Deep Groundwater Circulation through Gas Shales in Mountain Belts

Abstract Thermal spring systems were examined in a mountainous region west of a major gas-shale development that occurs in the equivalent undeformed sedimentary basin. Geochemical data and geothermal modelling indicate that springs originate from circulation of surface water to depths exceeding 3.8 km. This implies that in the deformed belt surface waters actively circulate through gas-prone shales at depth. These circulation systems appear largely controlled by naturally occurring anomalous high permeability pathways that original by unusual tectonic features. Such pathways provide direct connection between deep gas-shale units and the shallow surface environment. This is observed by present day leakage of thermogenic gas and higher hydrocarbons to surface in spring waters. This leakage is partly attenuated by natural occurrence of methanotrophic microbial communities in the spring waters.