Observations on the Lower Triassic petroleum prospectivity of the offshore Carnarvon and Roebuck basins
Stephen Molyneux A , Jeff Goodall A , Roisin McGee A , George Mills A and Birgitta Hartung-Kagi BA Carnarvon Petroleum
B Canarvon Petroleum
The APPEA Journal 56(1) 173-202 https://doi.org/10.1071/AJ15014
Published: 2016
Abstract
Why are the only commercial hydrocarbon discoveries in Lower Triassic and Permian sediments of the western margin of Australia restricted to the Perth Basin and the Petrel Sub-basin?
Recent regional analysis by Carnarvon Petroleum has sought to address some key questions about the Lower Triassic Locker Shale and Upper Permian Chinty and Kennedy formations petroleum systems along the shallow water margin of the Carnarvon and offshore Canning (Roebuck/Bedout) basins. This paper aims to address the following questions:
Source: Is there evidence in the wells drilled to date of a working petroleum system tied to the Locker Shale or other pre-Jurassic source rocks?
Reservoir: What is the palaeogeography and sedimentology of the stratigraphic units and what are the implications for the petroleum systems?
The authors believed that a fresh look at the Lower Triassic to Upper Permian petroleum prospectivity of the North West Shelf would be beneficial, and key observations arising from the regional study undertaken are highlighted:
Few wells along a 2,000 km area have drilled into Lower Triassic Locker Shale or older stratigraphy.
Several of these wells have been geochemically and isotopically typed to potentially non Jurassic source rocks.
The basal Triassic Hovea Member of the Kockatea Shale in the Perth Basin is a proven commercial oil source rock and a Hovea Member Equivalent has been identified through palynology and a distinctive sapropelic/algal kerogen facies in nearly 16 wells that penetrate the full Lower Triassic interval on the North West Shelf.
Samples from the Upper Permian, the Hovea Member Equivalent and the Locker Shale have been analysed isotopically indicating –28, –34 and –30 delta C13 averages, respectively.
Lower Triassic and Upper Permian reservoirs are often high net to gross sands with up to 1,000 mD permeability and around 20% porosity.
Depositional processes are varied, from Locker Shale submarine canyon systems to a mixed carbonate clastic marine coastline/shelf of the Upper Permian Chinty and Kennedy formations.
Stephen Molyneux comes from a farming background in Lancashire, UK, and first became interested in rocks by looking at the glacial erratics in his family’s fields. From there it was O- and A-level geology, and a geology degree at Imperial College, London from 1985–88. Stephen started his working career at Enterprise Oil in London from 1989–94. He then completed a MSc in sedimentology at Birkbeck College London, and in 2000 completed an Imperial PhD in the seismic interpretation of oil-bearing sandstone intrusions of the North Sea. He had a short stint in 1999–2000 working for PanCanadian on the UK Buzzard discovery; he then went off to Calgary from 2000–08 to work for PanCanadian as the company’s deepwater specialist, working on projects such as the Buzzard discovery and offshore Brazil/Africa/GOM exploration. Stephen managed to luck out with a discovery in GOM at Tahiti, Brazil in the Peregrino discovery and Sergipe basins—all stratigraphic traps. Stephen then spent four years with Oilexco Calgary as Chief Geologist, working in the North Sea where the company drilled more than 50 offshore wells and found more then 100 million barrels of recoverable oil. Several fields were stratigraphic, and some had seismic scale sandstone intrusions. The GFC was not kind to Oilexco and in 2009 was bought by Premier. Stephen then had spells with Premier North Sea (lead explorer North Sea 2009–10), Origin Energy in Brisbane (as International New Ventures Manager, 2010–12), and is now with Carnarvon Petroleum in Perth. smolyneux@cvn.com.au |
Jeff Goodall graduated from University College London, and then spent a period of 10 years working on North Sea and West African projects. He then migrated to Australia to work for Santos, in Adelaide. Jeff’s roles in Santos included working in the stratigraphy group, and later as an exploration geologist working primarily on North West Shelf and Indonesian assets. After 14 years in Santos, Jeff moved to a stratigraphic and geological consultancy role and the building of the Morgan Goodall Palaeo laboratory and consulting business in Perth, involving a diverse range of regional geological projects and drilling campaigns on the North West Shelf and in Indonesia with Husky, AWE and CNNOC. In 2013, consulting work for Carnarvon Petroleum led to a full-time role, working on a variety of North West Shelf projects and helping develop ideas on the inboard Triassic exploration. jgoodall@cvn.com.au |
Roisin McGee graduated from the University of Leeds with a BSc in geophysical sciences. She then completed a MSc in petroleum geoscience at Imperial College London in 2009. Rosin began her career at Gaffney-Cline and Associates as a Junior Geoscientist, where she worked on various types of consulting projects from around the globe. She then moved to Norway, and was employed by Statoil, where she gained skills as a Development Geophysicist for the Oseberg Production Technology Group. Rosin joined Carnarvon Petroleum in 2013 as a geophysicist, where she continues to gain invaluable experience in new ventures and exploration in the basins of the North West Shelf. rmcgee@cvn.com.au |
George Mills graduated with a BSc (Hons) degree in geology and resource economics from the University of Western Australia in 2014. His thesis aimed to identify evidence for Neogene fault reactivation and linkage structures within the Southern Vulcan Sub-basin. In late 2014, George joined Carnarvon Petroleum as a geologist, where he is presently working on a number of projects on the North West Shelf, including the characterisation of the Hovea Member as an active source rock on the North West Shelf. gmills@cvn.com.au |
Birgitta Hartung-Kagi graduated with a MSc in geology from the University of Kiel (Germany) in 1977, and completed a PhD on the tectonics and sedimentology of the South Agaean Islands (Greece) at the Technical University of Braunschweig (Germany) in 1981. After three years as a research fellow at the German Petroleum Geochemistry Institut at KFA Juelich, she arrived in Australia in 1984 and worked for several Perth-based oil companies as a geologist/geochemist. In 1986, Birgitta joined Analabs as Manager—Oil and Gas, and in 1989 she established Geotechnical Services Pty Ltd, a major provider of geochemical, petrophysical and environmental services. She left Geotech in 2012, after 23 years as Managing Director, and is presently a geochemical consultant based in Perth. bmkagi@hotmail.com |
