Origin Energy has committed to drill a deepwater exploration well into the large double prospect Carrack and Caravel which lies 65 km east of the South Island city of Dunedin.
Origin's executive general manager exploration, Rob Willink said the Carrack/Caravel prospect is very large by any comparative standard and is located in an established petroliferous basin.
Carrack/Caravel has a combined areal extent of some 300 sq km at top Cretaceous reservoir level. The structure is estimated to contain a mean of 750 million barrels of recoverable oil in Herbert Formation reservoirs if it is oil charged, or 2.7 trillion cubic feet of recoverable gas and 500 million barrels of associated condensate if it is gas charged.
Should hydrocarbons also be trapped in the lower Kawau sandstone reservoirs, recoverable hydrocarbon volumes could more than double, Mr Willink says.
But a well on this 1,000 metre deep water prospect remains subject to considerable technical risk, he said.
Origin Energy Resources (NZ) Ltd is the operator of the 100% controlled PEP 38262 permit in the offshore Canterbury Basin.
The prospect complex has been matured to drillable status by a tight grid of 2D seismic data recently acquired by Origin. The prospect has two distinct structural culminations which are separately referred to as Caravel in the north and Carrack in the south.
Potential reservoir objectives are inferred to be the Cretaceous Herbert Formation and Kawau Sandstone, both established hydrocarbon bearing in the nearby Galleon 1 well, drilled by Shell BP Todd Canterbury Services Ltd in 1985.
A drill stem test at Galleon 1 flowed gas at 10.6 million cubic feet per day and associated condensate at 2,240 barrels per day.
Mr Willink said a deep water drilling rig would be required to drill a well, but these were expensive and difficult to source in the current tight global rig market.
Origin is currently seeking other partners for this high risk, but potentially high reward exploration opportunity.
Origin has also started talking with a number of drilling management services companies and the operators of nearby permits that are facing drilling in a similar time frame, to secure a suitable rig, Mr Willink said.