title: Assessing Connectivity Between an Overlying Aquifer and a Coal Seam Gas Resource Using Methane Isotopes, Dissolved Organic Carbon and Tritium.
abstract: 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.
authors.affiliation: Connected Water Initiative Research Centre, UNSW Australia, UNSW Sydney, NSW, 2052, Australia.
authors.forename: Charlotte P
authors.initials: CP
authors.lastname: Iverach
authors.affiliation: 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.
authors.forename: Dioni I
authors.initials: DI
authors.lastname: Cendón
authors.affiliation: Australian Nuclear Science and Technology Organisation, New Illawarra Rd, Lucas Heights, NSW, 2234, Australia.
authors.forename: Stuart I
authors.initials: SI
authors.lastname: Hankin
authors.affiliation: Royal Holloway, University of London, Egham Hill, Egham, Surrey TW20 0EX, United Kingdom.
authors.forename: David
authors.initials: D
authors.lastname: Lowry
authors.affiliation: Royal Holloway, University of London, Egham Hill, Egham, Surrey TW20 0EX, United Kingdom.
authors.forename: Rebecca E
authors.initials: RE
authors.lastname: Fisher
authors.affiliation: School of Environmental Sciences, University of East Anglia, Norwich, Norfolk, NR4 7TJ, United Kingdom.
authors.forename: James L
authors.initials: JL
authors.lastname: France
authors.affiliation: Royal Holloway, University of London, Egham Hill, Egham, Surrey TW20 0EX, United Kingdom.
authors.forename: Euan G
authors.initials: EG
authors.lastname: Nisbet
authors.affiliation: Connected Water Initiative Research Centre, UNSW Australia, UNSW Sydney, NSW, 2052, Australia.
authors.forename: Andy
authors.initials: A
authors.lastname: Baker
authors.affiliation: Connected Water Initiative Research Centre, UNSW Australia, UNSW Sydney, NSW, 2052, Australia.
authors.forename: Bryce F J
authors.initials: BF
authors.lastname: Kelly