Safe geological carbon dioxide storage (GCS) requires rocks with suitable injectivity, capacity and sealing properties to ensure secure long-term containment of injected CO2.
A regional understanding of the subsurface is essential to determine the potential for GCS of a basin and to select target sites. This is best addressed by integrating the basin’s tectono-stratigraphic evolution, its gross depositional environment, and its hydrodynamic, thermal and stress regimes.
A basin-scale GCS assessment for the Barrow-Dampier sub-basins was conducted by Geoscience Australia and SLB. The objective of the study is to high-grade geological intervals and sites for potential GCS and to understand potential storage capacity and key risk factors. Stratigraphic and structural mapping of key storage intervals was performed using the reprocessed seismic volume and well database associated with the project. Analysis of critically stressed faults was used to estimate the likelihood of reactivation based on the far-field regional stress field and fault mechanical properties. Pressure, temperature, porosity, permeability, and water geochemistry data has been screened for >500 wells for assessing the storage unit intervals and predicting the hydrodynamic regime. Calibrated 2D basin models provide information on the regional pressure-temperature regime, porosity/permeability distribution, and sealing effectiveness. Potentiometric surface maps for the aquifer systems inform the distribution of CO2 plume migration. Results of this integrated regional basin study are used to quantify the risk of identified storage containers and to map the chance of success for GCS at a regional scale. The project results are to be made publicly available in Mar 2024.

The Caswell Sub-basin, situated within the Browse Basin, constitutes one of Australia’s primary hydrocarbon producing regions, with notable gas-condensate producing fields include Ichthys and Prelude, alongside a number of undeveloped fields. Jurassic syn-rift sandstones are extensively distributed across the basin and serve as one of the major reservoirs. However, reservoir sequences are typically intensely faulted, meaning that compartmentalization is a major risk. Furthermore, syn-kinematic reservoir sequences exhibit heterogeneity in thickness and lithofacies, with some areas experiencing localised erosion on uplifted fault blocks (e.g. Bassett West-1). Hence, understanding the nature of subsurface structures and their tectono-stratigraphic framework is crucial for evaluating the reservoir characteristics in the context of field development and additional exploration activities.
This study, therefore, aims to evaluate the structural framework and tectonic evolution of the Caswell Sub-basin from the Mesozoic to the present-day. Seismic interpretation of Paleozoic and younger sequences was conducted using multiple 3D seismic dataset extending over Ichthys, Prelude, Lasseter, and Crown fields, with interpretation stratigraphically constrained by over 20 wells. Our study demonstrates distinct structural patterns corresponding to different stratigraphic levels; NNE-SSW trending Permian-Triassic horsts and grabens, NE-SW trending Early-Middle Jurassic normal faults, Early Cretaceous polygonal faults and N-E trending Cenozoic en-echelon normal faults. The reactivation of deep horsts and grabens is suggested from development patterns of shallower Jurassic faults which impacts distribution of syn-kinematic sediments . This study highlights the importance of evaluating the structural linkage from basement to cover sequences to achieve a comprehensive understanding of reservoirs and associated petroleum systems.

Hydrogen plays a pivotal role in the global energy transitions, which requires underground storage. So far salt cavern storage is the only proven technology. The Boree Salt in the Adavale Basin, which locates mostly at depths from 1 km to 2.5 km and is up to 550 m thickness, consists predominantly of halite and is suitable for hydrogen storage. However, there is no adequate mappings. In recent years, passive seismic data (ambient noise) have received much interest as a cost-effective solution for subsurface imaging. The main signal from passive data is surface waves (usually below 1 Hz). We examine the capability of surface waves for the Bore Salt body mapping. We consider parameters of seismic sensor spacing, the dominant frequencies of the surface waves, and data noise levels. We demonstrate that surface waves from ambient noise can map the Boree Salt bodies with a survey distance of ~40 km. Between frequencies of 0.12 Hz and 0.25 Hz, results from the latter have better resolution because of a shorter wavelength. Moving to higher frequencies of 0.5 Hz and 1 Hz, however the resolution becomes worse, because the depth sensitivity of surface waves moves to shallower part of the model with increasing frequencies, rendering them incapable of effectively probing the targeted depths. For S/N above 5, station spacing can be as large as 2 km without compromising the mapping quality. Therefore cost-effective and environmentally-friendly passive seismic data can be a good alternative to the traditional active-source data for deep salt body imaging.

Evaporite sequences and diapirs in sedimentary basins play an important role in the global energy transition, as 1) locations for energy storage in caverns within bedded and diapiric salt deposits; 2) potential CO2 storage sites related to diapirism; 3) increased heat flow for geothermal energy; 4) critical minerals associated with evaporites and diapirs, and 5) potential for natural hydrogen exploration. Evaporite basins have the potential to provide financially viable energy solutions beyond their petroleum systems focus to date, yet key aspects of evaporite basin characterization to enable the development of these technologies are limited.
The characterization of evaporite sequence geometries and heterogeneity for gas storage is key. Salt–sediment interaction (halokinesis) involves long-term syntectonic deformation and sedimentation. Exotic lithologies are often incorporated into diapiric bodies as macroscopic inclusions, producing complexities that are difficult to image with seismic data and could introduce heterogeneity that reduces the sealing properties of the salt. The study of outcrop analogues and the generation of synthetic seismic provides the opportunity to improve prediction of the subsurface. Within Australia, approximately 15 evaporite basins are identified, including those that can be used for exploration and storage (e.g. Amadeus, Officer, Polda, Canning) and research development (e.g. Flinders, Willouran, Gammon Ranges). This paper presents a review of energy systems related to evaporite sequences and salt-sediment interaction in sedimentary basins, outlines key research questions of relevance for the role of salt basins in the energy transition, and demonstrates the value that Australian outcrop analogs provide for improved subsurface evaluation.