Dampier Sub-basin Research Articles

Structural inheritance controls crustal-scale extensional fault-related folding in the Exmouth and Dampier Sub-basins, North West Shelf, Australia

Structural inheritance controls crustal-scale extensional fault-related folding in the Exmouth and Dampier Sub-basins, North West Shelf, Australia

Session 16. Oral Presentation for: Building a carbon storage portfolio for the Barrow and Dampier sub-basins – a national resource

Session 16. Oral Presentation for: Building a carbon storage portfolio for the Barrow and Dampier sub-basins – a national resource

Building a carbon storage portfolio for the Barrow and Dampier sub-basins – a national resource

The Australian government has recently legislated a 43% emissions reduction target for 2030 to drive net zero ambitions for 2050. The government plans for carbon capture and storage (CCS) to play a significant role in achieving this through greenhouse gas storage licence rounds. Rapid screening of Australia’s carbon storage opportunities is necessary to position future acreage release and ultimately identify and mature carbon storage sites. An industry collaboration between Geoscience Australia and SLB has conducted a basin-scale carbon storage assessment project for the Barrow and Dampier sub-basins. The project has built and modernised a subsurface database fit for CCS screening. The dataset was used as the foundation to create a carbon storage opportunity portfolio and storage resource assessment for the area. The project has three major streams: (1) CCS-focussed reprocessing, depth imaging and merging of 29 legacy seismic surveys covering 26,150 km2 – focussed on detailed image resolution for containment analysis. (2) A basin-wide audit of 1620 wells and databasing of available log data, 129 wells were carried through for petrophysical and rock physics analysis relevant to CCS. (3) A portfolio of carbon storage opportunities and associated capacity assessment for the Barrow–Dampier including saline aquifers and depleted fields ranked on storage capacity, reservoir and seal properties and integrity. The results of this study will be released via the National Offshore Petroleum Information Management System as a public resource to expedite CCS implementation for the region.

The spatio-temporal variation of exhumation and its impacts on the resource distribution in the Northern Carnarvon Basin, Australia

Deformation and rock fracture during exhumation can enhance rock porosity and permeability, thereby improving fluid migration through reservoirs and destroying seal integrity in caprocks. Therefore, analysing the spatio-temporal distribution of exhumation in connection to fluid migration models can be crucial for energy resource exploration and storage. Geological and geophysical evidence suggests that parts of the Northern Carnarvon Basin (NCB) were exhumed. However, the spatio-temporal distribution of this exhumation and its impacts on the region's resource distribution is yet to be established. We analysed porosity, sonic logs and paleotemperature data from 210 boreholes using compaction and vitrinite reflectance analysis techniques to constrain the spatio-temporal distribution of exhumation and its correlation to the region's resource distribution. We discovered that multiple exhumation phases occurred since the Late Triassic. The highest exhumation occurred in the Mid Jurassic, where approximately 1000 m of sediment thickness was eroded from the western and southwestern parts of the Exmouth Plateau. Exhumation at this time spatially correlates with magmatic intrusions in the NCB, and paleotemperature profiles indicate that sediments in the exhumed regions were partly heated by increased paleo-basal heat flow, suggesting that magmatic bodies through underplating and crustal intrusions were the primary causes of this exhumation. Another significant exhumation phase occurred in the Early Cretaceous, removing ∼800 m of sediments from the Exmouth, Barrow and Dampier Sub-basins. Depth-dependent extension events and magmatic intrusions possibly caused exhumation at this time. Significant exhumation ceased in the Early Cretaceous, and our study has established that the exhumation episodes in the NCB were part of large-scale regional events that affected the Australian Northwest Shelf. Combining results from different estimation techniques increased the spatio-temporal coverage of the analysis and improved the precision and accuracy of exhumation results.

Stratigraphic evolution and sediment dispersal in a marine rift-basin: The case of the Lewis trough, Eastern Dampier sub-basin (Australia)

The understanding of the stratigraphic evolution of marine rift basins is important for both “pure” scientific and economic reasons. From a hydrocarbon exploration point of view the main goal is to develop tools to predict reservoir location, quality, and extent. Stratigraphic models try to do that, and only historical cases can be used to test those models. On the other hand, depositional model cannot precisely predict reservoir location as factors unique to the specific basin under analysis affect sediment distribution (basin physiography, type of flows, among others). This aspect can be assessed only on a case-by-case basis and can be used for initial hypothesis generation based on analogues. This paper shows a case history study based on the integration of well logs, and 3D seismic data across the Eastern Dampier sub-basin, Northwester Shelf of Australia. Advanced seismic interpretation techniques, calibrated to well data, enable the definition of a chrono-stratigraphic framework of the late syn-rift sequence (Late Jurassic) of the Lewis Trough, and the description of the sediment distribution through the interpretation of geomorphological features. During the Late Jurassic three different channel systems deliver sandstones to the deep-water part of the basin through multiple entry points. The timing of the sediment input seems to be linked to variation of sediment input as during that time relative sea-level was slowly rising. The location of the entry points is related to local physiography and defies any attempt of prediction based on general “rules.” From a stratigraphic point view, the findings of the study support the idea that, in rift basin, mechanical subsidence is the primary control for accommodation space, with episodic pulses of extension followed by longer periods of tectonic quiescence. It is during these episodic movements along the basin's bounding faults that space for sedimentation is created. This interpretation is in striking contrast with the basic assumptions of the conventional sequence stratigraphy model.

Three-dimensional geometry and growth of a basement-involved fault network developed during multiphase extension, Enderby Terrace, North West Shelf of Australia

Abstract Basement fault reactivation, and the growth, interaction, and linkage with new fault segments are fundamentally three-dimensional and critical for understanding the evolution of fault network development in sedimentary basins. This paper analyzes the evolution of a complex, basement-involved extensional fault network on the Enderby Terrace on the eastern margin of the Dampier sub-basin, North West Shelf of Australia. A high-resolution, depth-converted, 3-D seismic reflection data volume is used to show that multiphase, oblique extensional reactivation of basement-involved faults controlled the development of the fault network in the overlying strata. Reactivation of the pre-existing faults initially led to the formation of overlying, en échelon Late Triassic–Middle Jurassic fault segments that, as WNW-directed rifting progressed on the margin, linked by breaching of relay zones to form two intersecting fault systems (F1 and F2–F4). Further reactivation in the latest Jurassic–Early Cretaceous (NNW-SSE extension) produced an additional set of en échelon fault arrays in the cover strata. The final fault network consists of main or principal faults and subordinate or splay faults, together with branch lines that link the various components. Our study shows that breaching of relay ramps and/or vertical linkages produces vertical and horizontal branch lines giving complex final fault geometries. We find that repeated activity of the basement-involved faults tends to form continuous and planar fault architectures that favor displacement transfer between the main constituent segments along strike and with depth.

Integration of new interpretation, attribute analysis and inversion results for the Dampier Sub-basin, North West Shelf of Australia

The Davros-Typhon Multi-Client 3D surveys are located approximately 70km from the north-west coast of Australia, largely covering the NE trending Dampier Sub-basin and straddling the Rankin Trend within the Northern Carnarvon Basin. The basins within the North West Shelf formed as a result of seafloor spreading, associated with the breakup of the North West margin of East Gondwana. The combined, contiguous Davros-Typhon survey areas cover a number of significant discoveries and producing fields, which include both oil and gas accumulations. The key objective of the survey was to enhance the imaging of Triassic to Lower Cretaceous reservoir units and to develop a new interpretation framework, made possible by the modern broadband acquisition parameters and advanced processing techniques. Challenges associated with imaging and interpretation include the effects of high velocity carbonate overburden, steeply dipping structures, fault shadow and structural complexity at depth, which is critical for evaluation of reservoir targets. A major reprocessing effort was undertaken to further mitigate these issues, which included Davros and a number of adjacent existing 3D surveys, resulting in the Typhon Multi-Client 3D. CGG Multi-client and New Ventures geoscientists, in collaboration with CGG Seismic Imaging, have undertaken new interpretation and amplitude versus offset (AVO) inversion analysis using subsets of the Typhon 3D. The resulting volume-based attribute analysis and integration of new AVO inversion results demonstrates enhanced attribute quality for the reprocessed data and provides a platform for quantitative analysis over a large area of the Northern Carnarvon Basin.

Multiphase activation of the boundary fault system of the eastern Dampier subbasin, Northwest Shelf of Australia

Investigating the timing, structural style, and development of multiphase extensional fault systems is essential for understanding rift basin evolution and for assessment of structural trap integrity. Borehole-controlled interpretation and analysis of two-dimensional and three-dimensional seismic data sets from the eastern Dampier subbasin indicate that a northeast-trending basement weakness zone was subjected to west-northwest–east-southeast oblique extension in the latest Triassic–late Middle Jurassic, resulting in systematic segmentation of the Rosemary fault system (RFS). Temporal stress change during Cretaceous north-south extension produced complex fault systems along the RFS, including (1) east-west–trending isolated faults with maximum displacement close to their center; (2) east-west–trending abutting faults, which initially nucleated as isolated faults, later abutted against the main structure, showing large displacement accruement on the composite fault; and (3) northeast-southwest–trending splay faults characterized by systematic left-stepping segmentation, with maximum displacement occurring at the point where the splay faults deviate from the main structure. In the Miocene, the RFS was locally reactivated by northwest-southeast compression in the northeastern part of the fault system, developing a compressive fault-propagation fold at the upper tip of the inverted extensional fault. This study suggests that the style of basin boundary fault reactivation depends largely on preexisting structures and temporal stress changes. The fault reactivation style is also a significant factor in influencing basin architecture, sediment distribution, fault linkage processes, and petroleum basin prospectivity.

3D structure and evolution of an extensional fault network of the eastern Dampier Sub-basin, North West Shelf of Australia

Insights of spatial and temporal development of fault network in 3D is crucial for understanding the process evolution of complex fault network and for evaluating the regional and local stresses control on structure development. We demonstrate a fault network on the eastern Dampier Sub-basin, North West Shelf of Australia, which consists of (1) a ENE-trending fault array that has a through-going segment at depth and a series of left-stepping fault splays at upper levels, and (2) a network of ENE- and NNE-trending intersecting faults decoupled from the basement structures. This research shows that the segmented ENE-trending fault array developed through three extensional phases in the Late Paleozoic, in the Early Jurassic, and in the Late Middle Jurassic. Fault analysis shows that the summed displacement of the segmented, en échelon faults behaves as a single fault and that the basement fault controlled the fault array in the upper section through vertical linkages– a typical coherent fault system. The NNE- and ENE-trending intersecting faults formed simultaneously in the Late Middle Jurassic; as such, they might have controlled by 3D strain field released from the Rosemary and Mermaid fault systems bounding the fault network. This implies that fault geometry derived from 3D seismic interpretation need to be treated with caution as the alignment of fault sets may not directly relate to regional, far-field stress but, in some cases, significantly modified by local stresses induced by reactivated larger faults. This study provides an analogue for the interpretation of other rift systems, where structures were controlled by competing forces of regional and local stresses and where reactivated and newly-formed structures coexist in polyphase of extensions.

Tectono-stratigraphy of the Dampier Sub-basin, North West Shelf of Australia

Abstract The Dampier Sub-basin, an inboard rift system of the Northern Carnarvon Basin in the North West Shelf, Australia, underwent two major phases of continental rifting in the Late Paleozoic and in the Latest Triassic to Late Jurassic. Six tectono-stratigraphic megasequences separated by regional unconformities have been identified: (1) Pre-Late Carboniferous Pre-rift 1; (2) Late Carboniferous to Late Permian Syn-rift 1; (3) Early to Latest Triassic Post-rift 1; (4) Latest Triassic to Early Late Jurassic Syn-rift 2; (5) Late Jurassic to Early Cretaceous Post-rift 2; and (6) Early Cretaceous to Present-day passive margin megasequences. The Late Paleozoic rifting produced a series of planar extensional faults on the eastern flank, some of which were later rotated by the Latest Triassic to Late Jurassic WNW–ESE extension to low-angles ( c. 30°). This Mesozoic extension was localized above a NE–SW-trending basement structure, resulting in en échelon inboard rift basins and overlapping boundary fault systems. The study outlines an updated basin tectono-stratigraphic model for the Dampier Sub-basin and provides new insights for structural evolution associated with the development of the North West Shelf passive continental margin of Australia.

Molecular fingerprint from plant biomarkers in Triassic-Jurassic petroleum source rocks from the Dampier sub-Basin, Northwest Shelf of Australia

Abstract Distinctive land plant biomarker distributions have been described for Triassic-Jurassic source rocks in the Dampier sub-Basin, Northwest Shelf of Australia. Proxies like the higher plant parameter [HPP = retene/(cadalene + retene)] cannot be applied to describe palaeoclimate globally; in fact, the HPP showed similar values (∼0.8) for Triassic and Jurassic source rocks despite the difference in sea level. The higher plant fingerprint [HPF or relative distribution of retene, cadalene and 6-isopropyl-1-isohexyl-2-methylnaphthalene (ip-iHMN)], however, represents a potential discrimination tool for source rock intervals. Here, we name this proxy as plant fingerprint (PF) since our investigation supports a non-vascular plant origin for ip-iHMN. The most distinctive patterns in the PF are found in the Early Jurassic with a predominance of cadalene (∼65%) in an arid climate, and the Middle Jurassic with a predominance of retene (∼70%) during a climate recovery under more humid conditions. Petroleum fluids from the Dampier sub-Basin are cadalene-dominated compared to fluids from the Barrow sub-Basin, which are retene-dominated. We emphasise that the present approach has only local implications and the parameters used herein (including the higher plant parameter or HPP) cannot lead to interpretations at a global scale.

Marginal fault systems of the Northern Carnarvon Basin: Evidence for multiple Palaeozoic extension events, North-West Shelf, Australia

Palaeozoic structures along the North-West margin of Australia have long been recognised as fundamental events responsible for the formation of the offshore basins that comprise this prolific hydrocarbon producing region. However, the tectonic setting in which this rifting occurred remains unclear. Detailed mapping of the geometry and tectono-stratigraphy of Permian and Carboniferous structures of the inboard Barrow, Dampier and Beagle sub-basins of the Northern Carnarvon Basin is possible using regional scale interpretation of publicly available 2D and 3D seismic data. Through seismic interpretation and mapping, we show two distinct orientations of structures that provide evidence for a poly-phase rift history of the North-West margin during the Palaeozoic. NNE trending faults of the Candace Terrace (Barrow sub-basin) were initiated in the Carboniferous or Devonian but were underfilled, resulting in erosion of the fault block crest and filling of the remnant rift-related topography by conformable sequences of later Permian and Triassic sediments. By contrast, NE-SW oriented faults of the Mermaid Nose (Dampier sub-basin) experienced a distinct phase of Permian activity and are unconformably overlain by Triassic sediments. In the Beagle sub-basin, both orientations of structures are present. Throughout the marginal fault systems of the Northern Carnarvon Basin, complex fault geometries and significant deformation of hanging wall strata are associated with reactivation of the eroded fault block crests and overprinting of faults during subsequent Mesozoic extension. This has implications for understanding the geodynamic evolution of a poly-phase extensional continental margin.

Normal fault linkage and reactivation, Dampier Sub-basin, Western Australia

The Northern Carnarvon Basin of Western Australia has experienced a polyphase deformation history during the breakup of Gondwana. Extension during the Carboniferous–Permian and a subsequent Early Jurassic rift event imposed two distinct fault systems, separated by a several kilometre-thick Triassic sedimentary sequence. Inboard areas, where Triassic sequences are thinner, Jurassic faults both detach above and also penetrate into Permian sequences. Other large-scale faults demonstrate a vertical hard/soft linkage between the two fault systems. In outboard areas where the Triassic is thicker, the relationship is less clear owing to the lower resolution of Permian sequences in seismic data. Here we undertake fault displacement analysis on three faults on the southern margin of the Exmouth Plateau to investigate the growth mechanism of Jurassic-aged faults and possible structural influence of deeper Permian faults. We find evidence of low-throw faults restricted to Mesozoic strata as more complex-segmented faults that have nucleated at a depth below that resolvable on seismic data. When considered in a regional context, the nature of faults in this study suggest oblique reactivation of the NE-trending Permian fabric, under east–west-oriented extension.

The significance of benzo[b]naphtho[d]furans in fluids and source rocks: New indicators of facies type in fluvial-deltaic systems

The distributions of benzo[b]naphtho[d]furans (BNFs) in source rocks and fluids (crude oil and condensate) are shown to be useful indicators of facies type in fluvial-deltaic systems from the Dampier sub-Basin, North West Shelf of Australia. The stratigraphy in the Dampier sub-Basin represents a challenging petroleum system where the organic matter is very similar in most of the Triassic-Jurassic sequences. These sections consist of a fluvial-deltaic system with increasing marine influence towards the end of the Jurassic period. Potential applications of BNFs for source rock characterisation as well as fluid – source rock correlations are reported for the first time. The formation of [1,2]BNF seems to be influenced by clay catalysis, and the ratio [2,1]/[1,2]BNF can be used to describe lithofacies. This ratio is much lower in sediments from fluvial-deltaic systems compared to clay-depleted sediments from marine environments (e.g. carbonate sequences). For this study, the Triassic source rocks show ratios of 0.9–1.5 with 25% w/w of clay content in the rock whereas the ratios for the Middle Jurassic source rocks are around 1.6–2.1 with 14% w/w of clay content. The BNF ratio is lowest in the Late Jurassic samples (0.8) with 28% w/w of clay minerals. The ternary plot of [2,1]-[1,2]-[2,3] BNFs could be applied to fluid–fluid and fluid-source rock correlations. However, further work needs to be done on the factors controlling the abundance of the [2,3]BNF which is more abundant in source rocks compared to the fluids generated and expelled from these.

δ13C of polycyclic aromatic hydrocarbons to establish the facies variations in a fluvial deltaic Triassic record (Dampier sub-Basin, Western Australia)

The δ13C of polycyclic aromatic hydrocarbons (PAHs) was measured in a series of Triassic and Jurassic source rocks from the Dampier sub-Basin, Carnarvon Basin, North West Shelf of Australia. These sequences correspond to fluvial deltaic systems which integrate the Mungaroo, Brigadier and Legendre Formations, and the organic matter has been assigned as mixed terrigenous/marine material. The relative abundance of the PAHs was plotted against the difference between δ13C values of 1,3,6,7-tetramethylnaphthalene (TeMN) and each PAH. We demonstrated here that samples plotting below 0 for Δ13C (Combustion Marker-1,3,6,7 TeMN) are related to delta-plain/front-deltaic facies or coaly fluvial deltaic facies (e.g. samples from the Mungaroo Formation - North Rankin-5, Goodwyn-9 and Goodwyn-5 wells) whereas the positive region for Δ13C (Combustion Marker-1,3,6,7 TeMN) is assigned to transitional facies deposited under an estuarine/lagoonal environment with a high sapropelic contribution (Brigadier Formation) and marginal marine environment (Legendre Formation). A similar separation for the samples was obtained with phenanthrene and other PAHs. The δ13C of PAHs in combination with their distributions can be used to establish the facies type i.e. delta-plain/front-deltaic from estuarine/lagoonal in a dominantly fluvial deltaic record. Our research provides new tools to take into account for further applications in fluid-source rock correlation studies which represent the main challenge in assessing petroleum systems in the sub-Basin.

The 2017 offshore acreage release areas: petroleum geological overview

In 2017, 21 new offshore petroleum exploration areas have been released. The majority of the areas are located along the North West Shelf spanning the Westralian Superbasin from the Bonaparte Basin in the north-east to the Northern Carnarvon Basin in the south-west. New areas have been released in offshore south-eastern Australia with new opportunities provided in the Otway, Bass and Gippsland basins. Two large areas in the northern Perth Basin, an offshore frontier, complete the 2017 Acreage Release. All Release Areas are supported by industry nominations and one new cash bid area has been offered in the Dampier Sub-basin. Geoscience Australia continues to support industry activities by acquiring, interpreting and integrating pre-competitive datasets that are made freely available as part of the agency’s regional petroleum geological studies. A new regional 2D seismic survey was acquired in the Houtman Sub-basin of the Perth Basin, forming the basis of the latest prospectivity study carried out by Geoscience Australia. The results of the study are presented in the technical program of the 2017 APPEA conference. A wealth of seismic and well data, submitted under the Offshore Petroleum and Greenhouse Gas Storage Act 2006 (OPGSSA) are made available through the National Offshore Petroleum Information Management System (NOPIMS). Additional datasets are accessible through Geoscience Australia’s data repository.

Extending interpretations of natural fractures from the wellbore using 3D attributes: The Carnarvon Basin, Australia

Natural fractures can be identified in wellbores using electric resistivity image logs; however, the challenge of predicting fracture orientations, densities, and probable contribution to subsurface fluid flow away from the wellbore remains. Regional interpretations of fracture sets are generally confined to areas featuring an extensive reservoir analog outcrop. We have made use of extensive data sets available in Western Australia’s Northern Carnarvon Basin to map subsurface natural fractures, contributing to a regional understanding of fracture sets that can be applied to broader parts of the basin. The Northern Carnarvon Basin is composed of distinct structural domains that have experienced differing tectonic histories. Interpretation of regional fractures was achieved through an integrated approach, incorporating electric resistivity image logs from 52 Carnarvon Basin wells and seismic attribute analysis of two 3D seismic data sets: Bonaventure_3D ([Formula: see text]) and HC_93_3D ([Formula: see text]). Integration of these two data sets allows for a regionally extensive identification of natural fractures away from well control. Fractures of differing age and character are identified within the basin: Outboard areas are dominated by fractures likely to be open to fluid flow that are parallel to subparallel to the approximately east–west present-day maximum horizontal stress, providing possible flow conduits between potential damage zones identified alongside the north–northeast/south–southwest-striking faults that constitute the major structural trend of the basin, and inboard areas dominated by northeast–southwest to north–northeast/south–southeast fractures formed in fault damage-zones alongside normal, and inverted-normal, faults at those orientations. Finally, fractures observed in wells from the Rankin Platform and Dampier Subbasin occur at neither of these orientations; rather, they closely parallel the strikes of local faults. Additionally, variation is seen in fracture strikes due to isotropic present-day stress magnitudes. This methodology extends fracture interpretations from the wellbore and throughout the region of interest, constituting a regional understanding of fracture sets that can be applied to broader parts of the basin.

Mesozoic rift onset and its impact on the sequence stratigraphic architecture of the Northern Carnarvon Basin

Ages varying from Late Triassic to Early Jurassic have been proposed by different authors for the onset of rifting in the Northern Carnarvon Basin. Seismic sections from the Exmouth Sub-basin and outer Exmouth Plateau demonstrate significant growth strata associated with displacement on normal faults starting at least at the base of the R. rhaetica zone (Rhaetian). This tectonic event coincides with a marked change in sequence architecture and a large landward shift (~300 km) of the paleo-shoreline to the vicinity of the Rankin and Alpha Arch trends. Rapid creation of accommodation in the inboard narrow rift basins (Exmouth, Barrow and Dampier sub-basins) is suggested to be the most likely cause of this major transgression. The preferential development of associated carbonate build-ups during the Rhaetian on the footwall side of active tilted fault blocks provides additional evidence for the onset of significant extensional faulting occurring during this time. An earlier more subtle initiation phase of rifting, however, is interpreted during the Norian, from around the middle part of the H. balmei biozone time, above which a change in stratigraphic architecture from aggrading to retrograding occurs. The observed structural and stratigraphic transitions can be related to typical phases of evolution described in many rift basins around the world. The work highlights the importance of integrating regional structural geology, sequence stratigraphy and depositional systems observations to provide robust constraints for basin evolutions.

Variation of natural fracture orientations in the Carnarvon Basin’s Rankin Platform and Dampier Sub-Basin, NWS, Western Australia

SUMMARY Natural fractures in the Carnarvon Basin’s Rankin Platform and Dampier Sub-Basin are identified using electrical resistivity image logs from 10 petroleum wells. In-situ stresses are diagnosed for the area using data from these and four additional wells, with these results indicating it likely that this study area hosts a relatively isotropic in-situ stress field. Identified fractures occur at all orientations, and demonstrate no dominant trend. They do not reflect the insitu stresses, nor the dominant north-northeast to northeast fault strikes. Rather, they most closely reflect the orientation of more local structures which the wells are adjacent to, demonstrating that natural fracture populations may be more dependent on local structure than dominant regional trends.

Fault linkage and reactivation on the northern margin of the Dampier sub-basin

SUMMARY The north-west margin of the Dampier sub-basin is characterised by a strongly segmented fault pattern. NE trending faults define the edge of the Rankin Platform, and separate it from the Kendrew Trough. However a secondary set of NNE trending faults define smaller scale graben on the edge of the Rankin Platform that preserve Lower and Middle Jurassic sediments. This strongly suggests oblique reactivation of an inherited NE trending basement fabric under WNW oriented extension during Middle Jurassic extension.