Abstract

Australia's coal-fired power plants produce about 70% of the nation's total installed electricity generation capacity and emit about 190 million t of CO2/yr, of which about 44 million t come from central and southeast Queensland. A multidisciplinary study has identified the onshore Bowen Basin as having potential for geological storage of CO2. Storage potential has been documented within a 295-km2 (113-mi2) area on the eastern flank of the Wunger Ridge using a simplified regional three-dimensional model and is based on estimating injection rates of 1.2 million t CO2/yr for 25 yr. Paleogeographic interpretations of the Showgrounds Sandstone reservoir in the targeted injection area indicate a dominantly meandering-channel system that grades downdip into a deltaic system. Seismic interpretation indicates a relatively unfaulted seal and reservoir section. The depth to the reservoir extends to 2700 m (8858 ft).

CO2 injection simulations indicate that at least one horizontal or two vertical wells would be required to inject at the proposed rate into homogeneous reservoirs with a thickness of approximately 5 m (16 ft) and permeability of 1 d. The existence of intrareservoir shale baffles necessitates additional wells to maintain the necessary injection rate; this is also true for medium-permeability reservoirs. The long-term storage of the injected CO2 involves either stratigraphic and residual gas trapping along a 10–15-km (6–9-mi) migration path and, ultimately, potentially, within updip depleted hydrocarbon fields or trapping in medium-permeability rocks. Trapping success will be a function of optimal reservoir characteristics and the distribution of seals and baffles. This optimization may target specific, as-yet to be determined, permeability ranges.

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