Heidelberg 2015 – wissenschaftliches Programm

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UP: Fachverband Umweltphysik

UP 9: Applied Noble Gas Physics Part 2

UP 9.5: Vortrag

Donnerstag, 26. März 2015, 16:15–16:30, C/gHS

Environmental Tracer and helium measurements in the context of Coal Seam Gas exploration. — •Axel Suckow and Stanley D. Smith — CSIRO Land and Water Flagship, Gate 5, Waite Road, Urrbrae, SA 5064, Australia

The Surat Basin in Northeast Queensland, Australia is subject to massive exploration and development for coal-seam gas extraction. To extract the gases, reduction of hydrostatic pressure in the Walloon Coal Measures by up to 70bar is necessary. The impact of this groundwater de-pressurization on adjacent aquifers is unknown. Also the flow regime of the underlying Hutton Sandstone and Precipice Sandstone aquifers is not well understood. Environmental tracers (SF6, CFCs, tritium, helium, 87Sr/86Sr, 14C, 36Cl) were measured along two north-south transects in the Hutton Sandstone aquifer. Also helium pore water profiles were obtained in vertical profiles through two aquitards isolating the Walloon Coal measures from the underlying Hutton Sandstone and this from the underlying Precipice Sandstone. Results indicate that groundwater in the Hutton has very low flow velocities and 36Cl decreases to background values along a flow distance of less than 150km. Vertical profiles of terrigenic helium through the aquitard formations indicate very low vertical flow in these formations and the aquifer system seems to be dominated by diffusion processes. However, it remains an open question to what extent the 36Cl/Cl decrease can be attributed to aging or is dominated by diffusive inflow of dead Cl from adjacent aquitards. To further elucidate this flow system, samples for 81Kr are planned along these transects.

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