2024 PESA WEBINAR SERIES: WA Carbon Dioxide Geological Storage Atlas (GSWA)

In May 2021, the Ministerial Taskforce on Climate Action identified CO2 sequestration as a key priority, leading GSWA to receive funding in July 2022 to develop a CO2 Storage Atlas for Western Australia. The atlas incorporates updated geological datasets and new interpretations to assess CO2 storage potential across the onshore and State waters of the Perth, Southern Carnarvon, Northern Carnarvon, Canning, and Officer Basins.

Key to this project is regional subsurface mapping, which involves interpreting seismic data collected by petroleum companies over the past 70 years. The interpretation workflow includes loading digital seismic (SEGY) and well (LAS) data into Kingdom software. Since most available seismic data is in two-way time, mapping is first conducted in time before converting it to depth using various techniques. Mappable horizons identified on seismic data are tied to formation boundaries penetrated by petroleum wells and drillholes with downhole velocity data. As a byproduct, this project also involves capturing and cleaning up velocity survey data from well reports.

Depth mapping for the Officer and Perth Basins has been completed, and interpretation work continues for the Canning, Northern, and Southern Carnarvon Basins. Key features noted in the Perth and Officer Basin maps regarding CO2 storage potential include fault location and density, reservoir formation depths and thickness, and, in the Officer Basin, the presence of salt bodies.

To support the regional assessment of reservoir quality for the CO2 Storage Atlas project, 8,070 well log LAS files were standardized into a uniform format using Python. This standardization ensures consistent depth references, mnemonics, units, coordinates, and well names, enabling AI-based analysis. Furthermore, routine core analysis (RCA) data has been quality-checked and reformatted to enhance accessibility.

A subset of petrophysical interpretations have been completed for the Perth and Canning Bains. Storage targets were identified using a shale volume cutoff of 30% and an effective porosity cutoff of 10%, revealing the Perth Basin’s sand-prone nature. Given the highly faulted nature of the Perth Basin, the impact of faulting was evaluated through the interpretation of apparent formation water salinity. Significant intervals of Archie-quality sand are present in most wells, allowing for accurate assessments of apparent water resistivity. Water salinity changes frequently in each well but does not follow normal shale dewatering trends. This implies that vertical heterogeneity is significant but lateral movement of water across faults is expected, most likely through sand-on-sand juxtaposition. This evaluation also highlights which formations act as competent and reliable seals.

In summary, the petrophysical interpretation indicates that the Perth Basin is highly sand-prone. While structural containers are likely to be small, the presence of reservoir heterogeneity will enhance unstructured containment.

All datasets and results are available for download from WAPIMS via the CO2 Storage Atlas tile.