Ordovician Petroleum Systems: Canning Basin’s Emerging Potential, Western Australia
K. Ameed R. Ghori
Geological Survey of Western Australia, Department of Mines and Petroleum, East Perth, Australia
This paper reviews global Ordovician petroleum systems and emerging source-rock selfcontained petroleum resources in the Canning Basin, Western Australia. Productivity of the Ordovician sourced and reservoired petroleum systems is low among Phanerozoic petroleum systems, which depends on source facies and richness, and charge timing and preservation; these risks are low in source-rock self-contained petroleum systems.
Ordovician petroleum systems evolved and separated as a part of Pangaea–Gondwana supercontinents amalgamation and breakup through geological time. Marine transgression and oceanic anoxia during the Ordovician Period (488–444 Ma) deposited widespread oilprone petroleum source rocks within the Chinese Tarim Basin, the North American intracratonic basins, the European Baltic Basin, and the Australian Amadeus and Canning basins.
Ordovician organic facies is mainly derived from Gloeocapsomorpha prisca and marine algae, and are composed of amorphous and telalginitic kerogen. Generally, organic richness is up to 5% TOC, hydrogen indices are up to 500 mg HC/g TOC, and maturity is from immature to gas mature. Locally, source beds are very high in organic richness; the richest example is the Estonian Kukersite oil shale of Europe, 77% TOC. In the United States, Ordovician oil generated and preserved includes several giant oil fields, containing over 100 million bbl of oil. The Bongabinni Formation of the Canning Basin contains up to 60% TOC.
The Ordovician Goldwyer Formation of the Canning Basin contains rich oil-prone sourcebeds, with up to 5% TOC and hydrogen indices are up to 850 mg/g TOC on the Barbwire Terrace. Significant oil and gas discovered at Pictor and Dodonea areas, and oil recovered in Percival 1, Solanum 1, Edgar 1, Cudalgarra 1, Great Sandy 1 and Leo 1, correlate with the Goldwyer Formation. These petroleum systems are present within the Ordovician–Silurian succession, where reservoirs within the Nita and Willara formations are overlain by thick salts of the Carribuddy Group with excellent sealing capacities. The succession is sandwiched between favourable tectonics for trap developments: Early Ordovician extension and Early Devonian compression.
The Goldwyer Formation has an average thickness of about 400 m and the thickest intersection is 736 m; its estimated shale-gas resource is up to 288 trillion cubic (Tcf). Exploration is at a very early stage, and more work is needed to verify these estimates. New Standard Nicolay 1 is the first well drilled to evaluate shale-gas potential within the Goldwyer Formation. Petroleum systems of the Goldwyer Formation are summarized in Figure 1.
AAPG Search and Discovery Article #90175©2013 AAPG Hedberg Conference, Beijing, China, April 21-24, 2013