0
20
40
60
80
100
120
140
160
180
200
MM
BO
E
Petrel Tern Blacktip
Fields
Field Reserves
Gas
Oil/Condensate
0
10
20
30
40
50
60
MM
BO
E
Resource discovery in the next 10-15 years
Oil
Gas
Condensate
6. PERMIAN HYLAND BAY/KEYLING-HYLAND BAY (.) PETROLEUM SYSTEM
(Central Petrel Sub-basin)
Petroleum System Characteristics
Source Reservoir Seal Source Quality Source Type System Age Expulsion
Traps Risk
Key References
The Permian Hyland Bay/Keyling-Hyland Bay (.) petroleum system is located within the central Petrel Sub-basin of the Bonaparte Basin.
The Petrel Sub-Basin is an asymmetric northwest trending rift of Late Devonian-Carboniferous age, containing up to 15 km of Palaeozoic and Mesozoic sediments.The dominant source rock in the central Petrel Sub-basin is the oil and gas prone Keyling Formation. Modelled expulsion from the Keyling Formation is widespread in the central and outer Petrel Deep, commencing in the Late Permian and peaking in the Early Triassic. Minor expulsion continued throughout the Late Triassic-Cretaceous. The distribution and thickness of the oil prone facies is poorly known but there are indications for an oil system with low confidence Synthetic Aperture Radar (SAR) slick anomalies east and southeast of the Petrel gas field.Modelled gas expulsion from the Hyland Bay Formation is restricted to the outer part of the Petrel deep and the adjacent Malita Graben. Expulsion began in the Jurassic with peak expulsion in the mid-late Cretaceous. The formation is too lean to expel oil.
Jurassic units are important source sequences in other areas of the Bonaparte Basin but in the Petrel Sub-basin they are immature for hydrocarbon generation.The primary exploration target in this region is the deltaic Hyland Bay Formation with widespread sands. Reservoir distribution is considered a risk in this system. Typically reservoirs are thin, lenticular, isolated, low permeability and have high water saturation. The overlying Mt. Goodwin Formation forms a regional seal.
To date there has been no commercial hydrocarbon production in the Petrel Sub-basin. This gas-prone system has proven hydrocarbon potential with six gas discoveries; Blacktip, Fishburn, Leseuer, Penguin, Petrel and Tern. Development of the Petrel, Tern and Blacktip fields is being considered.
Figure 1: Spatial extent of the Hyland Bay/Keyling-Hyland Bay (.) petroleum system. The source pod limit is based on thermal maturation modelling by Kennard et al. (2002). The petroleum system limit has been confined to the Petrel Sub-basin.
Figure 2: Permian Hyland Bay/Keyling-Hyland Bay (.) petroleum system map showing hydrocarbon accumulations and shows thought to have been sourced from either the Keyling or Hyland Bay Formations. Expulsion from the Keyling Formation is widespread in the central and outer Petrel Deep. Gas expulsion from Hyland Bay Formation is more restricted to the outer part of Petrel deep and the adjacent Malita Graben. The seismic line shown refers to Figure 4.
Figure 4: GA seismic line 100-05 (part) transect of the Petrel Sub-basin. This seismic line displays an example of the play elements for the Permian Hyland Bay/Keyling-Hyland Bay (.) petroleum system. The Keyling (gas and possibly oil) and the Hyland Bay (gas) formations act as both source and reservoirs within the area. The hydrocarbons are trapped by the Mt Goodwin Formation regional seal and migrate into structures such as the Petrel/Tern inversion anticlines. The Bougainville-1 well is an example of a salt diaper play. Unfortunately at this location only gas indications were found within the well. Trap types in this region include salt related plays, faulted anticlines, large scale inversion anticlines and stratigraphic traps/pinchouts.
Figure 5: Schematic diagram of the Permian Hyland Bay/Keyling-Hyland Bay (.) petroleum system.
Figure 7: Geoscience Australia (Austplay) estimate of the recoverable hydrocarbons to be discovered in the next 10-15 years in the Permian Hyland Bay/Keyling-Hyland Bay (.) petroleum system. Based on the work of Barrett et al. (2004).
Figure 8: Modelled oil and gas expulsion time plots for the Keyling Formation source unit. Expulsion from the Keyling Formation is widespread in the central and outer Petrel Deep (Figure 2), commencing in the Late Permian and peaking in the Early Triassic. Minor expulsion continued throughout the Late Triassic-Cretaceous. The oil prone facies thickness and distribution is poorly known and to date no oil discoveries have been made.
Figure 6: Geohistory plot for the Petrel 2 well. At this location the Hyland Bay Formation has been at sufficient depths since the mid Cretaceous for oil and gas generation, but this unit is gas prone.
Figure 9: Modelled gas expulsion time plots for the Hyland Bay source unit. Gas expulsion from Hyland Bay is restricted to outer part of Petrel deep and the adjacent Malita Graben. Expulsion occurred in the Jurassic to Cretaceous.
Figure 10: Rock-Eval pyrolysis data for potential Permian source rocks in the Petrel Sub-basin. The Keyling Formation source quality ranges from dry gas prone Type III/IV kerogen to oil-condensate prone Type II/III kerogen. Coaly facies (mean TOC = 35%) have the potential to generate oil and gas but are thin and immature. The Hyland Bay Formation is gas prone with type III/IV kerogen and an overall poor generative potential.
Figure 11: Chronostratigraphy; Petrel Sub-basin. Figure 12: Cross-section; Petrel Sub-basin.
Keyling and Hyland Bay FormationKeyling and Hyland Bay FormationMount Goodwin FormationGas proneCoaly mudstones, mudstonesPermianKeyling Formation - Late Permian to Early CretaceousHyland Bay Formation - Jurassic to Late CretaceousFaulted anticlines, salt diapir associated structures, stratigraphicGeneral perception that the Petrel Sub-basin lacks regionally extensive and high quality reservoirs Acreage Release 2002.
Barrett, A.G., Hinde, A.L. & Kennard, J.M., 2004. Undiscovered resource assessment methodologies and application to the Bonaparte Basin. In: Ellis G.K., Baillie P.W. and Munson T.J. (Eds) Timor Sea Petroleum Geoscience. Proceedings of the Timor Sea Symposium, Darwin, Northern Territory, 19-20 June 2003. Northern Territory Geological Survey, Special Publication 1.
Kennard, J.M., Deighton, I., Edwards, D.S., Boreham, C.J., & Barrett A.G., 2002. Subsidence and thermal history modelling: New insights into hydrocarbon expulsion fro multiple petroleum systems in the Petrel Sub-basin, Bonaparte Basin. The Sedimentary Basins of Western Australia 3: Proceedings of the Petroleum Exploration Society of Australia Symposium, Perth,WA, 2002, 409-437.
Figure 3: Field reserves for the Permian Hyland Bay/Keyling-Hyland Bay (.) Petroleum system. All reserve numbers are sourced from the Western Australian Geological Survey and Northern Territory Government Department of Business, Industry and Resource Development. Reserves/resources are estimated by the Department and exploration companies.
Petroleum Systems of the Bonaparte Basin© Commonwealth of Australia 2004
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