This project aimed to assess the potential of the Clare Sandstone, a saline aquifer in the Bando Trough and northern Murrurundi Trough, southern Gunnedah Basin, as a reservoir for sequestration of carbon dioxide emissions from coal-fired power generation. Reservoir characterisation of the unit, including determination of accurate storage volume, depends on thorough knowledge of its porosity and permeability, including petrographic analysis to delineate diagenetic influences. Framework grains are predominantly Lachlan Fold Belt sourced plutonic and metamorphic quartz, lithics and minor feldspar, with sporadic influences from New England Fold Belt volcanics. Kaolinite, illite and illite-smectite are the principal clays, which tend to inhibit porosity by blocking pore spaces and coating pore walls. Diagenetic history from textural relationships among cements indicates quartz overgrowths occurred first, followed by siderite, ankerite and calcite cement, then dawsonite (NaAlC₃(0H)₂) and finally, kaolinite. Dawsonite present in the Bando Trough, likely precipitated from permeating C0₂-rich fluids from nearby intrusive activity, and is useful as a natural analogue for geosequestration. SEM observations show the cements and diagenetic clays have acted to inhibit porosity and permeability by blocking pore throats. The study identifies the Clare Sandstone as a highly variable sedimentary unit with some potential as a geosequestration reservoir. More accurate determination of geosequestration capacity depends upon more detailed knowledge of the unit thickness, porosity, permeability, formation depth and salinity in the depocentre of the Murrurundi Trough.
37th Symposium on the Geology of the Sydney Basin. Proceedings of the 37th Symposium on the Geology of the Sydney Basin (Pokolbin, N.S.W. 6-7 May, 2010)