A TECHNICAL APPRAISAL OF STORAGE OF GORGON CO2 AT BARROW ISLAND, NORTH WEST SHELF

Abstract

The Gorgon gas field lies 70 km west of Barrow Island in 200 m of water. The field is jointly owned by ChevronTexaco Australia, Shell Development Australia and Mobil Exploration and Producing Australia and has certified proven hydrocarbon gas reserves of 272.69 Giga cubic metres (Gm3) (9.63 trillion cubic feet (Tcf)). Carbon dioxide (CO2) comprises about 14 mole % of the raw gas resource.

The Gorgon joint venture is committed to the responsible management of greenhouse gas emissions and this ongoing commitment is reflected in the plan to inject Gorgon CO2 into the Dupuy Formation beneath Barrow Island, unless it is cost prohibitive or technically unfeasible.

This paper summarises the Phase 1 assessment made by the Western Australian Department of Industry and Resources (DoIR) into the technical feasibility of the Gorgon CO2 storage project. Technical feasibility is defined as the ability to inject CO2 in a manner that has acceptable safety, environmental and reservoir risks based on assessments made by both the Gorgon joint venture and regulatory bodies.

DoIR and ChevronTexaco Australia agreed to regularly review the technical work for due diligence purposes. To assist in the assessment, DoIR engaged the services of Curtin University. The Phase 1 review was completed in June 2003 and provided technical assurance on the feasibility of CO2 storage beneath Barrow Island. This provided one of the criteria for the WA State Government’s decision to grant in-principle access to Barrow Island for the project.

The Phase 1 review provided a comparative risk analysis and recommendations related to improving the sub-surface definition of the earth model, further assessment of seal and fault integrity, injectivity, near-well bore reactions and CO2 surveillance and monitoring technologies. Key DoIR recommendations included the need for additional geological data and a long-term monitoring strategy for reservoir management and contingency planning. The second Phase of due diligence commenced in February 2004.