Gippsland Basin Research Articles

Developing a probabilistic compaction model for the Northern Carnarvon Basin using Bayesian inference

AbstractExhumation affects sedimentary basin evolution by influencing structural, pressure and temperature dynamics, thereby impacting energy resource formation. Compaction‐based methods are widely used to quantify exhumation, utilising sonic and porosity data to track sediment uplift from its maximum burial depths. However, uncertainties arise from applying empirical compaction models developed for specific geological regions, highlighting the need for region‐specific models. Even such region‐specific models contain uncertainties, which can compromise exhumation estimates. We, therefore, develop a probabilistic compaction model for the Northwest Shelf Basins using sonic data from normally compacted and unexhumed shales from the Northern Carnarvon Basin (NCB). The model's robustness is estimated using MCMC, and uncertainty propagation analysis is employed to assess the impact of model uncertainty on the model's predictive applications. The model shows exponential porosity reduction with depth, demonstrating rapid compaction from the surface to ca. 2 km and slower compaction thereafter. The model is then applied to interpret new datasets from the Canning, Gippsland and NCB regions. The results reveal that while some parts of the NCB exhibit normal compaction without exhumation, others were significantly exhumed. Conversely, Canning and Gippsland Basin data indicate signs of significant exhumation, as suggested by previous studies, thereby confirming the model's effectiveness outside the Northwest Shelf. Since the model could not explain data from exhumed regions, we inferred new models incorporating “exhumation” parameters to interpret the complex compaction histories of these areas, and the best‐fitting models were selected using the Bayes Factor method. Uncertainty analysis revealed that the impacts of model uncertainty on exhumation estimates are consistent across wide depth ranges. Our findings highlight the need to refine compaction models for better predictive reliability and informed resource exploration in sedimentary basins.

Session 21. Oral Presentation for: Modelling CO2 storage in oil and gas reservoirs in the Gippsland Basin

Session 21. Oral Presentation for: Modelling CO2 storage in oil and gas reservoirs in the Gippsland Basin

Session 20. Oral Presentation for: Planning for complex decommissioning projects in Australia – Gippsland Basin case study

Session 20. Oral Presentation for: Planning for complex decommissioning projects in Australia – Gippsland Basin case study

Session 10. Oral Presentation for: Insights into the depositional setting for the Gippsland Basin from modern basin-wide 3D datasets

Session 10. Oral Presentation for: Insights into the depositional setting for the Gippsland Basin from modern basin-wide 3D datasets

The Paleocene - Eocene mangroves of southeastern Australia: spatial and temporal occurrences across four geological basins

The advent of the Paleocene-Eocene Thermal Maximum (PETM), a ∼ 200 kyr period of global warming ca. 56 Ma, caused sea-levels to rise, transgressing near-coastal environments in southeastern (SE) Australia over >55,000 km2. During the PETM, warming tropical climates may have extended south to ≥60°S paleolatitude. The PETM in SE Australia is corroborated primarily by stable carbon isotope chemostratigraphy and detailed palynology records in four geological basins. Previous work showed that, in addition to the globally recognised carbon isotope excursion, the PETM interval in coastal SE Australia can be identified using the dual occurrence of the tropical mangrove Nypa palm pollen (Spinizonocolpites prominatus) accompanied by thermophilic marine dinoflagellate cysts (mainly Apectodinium hyperacanthum). We here document a total of twenty-six Gippsland Basin wells that record this Nypa-A.hyperacanthum association in the earliest Eocene Kingfish Formation (Lower Malvacipollis diversus Zone). In the Bass Basin, eight wells record Nypa-A.hyperacanthum association within the Eastern View Group basal Koorkah Formation, or lower part of the Lower M. diversus Zone (earliest Eocene). In the Bass Basin a further thirteen wells with Nypa occurrences near the top of the Cormorant Formation are found, which might be associated with the longer-term warmth of the Early Eocene Climatic Optimum (EECO, ∼53–49 Ma). Government bores and petroleum wells across the Otway Basin record the Nypa-A. hyperacanthum PETM association within the Pember Mudstone Lower M. diversus Zone in twenty-one bores. Nine horizons with Nypa occurrences occur within the Burrungule Member (EECO) at the top of the Dilwyn Formation. In western Tasmania, Nypa occurs in the Sorell Basin and Macquarie Harbour area within the Lower M. diversus Zone. Together, these observations show the remarkable extent of the mangrove-coasts that were established across the mid-high paleolatitudes in SE Australia during the warmest intervals of the Cenozoic, the PETM and EECO.

The ongoing transformational journey of Australia’s oldest and largest oil and gas operation

For over 50 years Gippsland Basin Joint Venture (GBJV) has been producing oil and gas from the Gippsland Basin. Through hard work, challenging the status quo and innovation, the business, the operation and the people have been on a transformational journey. You may have heard about our conventional expansion opportunities, Kipper-Tuna-Turrum development and Longford Gas Conditioning Plant, but have you heard about how GBJV is progressing carbon dioxide (CO2) to sales with BOC and Air Liquide or how the team has reduced flare by 46% since 2018? Have you heard how the team increased Longford’s capacity by 11% in 2022 to deliver the highest gas production since 2017 to meet market demand. Or about how we are transforming the operation through our Gippsland Asset Streamlining Project, where we will no longer have a Crude Stabilisation Plant or a Gas Plant 1 at Longford? We continue to focus on our reliable gas operation through upcoming projects such as Hastings Generation Project, and Kipper Compression Project while also pursuing meaningful reductions in greenhouse gas emissions such as South East Australia Carbon Capture and Storage Project in the Gippsland Basin. Our transformation to a ‘Modern Australian Gas Business’ has not only meant change for our facilities but also change for our people in how we work and the culture we have built. Every day, our teams work to supply essential energy to Australian homes and businesses while also being on a transformational journey to improve the sustainability of our operation and contribute to the energy transition.

Modelling CO2 storage in oil and gas reservoirs in the Gippsland Basin

The Gippsland Basin has world class geology for carbon capture and storage (CCS) and a long history of oil and gas production. Depleted oil and gas fields within the Gippsland Basin that are candidates for carbon dioxide (CO2) storage are in close proximity to existing infrastructure that could be repurposed as part of a CCS project. Modelling of CO2 storage in the depleted Bream oil and gas reservoir is being progressed. Bream reservoir properties are very well understood due to extensive geological and geophysical data sets available from wells and seismic data. Additionally, the field has been through three key phases of development during its production history; oil production and gas re-injection in 1988, gas cap blowdown started in 2002, and seasonal gas storage and withdrawal started in 2012 through to field shut-in in 2020. This provides a wealth of dynamic data that is used to calibrate the reservoir models to improve our confidence in the CO2 plume prediction. However, there are also challenges in modelling CO2 storage in depleted fields. Unlike saline aquifers, CO2 can be injected into a three-phase depleted reservoir that contains residual oil and gas saturation. The key aspects of our workflow to evaluate the plume behaviour are presented in this paper.

2023 Development and production review

Geopolitical uncertainty remained high in 2023 with Israeli actions in the Gaza strip, the continuing war in Ukraine and tension between China and several neighbouring countries. However, global inflationary pressures, surprisingly, eased during the year, and the prospect of a global recession faded from where it had been in 2022. In Australia continued activism around climate change issues, has impacted project developments and sentiment in the industry remained subdued. This paper looks back at the oil and gas production and development activities in Australia in 2023 providing historical context and trying to understand future implications for the industry. Liquefied natural gas (LNG) production in Australia remained close to record high levels although, not without problems. Both the Scarborough/Pluto 2 LNG project and the Barossa project continued to have legal and approval hurdles resulting in suspension of some execution activities. Elsewhere other projects continued with their plans, including the Kipper field in the Gippsland Basin, the Crux project in the Browse Basin and the Walyering project in the Perth Basin which was brought online in September 2023. The domestic markets also continued to have unique issues with major concerns about gas supply in the East, stalled developments and failing supply in the Northern Territory, and a renewed ban on any exports (including to other states) of gas from Western Australia.

Insights into the depositional setting for the Gippsland Basin from modern basin-wide 3D datasets

The Gippsland Basin is a prolific hydrocarbon basin, with gas and oil initially discovered in the Barracouta (1965) and Kingfish (1967) fields. Historically the basin was covered with a patchwork of legacy 3D seismic surveys acquired from 1980 to mid-2000s, shot with old technology resulting in sub-optimal imaging of the subsurface. CGG reprocessed 10,190 km2 of legacy 3D data as part of their ReGeneration project in 2018 and in 2020 acquired 8751 km2 of long offset, deep tow and undershot seismic data. With these data sets, Woodside has been able to extract images of the regional depositional systems through the basin’s evolution. These observations range in scale from interpretation of individual channels and channel belts to the distribution of the major shoreface systems and marine fans.

Goldilocks dilemma: lower cost, more supply, reduced emissions, and reliable trading partner. What is the outlook for Australia getting the gas balance just right?

Australia’s east and west coast domestic gas markets are physically and geographically separated. Each Australian gas market has followed a different trajectory, with the west being defined by large liquefied natural gas (LNG) projects, a relatively small domestic market, and a long-standing domestic gas reservation that historically ensured the domestic market was oversupplied and prices remained low. The east coast market instead relied for decades on supply from the Cooper and Gippsland basins which only supplied the domestic market, with both now in decline. The establishment of LNG export capacity in Queensland connected the east coast market to international markets for the first time and was followed by bans and moratoriums on gas development in some jurisdictions. Notwithstanding their very different history, both markets now face potential domestic supply shortages within a decade, and both have experienced government intervention in the past 12 months. Government’s stated aims are to lower prices, ensure ongoing investment in supply, reduce emissions, and continue LNG exports. This paper examines forecast supply and demand, the impact of government intervention, net zero policies and the importance of maintaining Australia’s export reputation as a reliable supplier. Getting this balance just right will require a challenging ‘Goldilocks moment’, with serious consequences if we get it wrong.

Pioneering CCS in Australia – the CarbonNet journey

The CarbonNet Project (CarbonNet), a trailblazing Carbon Capture and Storage (CCS) initiative, is progressing through what has been a transformative 14-year journey. Situated in southeast Victoria, this project has evolved from an interesting concept into a multifaceted project that promises to contribute to decarbonisation via its carbon dioxide (CO2) transport and storage project. Established in 2009 and funded by both Australian and Victorian Governments, CarbonNet has been at the forefront of the CCS journey in Australia. Its primary objective is to establish a hub in the Latrobe Valley, where a diverse range of industries supply CO2 for transport through an underground pipeline to the project’s initial offshore storage site, known as Pelican, in the globally renowned Gippsland Basin. The CarbonNet journey has been marked by significant milestones, including legislative changes to accommodate its future storage goals. Knowledge sharing and regulatory engagement have also been an ongoing priority, facilitating a robust feedback loop to ensure alignment with contemporary environmental standards. Adapting to dynamic market conditions, the project is working to secure customers within the rapidly evolving CO2 market whilst seeking to create a robust business model. More recently CarbonNet has been observing the emergence of proposed offshore wind and onshore transmission projects in the Gippsland region. This explosive growth of new energy solutions within Gippsland has created challenges and opportunities for the project. Jane Burton will provide an insightful overview of CarbonNet’s remarkable evolution, highlighting the critical role it plays in the journey towards establishing a net-zero future.

Aligning stars: making LNG imports happen in Australia

We present the inputs and results of a discounted cash flow model which details the requirements for an import terminal to eventualise. The key requirement is high certainty cash flows from foundation users. This can be made possible through capacity booking which can be potentially underwritten by governments to ensure security of supply during peak winter months. The out-chartering of the floating storage and regasification unit (FSRU) to serve as a liquefied natural gas (LNG) carrier during the peak northern winter will provide an additional revenue source. We also analyse the legacy supply decline and various price setting mechanisms for the southern states which will soon turn net importers. We will describe the status of the four projects in the pipeline and identify milestones. We conclude that an import terminal provides an alternative proposition in the southern states considering the highly seasonal demand profile, the decline of Gippsland Basin production, and the relative inflexibility of coal seam gas. Further, FSRUs can be redeployed to other regions, which reduces stranded asset risk from pipeline expansions, given Australia’s net zero targets.

Planning for complex decommissioning projects in Australia – Gippsland Basin case study

Over more than 50 years, safe and successful installation projects have enabled progressive development and expansion of the Gippsland Basin Joint Venture off the coast of Victoria, Australia. This has resulted in a highly integrated network of 19 offshore platforms which are now starting to progressively reach the end of their productive life and detailed planning for the first phase of decommissioning projects has increased in intensity. Decommissioning of these assets is planned to take place in a number of campaigns. The Campaign 1 Decommissioning Project includes the removal of up to 13 platforms and is likely to be the largest single project of its kind in the World. Experience of similar decommissioning projects in Australia is very limited, resulting in unprecedented challenges across many aspects of this project. This requires creative, innovative and adaptable solutions to be developed to enable an efficient execution methodology. This paper will explore the strategies, challenges and successes involved with the early planning and development phase of the Gippsland Basin Joint Venture, Campaign 1 Decommissioning Project. Key insights, from contracting, to execution planning and stakeholder engagement will be discussed, promoting sharing across the industry and improving efficiency for future decommissioning projects in Australia.

Early Pliocene Ostracoda from the Jemmys Point Formation, Gippsland Basin, southeastern Australia: nearshore and offshore origins of biodiversity

Early Pliocene ostracod faunas of the Jemmys Point Formation, onshore Gippsland Basin, yield a rich and well-preserved marine ostracod fauna of mixed shallow marine and deep marine origins. The ostracod faunas evidence a marine continental shelf palaeoenvironment that, during the deposition of one stratigraphic interval, was influenced by a strong, persistent upwelling current. This upwelling current allowed the migration of deep-sea Ostracoda (Philoneptunus sp.) onto the continental shelf. The deeper marine aspect of this early Pliocene fauna, and of modern ostracod faunas from the Bass Strait region, evidence the adaptation of deep shelf taxonomic clades to shallow cool temperate shelf environments and highlights one unusual evolutionary mechanism that has contributed to modern Bass Strait shallow marine biodiversity. Four species are newly described: Neonesidea chapminuta sp. nov., Tasmanocypris salaputia sp. nov., Oculocytheropteron jemmyensis sp. nov., and Philoneptunus plutonis sp. nov. Abbey P. McDonald* [a.mcdonald@deakin.edu.au], School of Life and Environmental Sciences, Deakin University, Burwood, Victoria 3125, Australia; Elizabeth A. Weldon [l.weldon@deakin.edu.au], School of Life and Environmental Sciences and Deakin Marine Research and Innovation Centre, Deakin University, Burwood, Victoria 3125, Australia; Mark T. Warne [mark.warne@deakin.edu.au], School of Life and Environmental Sciences and Deakin Marine Research and Innovation Centre, Deakin University, Burwood, Victoria 3125, Australia, and Museums Victoria, GPO Box 666, Melbourne, Victoria 3001, Australia.

Transformation of dense shelf water cascade into turbidity currents: Insights from high-resolution geophysical datasets

Dense shelf water cascade (DSWC) is a common oceanographic phenomenon on many continental shelves. Previous studies indicate that the DSWC could shape seabed physiography and carry seawater, sediment, and organic carbon a long distance from the continental shelf to the basin floor. However, it remains enigmatic how these DSWC's interact with seabed geomorphology and travel long distances from the shallow to deep marine environments. In this study, we employed high-resolution multibeam bathymetry, 2D and 3D seismic reflection, core description, and sediment grain size data from the Gippsland Basin, southeast offshore Australia. The continental shelf of the central Gippsland Basin stores sediment supplied by the along-shelf transported DSWC. By calculating the sediment motion threshold, we demonstrate that the DSWC is capable of entraining sediment from, and forming dense bottom nepheloid layers above, the seabed. Seismic reflection data reveal that cyclic steps are common on the shelf and slope, indicating a downslope-transported, supercritical current-dominated environment. Core observation and grain size analyses reveal that coarse-grained, Ta-typed turbidites are the major facies, indicating the presence of high-intensity downslope-traversing turbidity currents. Thus, supercritical turbidity currents are the dominant sedimentary process in the central Gippsland Basin. We illuminate that DSWC can interact with pre-existing seabed bathymetry created by a buried submarine landslide, resuspending sediment and igniting downslope-transported turbidity currents. The presence of numerous cyclic steps indicates that the turbidity current can evolve into a supercritical regime upon ignition, leaving complex seabed geomorphology and allowing the forming currents to travel across the shelf and extend more than 80 km down the lower slope. As revealed by our literature review, we imply that the transformation of DSWC into turbidity currents should be a common sedimentary process on outer continental shelves globally, significantly sculpting the seabed morphology and facilitating sediment and other marine particles transportation from shallow to deep sea.

Distribution, occurrence and identification of dibenzofuran, benzo[b]naphthofurans and their alkyl derivatives in Gippsland Basin source rocks

Dibenzofuran, benzo[b]naphthofurans and a series of their alkylated isomers were identified in coal, coaly shale, and shale extracts from the Gippsland Basin (Victoria, Australia). The dibenzofuran series include C0-C4 dibenzofurans, and the benzo[b]naphthofuran series are composed of benzo[b]naphthofuran, methylbenzo[b]naphthofurans, and possible dimethylbenzo[b]naphthofurans. Seventeen C2 dibenzofurans isomers (including six new isomers) were tentatively identified in rock extracts from the Gippsland Basin. The distribution and contents of C0-C4 dibenzofurans are different for Eocene and Paleocene rocks, providing a source rock age diagnostic correlation tool. Biological origin is the main factor that controls the abundance and distribution of dibenzofuran, benzo[b]naphthofuran and their alkylated isomers, based on investigation of source-, environment- and maturity-derived parameters. Variations in the C1 dibenzofurans/dibenzofuran ratio and the benzo[b]naphtho[2,1-d]furan/benzo[b]naphtho[1,2-d]furan ratio may reflect local paleoclimate changes in the Gippsland Basin.

Pre-commercial baseline passive seismic monitoring around CarbonNet's Pelican Site in the offshore Gippsland Basin, Victoria—The first five years

We undertook the design, development, and operation of a two-scale high-performance seismic network in SE Victoria to establish a baseline for natural seismicity around CarbonNet's Pelican Site. This is particularly important for providing assurance of the safety of the CO2 storage space and discriminating between natural and induced seismicity. The new high-precision earthquake catalogue developed from this work demonstrates a significant improvement in monitoring passive seismicity; a 77% average increase in annual event detections relative to pre-2017, magnitude of completeness lowered from 1.2 to 0.7, a minimum detection magnitude of -0.5, and location errors of ≤ ∼1 km within the network. Using the new earthquake catalogue, we also discovered the hitherto unknown deepest seismogenic zone in Australia in the offshore Gippsland Basin, with event depths exceeding 25 km. The spatial distribution of earthquakes indicates no seismic activity within a ∼10 km radius around the Pelican Site, providing confidence in its selection for potential CCS development. Together with the spatial distribution of earthquakes, newly estimated and more robust earthquake magnitude-frequency parameters enable the discrimination of natural versus induced seismicity with greater confidence. Continuous monitoring is recommended to overcome the limitations of the short monitoring time window.

Reservoir quality of the Late Cretaceous Volador Formation of the Latrobe group, Gippsland Basin, Australia: Implications from integrated analytical techniques

Increasing demand for energy due to the populous Eastern Australia has driven oil and gas industries to find new sources of hydrocarbons as they are the primary energy suppliers. Intensive study has been done on the Volador Formation in the Gippsland Basin by means of core-based petrophysical, sedimentological, and petrographic analyses as well as well log-based interpretation and capillary pressure test. Five wells from Kipper, Basker and Tuna fields with available dataset were investigated in this study: Kipper-1, Basker-1, Basker-2, Basker-5 and Tuna-4. Overall, the formation has good reservoir quality based on the high porosity and permeability values obtained through core and well log petrophysical analyses. The formation made up of mostly moderate to coarse quartz grains that has experienced strong anti-compaction and is poorly cemented. Montmorillonite and illite clays are seen dispersed in the rock formation, with the minority being mixed clays. These clays and diagenetic features including kaolinite cement and quartz overgrowth that can lead to porosity reduction only have insignificant impact on the overall reservoir quality. In addition, capillary pressure data shows that most samples are found in the transition to good reservoir zones (<50% saturation). The results obtained from this study have shown that the Volador Formation in the Gippsland Basin is worth for hydrocarbon exploration.

The distribution of metal and petroleum-derived contaminants within sediments around oil and gas infrastructure in the Gippsland Basin, Australia

As oil and gas infrastructure comes to the end of its working life, a decommissioning decision must be made: should the infrastructure be abandoned in situ, repurposed, partially removed, or fully removed? Environmental contaminants around oil and gas infrastructure could influence these decisions because contaminants in sediments could degrade the value of the infrastructure as habitat, enter the seafood supply if the area is re-opened for commercial and/or recreational fishing, or be made biologically available as sediment is resuspended when the structures are moved. An initial risk hypothesis, however, may postulate that these concerns are only relevant if contaminant concentrations are above screening values that predict the possibility of environmental harm or contaminant bioaccumulation. To determine whether a substantive contaminants-based risk assessment is needed for infrastructure in the Gippsland Basin (South-eastern Australia), we measured the concentration of metals and polycyclic aromatic hydrocarbons (PAHs) in benthic sediments collected around eight platforms earmarked for decommissioning. The measurements were compared to preset screening values and to background contaminant concentrations in reference sites. Lead (Pb), zinc (Zn), PAHs and other contaminants were occasionally measured at concentrations that exceeded reference values, most often within 150 m of the platforms. The exceedance of a few screening values by contaminants at some platforms indicates that these platforms require further analysis to determine the contaminant risks associated with any decommissioning option.

Re-discovering the Gummy gas field – Gippsland Basin

Recent sub-surface studies of the Gummy Gas Field have resulted in a significant upgrade of its gas and liquids resource potential. Previous interpretations had ascribed little resource potential to the field. Shell drilled Gummy-1 in 1990, a Golden Beach (GB) Subgroup gas/liquids discovery in the eastern Gippsland Basin. The GB Subgroup was previously described as a stacked, grading to generally thin, isolated sandstone reservoir hosting limited gas volumes. In 2022, a new study integrated the interpretation of the CGG Gippsland Multi-Client 3D seismic survey dataset with a re-look at the reservoir characterisation, petrophysical properties and reservoir pressures and found that reservoir quality is better than previously thought. The improved reservoir quality is interpreted to be the result of depositional reworking, which also increases confidence that the sandstones are laterally extensive. Consideration of the impact of regional pressure depletion due to nearby production from the GBJV fields has improved the understanding of the hydrocarbon columns encountered at Gummy-1. Increased hydrocarbon column heights are interpreted, which are consistent with wireline log evaluation and regional saturation-height data. Confidence that the seal at Gummy is working as effectively or better than offset fields and reservoirs is high. The new interpretation has also significantly improved the exploration potential for underlying gas reservoirs within the middle and lower GB Subgroup. Gummy-1 reached a total depth of 3530 m MDRT in a gas sandstone reservoir with an interpreted main gas column up to 185 m. Potential exists for additional gas in reservoir quality sandstones to be discovered in deeper exploration targets – the Gummy Deep exploration prospect. Combined with the adjacent Manta Gas Field, this demonstrates the enhanced potential for future commercial development in the area.