Increased exploration activity in Area A of the Timor Gap Zone of Cooperation between Australia and Indonesia (ZOCA) has created the need for revision of the existing stratigraphic framework of the region. A chronostratigraphic approach to the analysis of the Mesozoic and Cainozoic succession of Western ZOCA provides a framework for improved stratigraphic prediction. The framework is based on the identification of depositional sequences by the integration of seismic and well data. Genetically related depositional sequences have been grouped into seven 'megasequences' which reflect distinct stages in the tectonic development of the basin.The Mesozoic and Cainozoic succession in the Northern Bonaparte Basin was deposited in a marginal sag basin that was affected by Triassic to Lower Cretaceous extension related to continental separation along the northwest margin of Australia. Four stages are seen in the evolution of the basin since the end of the Permian. Relative tectonic quiescence during the Triassic preceded two cycles of extension related to continental separation during the Jurassic to Earliest Cretaceous. Continental separation was followed by the development of a Cretaceous/Tertiary passive margin and a subsequent phase of tectonism related to the Miocene/Pliocene collision of the Indo-Australian and Eurasian plates. A tentative correlation has been made between the megasequence framework of Western ZOCA and the geological succession exposed on Timor Island.The framework forms the basis for a system of common stratigraphic nomenclature for the Timor Gap. The model also assists in understanding the tectono-strati-graphic evolution of the basin and is a foundation for the development of new play concepts that will support continuing exploration activity in the area.

No abstract

Underground hydrogen storage (UHS) has the potential to overcome the infrastructure and safety challenges of large-scale hydrogen storage, support long-term supply security and decrease delivery costs through economies of scale. Depleted hydrocarbon reservoirs and saline aquifers are likely to be significant contributors to UHS capacity in Australia. The principles of subsurface hydrogen storage in porous reservoir rocks are based on experience from both natural gas and carbon dioxide storage projects. However, as field-scale testing is required to demonstrate and mature the technology, a pre-feasibility study of the potential for an early UHS demonstration at the Otway International Test Centre (OITC) has been undertaken. Pre-feasibility studies have shown that while the characterisation of the subsurface storage reservoir is the most important aspect of the site-selection process, above-ground factors, such as facilities design, the logistics of hydrogen supply and the regulatory environment, significantly affect project design. Existing technologies require only minor adaptation to provide the surface infrastructure for a UHS project, but the logistics of hydrogen supply may be a significant factor in the scope of a demonstration project.

No abstract

As part of the Victorian Gas Program, new geological modelling of the Cretaceous to recent deposits in the Port Campbell Embayment and the Mussel Platform was carried out to investigate fault seal and trap integrity. Structural characterisation of the Late Cretaceous to present-day sedimentary sequence highlights cross-cutting fault trends defining potential structural traps containing Waarre Formation reservoirs. The fault trends are primarily controlled by Cretaceous-Paleogene extension and are reactivated during the Paleogene. Seismic facies in the top seal suggest an N-S environmental shift from open-marine to proximal nearshore marine. The quantification of fault membrane seals suggests that while reservoir-on-reservoir juxtapositions may enable some degree of lateral flow, efficient trapping relying on juxtaposition seal against the Belfast or Skull Creek mudstones is widespread. Fault geomechanics suggests that NW-SE and E-W faults accommodated most of the extensional strain and could have been associated with increased vertical structural permeability; however, there are no leakage indicators to support widespread vertical migration. These results do not support previous assumptions that fault seal integrity and top seal bypass represent a critical and widespread issue within the nearshore Otway Basin.