水层的地下水质量和水量产生影响。为评估这种影响，我们需要确定地下水的背景化学性质，并绘制含水层之间水力连通性的地质路径图。在澳大利亚昆士兰州东南部，这是一个在全球具有重要意义的煤层气勘探和生产省份，我们利用地下水甲烷（CH₄）浓度和同位素组成（δ¹³C-CH₄）、地下水氚（³H）以及溶解有机碳（DOC）浓度，绘制了瓦隆煤系（WCM，产气目标地层）与上覆的康达明河冲积含水层（CRAA）之间的水力连通性图。在煤层气开发区附近进行的连续移动CH₄调查，用于确定源自瓦隆煤系的CH₄的源特征。结合DOC浓度和³H分析，通过地下水δ¹³C-CH₄与CH₄浓度的变化趋势，确定了康达明河冲积含水层地下水中的CH₄最有可能源自瓦隆煤系的位置。该方法在全球非常规天然气开发区广泛适用，可为水力连通性的地质路径提供早期指示。
