Coal seam gas distribution and hydrodynamics of the Sydney Basin, NSW, Australia

Burra, A., Esterle, J. S. and Golding, S. D. (2014) Coal seam gas distribution and hydrodynamics of the Sydney Basin, NSW, Australia. Australian Journal of Earth Sciences, 61 3: 427-451. doi:10.1080/08120099.2014.912991


Author Burra, A.
Esterle, J. S.
Golding, S. D.
Title Coal seam gas distribution and hydrodynamics of the Sydney Basin, NSW, Australia
Journal name Australian Journal of Earth Sciences   Check publisher's open access policy
ISSN 1440-0952
0812-0099
Publication date 2014-01-01
Year available 2014
Sub-type Critical review of research, literature review, critical commentary
DOI 10.1080/08120099.2014.912991
Volume 61
Issue 3
Start page 427
End page 451
Total pages 25
Place of publication Abingdon, Oxfordshire, United Kingdom
Publisher Taylor and Francis
Language eng
Formatted abstract
This paper reviews various coal seam gas (CSG) models that have been developed for the Sydney Basin, and provides an alternative interpretation for gas composition layering and deep-seated CO2 origins. Open file CSG wells, supplemented by mine-scale information, were used to examine trends in gas content and composition at locations from the margin to the centre of the basin. Regionally available hydrochemistry data and interpretations of hydrodynamics were incorporated with conventional petroleum well data on porosity and permeability. The synthesised gas and groundwater model presented in this paper suggests that meteoric water flow under hydrostatic pressure transports methanogenic consortia into the subsurface and that water chemistry evolves during migration from calcium-rich freshwaters in inland recharge areas towards sodium-rich brackish water down-gradient and with depth. Groundwater chemistry changes result in the dissolution and precipitation of minerals as well as affecting the behaviour of dissolved gases such as CO2. Mixing of carbonate-rich waters with waters of significantly different chemistries at depth causes the liberation of CO2 gas from the solution that is adsorbed into the coal matrix in hydrodynamically closed terrains. In more open systems, excess CO2 in the groundwater (carried as bicarbonate) may lead to precipitation of calcite in the host strata. As a result, areas in the central and eastern parts of the basin do not host spatially extensive CO2 gas accumulations but experience more widespread calcite mineralisation, with gas compositions dominated by hydrocarbons, including wet gases. Basin boundary areas (commonly topographic and/or structural highs) in the northern, western and southern parts of the basin commonly contain CO2-rich gases at depth. This deep-seated CO2-rich gas is generally thought to derive from local to continental scale magmatic intrusions, but could also be the product of carbonate dissolution or acetate fermentation.
Keyword Sydney Basin
Coal seam gas
Gas origin
Hydrodynamics
Hydrochemistry
Co2
Carbonates
Q-Index Code C1
Q-Index Status Confirmed Code
Institutional Status UQ

Document type: Journal Article
Sub-type: Critical review of research, literature review, critical commentary
Collections: School of Earth Sciences Publications
Healthy Communities Research Centre Publications
Official 2015 Collection
 
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