New insights into the stratigraphy of the Otway Basin

2020 ◽  
Vol 60 (2) ◽  
pp. 691
Author(s):  
Betina Bendall ◽  
Anne Forbes ◽  
Dan Revie ◽  
Rami Eid ◽  
Shannon Herley ◽  
...  
Keyword(s):  
South Australia ◽  
Petroleum Exploration ◽  
Hydrocarbon Production ◽  
Sedimentary Sequences ◽  
Structural Relationships ◽  
Geochemical Variation ◽  
Complex Structural ◽  
Geochemical Analyses ◽  
Stratigraphic Nomenclature ◽  
The Antarctic

The Otway Basin is one of the best known and most actively explored of a series of Mesozoic basins formed along the southern coastline of Australia by the rifting of the Antarctic and Australian plates during the Cretaceous. The basin offers a diversity of play types, with at least three major sedimentary sequences forming conventional targets for petroleum exploration in the onshore basin. The Penola Trough in South Australia has enjoyed over 20 years of commercial hydrocarbon production from the sandstones of the Early Cretaceous Otway Group comprising the Crayfish Subgroup (Pretty Hill Formation and Katnook sandstones) and Eumeralla Formation (Windermere Sandstone Member). Lithostratigraphic characterisation and nomenclature for these sequences are poorly constrained, challenging correlation across the border into the potentially petroleum prospective Victorian Penola Trough region. The Geological Survey of Victoria (GSV), as part of the Victorian Gas Program, commissioned Chemostrat Australia to undertake an 11-well chemostratigraphic study of the Victorian Otway Basin. The South Australia Department for Energy and Mining, GSV and Chemostrat Australia are working collaboratively to develop a consistent, basin-wide schema for the stratigraphic nomenclature of the Otway Basin within a chemostratigraphic framework. Variability in the mineralogy and hence inorganic geochemistry of sediments reflects changes in provenance, lithic composition, facies changes, weathering and diagenesis. This geochemical variation enables the differentiation of apparently uniform sedimentary successions into unique sequences and packages, aiding in the resolution of complex structural relationships and facies changes. In this paper, we present the preliminary results of detailed geochemical analyses and interpretation of 15 wells from across the Otway Basin and the potential impacts on hydrocarbon prospectivity.

Resolving lithostratigraphic complexities in the Crayfish Group, Otway Basin using chemostratigraphy

2021 ◽  
Vol 61 (2) ◽  
pp. 588
Author(s):  
Betina Bendall ◽  
Anne Forbes ◽  
Tony Hill
Keyword(s):  
Continental Margin ◽  
Structural Complexity ◽  
Significant Part ◽  
Rift System ◽  
Lacustrine Environment ◽  
Hydrocarbon Production ◽  
Inorganic Geochemistry ◽  
System A ◽  
Structural Relationships ◽  
Complex Structural

The Otway Basin comprises a significant part of the eastern Australian Southern Rift System, a divergent passive continental margin formed during the Cretaceous separation of the Australian and Antarctic continents. Early rifting activity resulted in the development of many half grabens within the Otway Basin, which are largely infilled by sediments of the Casterton Formation and Crayfish Group. Despite over 20 years of exploration and hydrocarbon production from these units however, their lithostratigraphic characterisation and nomenclature remain ambiguous, with structural complexity and prevalent lateral facies changes leading to confusion in their basin-wide correlation. Deposited in a largely non-marine, fluvial/lacustrine environment, repeating cycles of sandstones and shales of the Crayfish Group can be difficult to resolve using petrology, palynology and wireline log data. The use of chemostratigraphy is favoured as an investigative tool in this situation since changes in provenance, lithic composition, facies, weathering and diagenesis are reflected in the mineralogy of the sediments, resulting in variations in their inorganic geochemistry. Uniform sedimentary successions can thus potentially be differentiated into unique sequences and packages based on their characteristic geochemistry, aiding in the resolution of complex structural relationships and facies changes. In this study, we present new inorganic geochemistry data for four key wells in the South Australian (SA) Penola Trough and interpret the geochemistry data consistent with, and building on, the chemostratigraphic schema of Forbes et al. to demonstrate its utility and robustness. We then undertake inter-well wireline log correlations across the SA Penola Trough using the wells with chemostratigraphic data as controls.

New insights into the organic geochemistry of the Otway Basin

2020 ◽  
Vol 60 (2) ◽  
pp. 712
Author(s):  
Tony Hill ◽  
Betina Bendall ◽  
Andrew Murray
Keyword(s):  
Organic Geochemistry ◽  
South Australia ◽  
Hydrocarbon Production ◽  
Recent Success ◽  
Algal Organic Matter ◽  
Geochemical Analyses ◽  
Rock Eval ◽  
Lacustrine Facies ◽  
Low Sulfur ◽  
Paraffinic Oil

The Penola Trough of the Otway Basin in South Australia has enjoyed over 20 years of commercial hydrocarbon production from the sandstones of the Early Cretaceous Otway Group with 71.46 PJ sales gas and 65840 kL of condensate produced from five fields until production ceased in 2011. Recent success in Haselgrove 3, where a newly discovered deeper reservoir underlying depleted reservoirs of the Pretty Hill Formation flowed 25 MMscfd on test heralds a new phase of exploration and appraisal with a 2C Contingent Resource of 87 PJ assigned to the discovery. These hydrocarbons are considered to have been principally derived from lacustrine, floodplain and back swamp facies of the Pretty Hill Formation and lacustrine facies of the underlying Casterton Formation. The South Australia Department for Energy and Mining is currently investigating an unnamed Late Jurassic syn-rift sequence of interbedded metasediments, tuffaceous sediments and organically-rich shale, first identified as fractured basement in Sawpit 1, located on the northern flanks of the Penola Trough and which unconformably underlies the Casterton Formation. A low-sulfur medium-gravity paraffinic oil was recovered from drill stem tests from this well and subsequent total organic carbon and Rock-Eval analyses for the same unit in nearby Sawpit 2 identified a source rock containing algal organic matter and thought to be deposited in a deep anoxic lake setting. In this paper, we will present the preliminary results of detailed geochemical analyses of rocks and rock extracts from this previously unrecognised syn-rift sequence and discuss implications for hydrocarbon prospectivity in the deeper portions of the Penola Trough.

Origin of the secondary REE-minerals at the Paratoo copper deposit near Yunta, South Australia

2006 ◽  
Vol 70 (6) ◽  
pp. 609-627 ◽  
Author(s):  
J. Brugger ◽  
J. Ogierman ◽  
A. Pring ◽  
H. Waldron ◽  
U. Kolitsch
Keyword(s):  
Base Metal ◽  
South Australia ◽  
Copper Deposit ◽  
Rock Interaction ◽  
Widespread Occurrence ◽  
Fe Oxide ◽  
Left Behind ◽  
Copper Gold ◽  
Geochemical Analyses ◽  
Light Rare Earth Elements

AbstractThe Paratoo copper deposit, located in the Neoproterozoic to Cambrian Adelaide Geosyncline, South Australia, produced around 360 tons of Cu between 1888 and 1967 from oxidized ores. The deposit is located in the core of a breached, doubly plunging anticline, near a zone of disruption containing brecciated Adelaidean sedimentary rocks and dolerite (‘Paratoo Diapir’), and hosted in dolomitic shales of the Neoproterozoic Burra Formation. Near the surface, the mineralization resides mainly in deeply weathered quartz-magnetite-sulphide (pyrite, chalcopyrite) veins (⩽10 cm wide). At depth, drill cores reveal disseminated magnetite, pyrite, chalcopyrite, copper sulphide and native copper associated with extensive potassic alteration. K-Na-rich fluids also affected the dolerite in the ‘Paratoo diapir’, resulting in the precipitation of K-feldspar, dravite and K-bearing chabazite-Na. The most likely scenario for the genesis of the Paratoo deposit involves circulation of basinal fluids, focusing into the ‘Paratoo Diapir’, and ore precipitation through neutralization by fluid-rock interaction with the dolomitic shales hosting the mineralization.The Paratoo deposit is deeply weathered, with malachite and chrysocolla (± tenorite and cuprite) containing the bulk of the copper recovered from the shallow workings. A diverse assemblage of secondary REE-bearing carbonate minerals, including the new species decrespignyite-(Y) and paratooite-(La), is associated with the weathered base metal and magnetite ores. Whole-rock geochemical analyses of fresh and mineralized host rock and of vein material reveals that the mineralization is associated with a strong, albeit highly variable, enrichment in light rare earth elements (LREE). This association indicates that REE and base metals were introduced by the same hydrothermal fluid. The strong negative Ce anomaly found in secondary REE minerals and mineralized rock samples suggests an upgrade of the REE contents in the weathering zone, insoluble Ce4+ being left behind.The Fe-oxide-REE-base metal association at Paratoo is also characteristic of the giant Mesoproterozoic Fe oxide copper gold deposit of Olympic Dam, located 350 km to the NW. A similar association is found in the Palaeozoic deposits of the Mt Painter Inlier, 300 km to the NNE. The widespread occurrence of this elemental association in the Province probably reflects the geochemistry of the basement, which contains numerous Mesoproterozoic granites enriched in REE and U.

Records of vagrant fur seals (family Otariidae) in South Australia

2014 ◽  
Vol 36 (2) ◽  
pp. 154 ◽  
Author(s):  
Peter D. Shaughnessy ◽  
Catherine M. Kemper ◽  
David Stemmer ◽  
Jane McKenzie
Keyword(s):  
New Zealand ◽  
South Australia ◽  
The South ◽  
South Indian Ocean ◽  
Fur Seals ◽  
South Indian ◽  
Fur Seal ◽  
New Zealand Fur Seal ◽  
The Antarctic ◽  
Subantarctic Fur Seals

Two fur seal species breed on the southern coast of Australia: the Australian fur seal (Arctocephalus pusillus doriferus) and the New Zealand fur seal (A. forsteri). Two other species are vagrants: the subantarctic fur seal (A. tropicalis) and the Antarctic fur seal (A. gazella). We document records of vagrant fur seals in South Australia from 1982 to 2012 based primarily on records from the South Australian Museum. There were 86 subantarctic fur seals: 49 specimens and 37 sightings. Most (77%) were recorded from July to October and 83% of all records were juveniles. All but two specimens were collected between July and November. Sightings were prevalent during the same period, but there were also nine sightings during summer (December–February), several of healthy-looking adults. Notable concentrations were near Victor Harbor, on Kangaroo Island and Eyre Peninsula. Likely sources of subantarctic fur seals seen in South Australia are Macquarie and Amsterdam Islands in the South Indian Ocean, ~2700 km south-east and 5200 km west of SA, respectively. There were two sightings of Antarctic fur seals, both of adults, on Kangaroo Island at New Zealand fur seal breeding colonies. Records of this species for continental Australia and nearby islands are infrequent.

SELECTING THE WINNING BID

2002 ◽  
Vol 42 (1) ◽  
pp. 523
Author(s):  
E. Alexander ◽  
J. Morton
Keyword(s):  
Scoring System ◽  
Net Present Value ◽  
South Australia ◽  
Petroleum Exploration ◽  
3D Seismic ◽  
Management Philosophy ◽  
Work Program ◽  
Single Target ◽  
2D And 3D ◽  
Selection Of

Work program bidding is established as the favoured method of allocating petroleum exploration tenements in offshore Australian waters and most of onshore Australia. However, the selection of winning bids can be complicated by the ranking of 2D versus 3D seismic, seismic versus drilling, program timing issues etc. On occasion the selection of the winning bids has been contentious. This paper summarises the process developed by the Petroleum Group in South Australia to select the winning work program bids for prospective onshore blocks for which bids have been gazetted. No other Australian jurisdiction has yet publicly released their detailed bid assessment processes.Onshore acreage releases with work program bidding have been used in South Australia since the 1980s by Petroleum Group to:focus industry onto specific prospective areas of the State (e.g. the Cooper Basin post expiry of PELs 5 and 6 in 1999); maximise exploration commitments; and achieve competition policy.The South Australian Petroleum Act 2000 allows cash or work program bidding to be used depending on the acreage. Acreage releases are announced by Ministerial press release. Associated clear bid assessment criteria are published together with promotional material to aid applicants. The date and time for close of bidding are also established, usually allowing a 6–9 month acreage evaluation period, the timeframe depending on the volume of data involved, i.e. the exploration maturity of the area.Applications received as a result of a gazettal process (i.e. competing bids) are assessed by a process designed to ensure probity and to achieve the over-arching aim of the bidding process i.e. the suitability of the applicants proposed work program for evaluating the prospectivity of the licence area and discovering petroleum.A scoring system has been developed which establishes, for each bid what is effectively a risked net present value in well equivalents. In this system, guaranteed work scores higher than non-guaranteed work; early work scores higher than later work; wells with multiple targets are scored higher than single target wells; 2D and 3D seismic and other exploration activity is converted into well equivalents; and loading of the later, non-guaranteed years of work programs are heavily discounted.The scoring system may also take into account differences in the amount and density of exploration data and minor variations may be made to the system to take this into account. It is intended that details of the scoring system to be used in bid assessment will be published each time bids are sought to ensure transparency and a level playing field.Comparisons are made with acreage management philosophy and processes used by other regulatory regimes in Australia and internationally.

Review of the 2009 offshore petroleum exploration release areas

2009 ◽  
Vol 49 (1) ◽  
pp. 465
Author(s):  
Thomas Bernecker
Keyword(s):  
Deep Water ◽  
South Australia ◽  
Northern Territory ◽  
Data Availability ◽  
Petroleum Exploration ◽  
Release Date ◽  
North West ◽  
The North ◽  
Release Area ◽  
Block Sizes

The Australian Government formally releases new offshore exploration areas at the annual APPEA conference. This year, 31 areas plus two special areas in five offshore basins are being released for work program bidding. Closing dates for bid submissions are either six or twelve months after the release date (i.e. 3 December 2009 and 29 April 2010), depending on the exploration status in these areas is and on data availability. The 2009 release areas are located in Commonwealth waters offshore Northern Territory, Western Australia, South Australia and Victoria, comprising intensively explored areas close to existing production as well as new frontiers. As usual, the North West Shelf features very prominently and is complimented by new areas along the southern margin, including frontier exploration areas in the Ceduna Sub-basin (Bight Basin) and the Otway Basin. The Bonaparte Basin is represented by one release area in the Malita Graben, while five areas are available in the Southern Browse Basin in an under-explored area of the basin. A total of 14 areas are being released in the Carnarvon Basin, with eight areas located in the Dampier Sub-basin, three small blocks in the Rankin Platform and three large blocks on the Northern Exmouth Plateau (these are considered a deep water frontier). In the south, six large areas are on offer in the Ceduna Sub-basin and five areas of varying sizes are being released in the Otway Basin, including a deep water frontier offshore Victoria. The special release areas are located in the Petrel Sub-basin, Bonaparte Basin offshore Northern Territory, and encompass the Turtle/Barnett oil discoveries. The 2009 offshore acreage release offers a wide variety of block sizes in shallow as well as deep water environments. Area selection has been undertaken in consultation with industry, the states and Territory. This year’s acreage release caters for the whole gamut of exploration companies given that many areas are close to existing infrastructure while others are located in frontier offshore regions. As part of Geoscience Australia’s Offshore Energy Security Program, new data has been acquired in offshore frontier regions and have yielded encouraging insights into the hydrocarbon prospectivity of the Ceduna-Sub-basin.

ENVIRONMENTAL IMPACT OF SEISMIC OPERATIONS IN THE OTWAY BASIN, SOUTH AUSTRALIA

1994 ◽  
Vol 34 (1) ◽  
pp. 741 ◽  
Author(s):  
M. L. Williams ◽  
A. J. Boulton ◽  
M. Hyde ◽  
A. J. Kinnear ◽  
C. D. Cockshell
Keyword(s):  
Environmental Management ◽  
Environmental Impact ◽  
Vegetation Structure ◽  
South Australia ◽  
Petroleum Exploration ◽  
Seismic Exploration ◽  
Native Vegetation ◽  
Seismic Line ◽  
The Impact ◽  
Seismic Lines

The Department of Mines and Energy, South Australia (DME) contracted Michael Williams and Associates Pty Ltd to audit the environmental management of seismic exploration operations in the South Australian Otway Basin. The audit was carried out in early 1992 and covered petroleum exploration operators and DME environmental management systems. An innovative field sampling technique was developed to compare the environmental impact of two different seismic line clearing techniques. Recovery of native vegetation as measured by vegetation structure was also quantified.The audit found DME to have a dynamic and integrated environmental management system while company systems varied in standard. Wide consultation assisted the audit process.As a result of clearing for agriculture, native vegetation covers only six per cent of the Otway Basin. With the strict limitations to broad-scale vegetation clearance since the mid-1980s and the cessation since 1991, the greatest environmental impact of seismic exploration is the clearance of native vegetation for access by seismic vehicles. Native vegetation structure and associated abiotic variables on seismic lines and adjacent control sites, were subject to a classification and ordination analysis which compared the impact of seismic lines constructed by bulldozer or Hydro-ax (industrial slasher). Post-seismic recovery rates of three different vegetation associations were also determined. This analytical technique permits the effects of seismic line clearance to be compared with the natural variability of specific vegetation associations within a region. In interpreting the results however, there is a confounding effect of line type and year as most of the more recent seismic lines were constructed using a Hydro-ax. Results indicate that Hydro-ax clearing affects vegetation structure less than bulldozing. Most Hydro-ax sites recovered within a few years whereas some sites, bulldozed as early as 1971, particularly tussock grasslands, have not yet recovered.This study provides a significant break-through in the debate about the persistence of seismic impacts on native vegetation. As a rapid preliminary assessment, sampling vegetation structure rather than floristics, provides a cost-effective audit and monitoring technique which can be used by non-specialists in a range of petroleum exploration environments. Any significant structural differences may require more detailed analysis to determine if floristic composition also differed.

ACCESS TO LAND FOR EXPLORATION — THE ADOPTION OF MULTIPLE LAND USE PRINCIPLES IN SOUTH AUSTRALIA

1988 ◽  
Vol 28 (1) ◽  
pp. 325
Author(s):  
O. Morozow
Keyword(s):  
Land Use ◽  
National Parks ◽  
State Government ◽  
South Australia ◽  
Careful Consideration ◽  
Petroleum Exploration ◽  
Petroleum Potential ◽  
Multiple Land Use ◽  
Legislative Changes ◽  
Surface Mineral

The continued access to land for exploration by the petroleum and mineral industries in Australia has been increasingly impeded by State and Commonwealth legislation aimed at dedicating Crown Land for single land uses.In September 1986, South Australia's Minister for Mines and Energy, Ron Payne, announced a Cabinet decision for 'a package of recommendations designed to foster multiple land-use concepts and to ensure that no land is alienated from exploration without careful consideration of the sub-surface mineral/petroleum potential, relevant economic factors and the existing and potential sub-surface rights'.In this one innovative and potentially far-reaching move, the South Australian Government has:provided a framework to reconcile conflicting interests;indicated a willingness to listen and act upon the expressed legitimate concerns of industries of vital economic importance to the State;made it necessary for the proponents of reserve areas such as National Parks to be more accountable and to provide balanced, scientific substantiation;indicated its intention to make legislative changes to allow for the adoption of multiple land-use principles; andredressed the imbalance where, in the words of the Minister, 'Legislation providing for Aboriginal land rights, the creation of national and conservation parks, and State Government heritage areas have, to varying degrees, created unforeseen consequences for the resources industry'.The first practical test of this new Government policy is the proposed declaration of the Innamincka Regional Reserve, currently a 14 000 sq km pastoral lease within some of the most productive areas of PELs 5 & 6 held jointly by Santos Ltd. and Delhi Petroleum Pty. Ltd.It is intended that this new form of reserve will allow for the protection of specific areas of environmental sensitivity and of cultural, scientific and historic value, while still allowing for the continuation of pastoral, tourist and petroleum exploration/ production activity within the major part of the reserve area.

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