Assessment of CO2 storage capability in Denison Trough, Bowen Basin

Abstract

The Bowen–Surat basin in eastern Queensland is a major centre of fossil energy production in Australia, producing 50% of Australia’s coal and 26% of Australia’s gas. Consequently, this region is also a major centre of carbon emissions. In 2018, fugitive emissions from the coal, oil and gas sectors were approximately 19.1 million tons of carbon dioxide (CO2) equivalent, which accounts for 11% of Queensland’s total emissions. The Denison Trough, (central Queensland) is the western depocentre of the Bowen Basin, an area of major natural gas supply for eastern Australia. Since the 1960s, 14 gas fields have been discovered and brought onto production. Denison Gas holds 10 petroleum leases across these discoveries, with a total acreage of 1159 km2. There are over 60 production wells, of which over 20 are depleted or close to depleted, and they provide potential target sites for carbon capture and storage (CCS). Preliminary analysis shows the depleted reservoir in the Aldebaran Sandstone at the Merivale Field (southern Denison Trough) could be the first candidate for CCS. The subsurface depth of the reservoir is 850–1200 m and could retain CO2 in the supercritical phase. The permeability varies from 1 to 2000 mD. As the reservoir pressure has been depleted, it is expected the injection operation at the depleted wells will be achievable. A simulation for estimating storage capacity was performed by Denison Gas. The results show the depleted gas reservoir has the capacity of storing up to 70 BCF (3600 kt) of CO2 in the future. This result encourages further work to determine seal integrity and economic feasibility.