2018 Release Areas

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Acreage Release 2018: Bonaparte Basin

The Bonaparte Basin is located predominantly offshore and covers an area of approximately 270 000 km2 on Australia’s northern continental margin (Figure 1). It contains a Paleozoic, Mesozoic and Cenozoic sedimentary succession which exceeds 15 000 m in thickness (Figure 2, Figure 3 and Figure 4), and is a producing oil and gas province (Figure 5). Gas in the Bonaparte Basin is produced from the Bayu-Undan and Blacktip fields and oil is produced from the Laminaria-Corallina and greater Montara fields. The Petrel-Tern-Frigate, Barossa-Caldita, Cash-Maple, Greater Sunrise and Evans Shoals gas fields are being considered for development, while the former Buffalo oil field is being considered for re-development.

As of November 2017, the total oil and natural gas liquids, and natural gas and ethane 2P reserves (proved and probable) for the Bonaparte Basin are 29 MMbbls (4.61 GL) and 860 PJ, respectively (EnergyQuest, 2017). This includes net entitlement to Australia resulting from the Joint Petroleum Development Area production.

The 2018 Acreage Release offers an opportunity in the northwestern part of the basin (Figure 1 and Figure 6), with adjoining Release Areas AC18-1 and W18-1 overlying the northernmost Londonderry High where it is encircled by the Vulcan Sub-basin, Nancar Trough, Sahul Syncline and Echo Syncline basin elements. Numerous hydrocarbon shows indicate active petroleum systems are present (Figure 7), presumably sourced from the thick Paleozoic–Mesozoic section underlying the Release Areas as imaged by seismic (Figure 8).

Release Area AC18-1, Vulcan Sub-basin, Londonderry High and Nancar Trough, Bonaparte Basin, Territory of Ashmore and Cartier Islands

Highlights

Bids close 18 October 2018

  • Shallow to moderate water depth of 100–500 m

  • Proven oil and gas producing province; adjacent to the former producing Jabiru and Challis-Cassini oil fields to the southwest

  • Hydrocarbon shows in several wells, with proximal non-commercial discoveries of gas at Halcyon 1 and Delamere 1 and oil at Katandra 1A and Ludmilla 1

  • Release Area proximal to Jurassic depocentres with oil- and gas-prone source rocks

  • Potential for migration into structural and stratigraphic Triassic–Jurassic, Cretaceous and Paleogene plays

  • Further guidance available, refer to 2018 Special Notices

Release Area AC18-1 covers 3460 km2 and is centred on the northeastern flank of the Vulcan Sub-basin where it abuts the northwestern flank of the Londonderry High and southern limit of the Nancar Trough (Figure 6). The Release Area lies in water depths of 100–500 m, deepening to the northwest. The Release Area’s eastern boundary adjoins Release Area W18-1 and is defined by the jurisdictional boundary between the Territory of Ashmore and Cartier Islands and the state of Western Australia. Release Area AC18-1 consists of 34 full graticular blocks and 17 part graticular blocks.

Eleven exploration wells lie within Release Area AC18-1 (Table 1) and provide geological control, of which four (Jarrah 1A, Kingtree 1, Keppler 1 and Lorikeet 1) encountered hydrocarbons (Figure 6 and Figure 7), although no accumulations have been mapped. Exploration has largely focused on sandstone targets within the Jurassic Plover and Vulcan formations, with both Triassic and Eocene sections also being investigated (Figure 7). Trap-fault breach, lack of charge and poorly understood migration pathways have been interpreted as the main reasons for failure. Since effective source rocks and good reservoirs are prevalent in the area, future exploration success will hinge on a better understanding of migration pathways from Jurassic source kitchens, trap geometry and fault behaviour post trap charge.

Release Area AC18-1 is completely covered by 2D seismic and almost completely covered by 3D seismic (Figure 9). The 3D coverage predominantly comprises Onnia North 3D, acquired in 1998–99, with the most recent survey being Rissa 3D, acquired in 2011–12, over the northeastern corner.

Release Area W18-1, Sahul Syncline and Londonderry High, Bonaparte Basin, Western Australia

Highlights

Bids close 18 October 2018

  • Shallow water depth of 50–200 m

  • Adjoining proven oil and gas producing province; producing Bayu-Undan gas field to the east

  • Hydrocarbon shows in several wells, with a non-commercial gas discovery at Halcyon 1

  • Release Area flanked by Jurassic depocentres with oil-and gas-prone source rocks

  • Potential for migration into structural and stratigraphic Triassic–Jurassic, Cretaceous and Paleogene plays

  • Further guidance available, refer to 2018 Special Notices

Release Area W18-1 covers 4505 km2 and overlies the northern extremity of the Londonderry High and western edge of the adjoining Echo/Sahul synclines (Figure 6). The Release Area lies in water depths of 50–200 m, deepening to the northwest. The Release Area’s western boundary adjoins Release Area AC18-1 and is defined by the jurisdictional boundary between the Territory of Ashmore and Cartier Islands and the state of Western Australia. Release Area W18-1 consists of 43 full graticular blocks and 19 part graticular blocks.

Twelve exploration wells lie within Release Area W18-1 (Table 1) and provide geological control, while nine encountered hydrocarbons (Figure 6 and Figure 7), although no accumulations have been mapped. Exploration has largely focused on sandstone targets within the Triassic Nome and Challis formations, Jurassic Plover Formation and upper Jurassic–lower Cretaceous Sandpiper Sandstone. The main reasons for failure have been interpreted as trap-fault breach or trap tilt, lack of charge and poorly understood migration pathways. Since effective source rocks and good reservoirs are prevalent in the northern and southwestern parts of the Release Area, future exploration success will hinge on a better understanding of migration pathways from Jurassic source kitchens, trap geometry and fault behaviour post trap charge. The southeastern part of the Release Area relies upon the generation of hydrocarbons from the Upper Paleozoic successions into Triassic reservoirs and the mapping of competent traps of sufficient size below the Valanginian unconformity (Figure 8).

Release Area W18-1 is completely covered by 2D seismic and partly covered by 3D seismic (Figure 9). The 3D coverage predominantly comprises Onnia North 3D, acquired in 1998–99, and Rissa 3D, acquired in 2011–12, over the western and northern parts, respectively. The most recent 3D seismic survey is Tamar 3D, acquired in 2012 over the southeastern corner.