Release Areas W16-24 and W16-25, Exmouth Sub-basin, Northern Carnarvon Basin, Western Australia

HighlightsBids close for Release Area W16-24 on 23 March 2017.

Prequalification for Release Area W16-25 closes on 20 October 2016, with the cash bidding auction to be held on 2 February 2017. One of Australia’s major oil producing provinces, adjacent to multi-Tcf gas fields Proximal to Macedon gas pipeline with tieback to onshore gas plant Shallow to deep water depths, 350–1100 m Oil-prone Upper Jurassic and gas-prone Triassic to Middle Jurassic source rocks Triassic fault block and Cretaceous stratigraphic traps Further guidance available, please refer to 2016 Special NoticesRelease Areas W16-24 and W16-25 are within the northern Exmouth Sub-basin, approximately 75-125 km north of Exmouth. W16-25 comprises two graticular blocks and is available for cash bidding, while the more northerly W16-24 comprises a larger area of twelve graticular blocks, with a slight extension into the southern Exmouth Plateau (Error: Reference source not found) and is available for work program bidding. The Release Areas are in the vicinity of numerous oil and gas accumulations including Vincent/Van Gogh, Pyrenees/Macedon, Skiddaw/Laverda, Stybarrow and Coniston (Error: Reference source not found).

The Exmouth Sub-basin formed as one of a series of northeast–southwest trending, en-echelon structural depressions during the Pliensbachian to Oxfordian. Pre-rift sediments are of Permian and Early to Middle Triassic age, and are gas-prone (Error: Reference source not found). The Upper Jurassic Dingo Claystone is the main oil-prone source rock within the Exmouth Sub-basin. Proven reservoirs occur within the Barrow Group and Dupuy Sandstone, with the Muderong Shale acting as the regional seal. Play types include fault block traps within the Mungaroo Formation with an intraformational or Dingo Claystone seal, stratigraphic plays within the Barrow Group and complex structural/stratigraphic Jurassic channel fill plays (Error: Reference source not found). Infrastructure is in-place for oil and gas production, with the Macedon gas pipeline in operation (Error: Reference source not found).

Error: Reference source not found shows the existing data coverage in the vicinity of the Release Areas, with only one well, Furness 1, being located within Release Area W16-25. Release Area W16-24 has 2D seismic coverage, with an average line spacing of less than 5 km, and is largely covered by the HCA04 3D seismic survey. Release Area W16-25 has 2D seismic coverage, with an average line spacing of less than 2.5 km, and is fully covered by the HCA2000A 3D seismic survey, and has additional coverage from the West-Gorgon 3D and Vincent 3D seismic surveys that overlap parts of the Release Area.

Petroleum systems elementsExmouth Sub-basin

Sources Jurassic marine Dingo Claystone (oil-prone) Lower to Middle Jurassic marine siltstone and claystones (oil- and gas-prone) Triassic fluvio-deltaic sediments of the Mungaroo Formation (gas-prone)

Reservoirs Lower Cretaceous Winning Group and fluvio-deltaic Barrow Group, Mardie Greensand Member, Zeepaard Formation and Birdrong Sandstone

Upper Jurassic, deep marine sandstones of the Dupuy Formation where present Triassic, fluvio-deltaic sandstones of the Mungaroo Formation and shallow marine-deltaic

sandstones of the Brigadier Formation

Seals Regional seal

Lower Cretaceous, marine Muderong Shale

Intraformational seals

Upper Triassic deltaic sequences of the Mungaroo Formation

Plays Cretaceous inversion anticline structural/stratigraphic plays Complex Jurassic structural/stratigraphic plays Tilted Triassic fault blocks and associated drapes

Infrastructure and marketsThe Release Areas are in proximity to oil production facilities, existing multi-Tcf gas fields and recent discoveries. The new pipeline infrastructure connecting the Macedon gas accumulation to a processing plant provides future tie-in opportunities. LNG facilities in the region are currently under construction, with more being planned.

Critical risksAccess to hydrocarbon charge and reduced reservoir quality, due to diagenetic overprinting, are the main risks. The western extent of Release Area W16-24 may not be within the migration pathway of the Dingo-sourced oil charge. Lithological variations within potential seal facies in the Barrow Group and Dupuy Formation may result in inadequate seals for commercial hydrocarbons in some locations. The depth to the Triassic sequence in the central Exmouth Sub-basin may limit the viability of tilted Triassic fault block plays for W16-25 and parts of W16-24.

Marine and Environmental information

Release Area W16-24 Release Area W16-24 is located 60 km from the Pilbara coastline and 50 km from South Murion Island, in water

depths of 372-1128 m.

Seabed sediment is dominantly sandy mud in texture, with significant input from planktonic foraminifers and pteropods (Baker et al., 2008, Colwell and von Stackelberg, 1981).

There is no detailed information on the shallow subsurface geology (< 100 m).

Partly overlies Continental Slope Demersal Fish Communities.

The eastern part of W16-24 is positioned over ‘slope’ geomorphology and the western part over the southern end of a large trough. Potential hazards may include tropical cyclones.

Commonwealth Marine ReservesThe western margin of release area W16-24 is directly adjacent to Gascoyne Multiple Use Zone IUCN VI Commonwealth Marine Reserve. W16-24 is located 46 km north of Ningaloo IUCN Category II Recreational Use Zone Commonwealth Marine Reserve.

Key Ecological FeaturesThere are five Key Ecological Features in the region, and Release Area W16-24 overlaps one (National Conservation Values Atlas, 2016). These are:

the Canyons on the slope between the Cuvier Abyssal Plain and the Cape Range Peninsula, located 22 km south of the area (enhanced productivity, aggregations of marine life and unique sea-floor feature),

the Exmouth Plateau (*KEF, a unique sea-floor feature associated with internal wave generation), located 20 km to the northwest at the closest point,

the Continental Slope Demersal Fish Communities (high species diversity and endemism - the most diverse slope bioregion in Australia with over 500 species found, of which over 64 of those species occurring nowhere else) is overlapped by W16-24,

the Ancient Coastline at 125 m depth located approximately 41 km to the east, and

the Commonwealth waters adjacent to Ningaloo Reef, located 46 km to the south, defined as the waters contained in the existing Ningaloo Marine Park (Commonwealth Waters).

Biologically important areasRelease Area W16-24 intersects the following biologically important areas (National Conservation Values Atlas, 2016):

Overlaps the Humpback Whale migration corridor and is within the known distribution for Pygmy Blue Whales.

Includes threatened and migratory Flatback, Green, Hawksbill and Loggerhead Turtle foraging areas.

Includes vulnerable and migratory whale sharks foraging areas.

Overlaps foraging areas for the migratory seabirds; the Wedge-tailed Shearwater and Fairy Tern. Breeding for these species occurs throughout most of the year as indicated in Table 1.

Ja Fe Ma Ap Ma Ju Ju Au Sept

Oc No De

Fairy Tern b b b

Wedge-tailed Shearwater

b b b b b b b b b b

Table 1 Breeding periods (b) for key seabirds whose foraging areas overlap Release Area W16-24

Release Area W16-25 Release Area W16-25 is located 45 km from the Pilbara coastline and 45 km from South Murion Island, in water

depths of 516-725 m. The southern boundary to W16-25 is ~ 2.5 km north of a large westward-deepening submarine canyon.

Seabed sediment texture is likely to be sandy mud or similar, and dominated by planktonic foraminifers and pteropods (Colwell and von Stackelberg, 1981).

There is no detailed information on the shallow subsurface geology (< 100 m).

W16-25 partly overlaps the continental slope demersal fish communities, a Key Ecological Feature.

Potential hazards may include tropical cyclones.

Commonwealth Marine ReservesGascoyne Multiple Use Zone IUCN VI Commonwealth Marine Reserve is located to the west of W16-25. Ningaloo IUCN Category II Recreational Use Zone Commonwealth Marine Reserve is located to the south.

Key Ecological FeaturesThere are five Key Ecological Features in the region, and Release Area W16-25 overlaps one (National Conservation Values Atlas, 2016). These are:

the Canyons on the slope between the Cuvier Abyssal Plain and the Cape Range Peninsula, located 4 km south of W16-25 (enhanced productivity, aggregations of marine life and unique sea-floor feature),

the Exmouth Plateau (*KEF, a unique sea-floor feature associated with internal wave generation), located 50 km to the northwest at the closest point,

the Continental Slope Demersal Fish Communities (high species diversity and endemism - the most diverse slope bioregion in Australia with over 500 species found with over 64 of those species occurring nowhere else), overlaps W16-25,

the Ancient Coastline at 125 m depth, located 55 km to the east, and

the Commonwealth waters adjacent to Ningaloo Reef, located 28 km to the south, defined as the waters contained in the existing Ningaloo Marine Park (Commonwealth Waters).

Biologically Important AreasRelease Area W16-25 intersects the following biologically important areas (National Conservation Values Atlas, 2016):

Overlaps a Humpback Whale migration corridor and is within the known distribution for Pygmy Blue Whales.

Includes threatened and migratory Flatback, Green, Hawksbill and Loggerhead Turtles foraging areas.

Includes vulnerable and migratory whale shark areas.

Overlaps foraging areas for migratory seabirds; the Wedge-tailed Shearwater and Fairy Tern. Breeding for these species occurs throughout most of the year as indicated in Table 2.

Jan Fe Mar Apr Ma Jun Jul Aug Sept Oct Nov Dec

Fairy Tern b b b

Wedge-tailed Shearwater b b b b b b b b b b

Table 2 Breeding periods (b) for key seabirds whose foraging areas overlap Release Area W16-25.

Note: *KEF indicates the Exmouth Plateau in the sense of a Key Ecological Feature as identified in the North-west Marine Bioregional Plan (Commonwealth of Australia, 2012), prepared under the Environment Protection and Biodiversity Conservation Act 1999. This is different from, though related to, the Exmouth Plateau in the geological sense.

Information Resources National Conservation Values Atlas http://www.environment.gov.au/webgis-framework/apps/ncva/ncva.jsf

Gascoyne Commonwealth Marine Reserve http://www.environment.gov.au/topics/marine/marine-reserves/north-west/gascoyne

Montebello Commonwealth Marine Reserve http://www.environment.gov.au/topics/marine/marine-reserves/north-west/montebello

Western Australian Marine Parks and Reserves https://www.dpaw.wa.gov.au/management/marine/marine-parks-and-reserves#

Commonwealth Fisheries http://www.afma.gov.au/fisheries/

Heritage https://www.environment.gov.au/topics/heritage

Geoscience Australia productsRegional geology and seismic Line Drawings of AGSO-Geoscience Australia’s Regional Seismic Profiles, Offshore Northern and Northwestern

Australia, 2001. GEOCAT 36353

Seismic Transects of Australia’s Frontier Continental Margins, 2006. GEOCAT 64054

Interpreted Horizons and Faults Data for Seismic Survey 95. Carnarvon and Roebuck Basins, 2003. GEOCAT 35234

Interpreted Horizons and Faults Data for Seismic Survey 101. Carnarvon Basin, 2003. GEOCAT 35240

Interpreted Horizons and Faults Data for Seismic Survey 110. Carnarvon Basin, 2003. GEOCAT 35242

Interpreted Horizons and Faults Data for Seismic Survey 128. Outer Carnarvon, Roebuck and Browse Basins, 2003. GEOCAT 35247

Geological Framework of the Outer Exmouth Plateau and Adjacent Ocean Basins, 2004. GEOCAT 60864

Carnarvon Cretaceous-Tertiary Tie Report, 1996. GEOCAT 25187

Stratigraphy Geoscience Australia’s Basin Biozonation and Stratigraphy Chart Series: Northern Carnarvon Basin Biozonation and

Biostratigraphy Chart 36, 2013. GEOCAT 76687

Petroleum systems and accumulations Source Rock Time-slice Maps (TOC, HI, VR), Offshore Northwest Australia —1:3,000,000 scale, 2004.

GEOCAT 61179

The Oils of Western Australia II, 2005. GEOCAT 37512

Australian Petroleum Systems. Barrow-Exmouth Sub-basins Module, 1994. GEOCAT 37163

Contact Geoscience Australia’s Sales Centre for more information or to order these reports or products, phone +61 (0)2 6249 9966, email sales@ga.gov.au

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