An oil exploration ship has left Dunedin to begin a four month survey of the sea floor off New Zealand's south-eastern coast.
In August, Shell New Zealand joined a consortium led by OMV, an Austrian oil company, to explore a large area of the Great South Basin for oil and gas.
OMV's exploration permits cover more than 30,000 square km of seabed off the coast of Dunedin.
The Polarcus Alima and a supply ship stopped briefly in Dunedin on Wednesday before heading out to sea for about 120 days.
The company says it has already spent $50 million to date exploring the basin, and this next phase of three-dimensional mapping is expected to cost about $30 million.
If a potential gas or oil field is located, Shell New Zealand will consider drilling a test well in about 2 years.