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Oil giant Anadarko has this week been granted a five-year extension for its exploration permit in the southern sector of the Canterbury Basin, north of Dunedin.
The extension, by Government permitting agency New Zealand Petroleum & Minerals, is not an indication of an increasing likelihood of more drilling, which will be decided by the Houston-based company by October.
More ship-borne seismic data collection may yet precede any decision on a second southern drilling programme.
Analysis of core samples from Anadarko's $120 million drilling programme in March, 60km north of Dunedin at the Caraval prospect off Oamaru, had not yet been completed, Anadarko New Zealand corporate affairs spokesman Alan Seay said when contacted yesterday.
''We're making good progress with the analysis. We captured significant new data for both Caraval and Romney [off Taranaki] to help in determining drilling,'' he said.
While the Caraval test well was capped and abandoned, there had been ''shows'' of oil and gas but not in commercially viable quantities, as with Romney.
''If we advance to the next step, there will probably be more seismic data [ship surveying] to determine if there will be additional drilling required,'' he said of further Canterbury Basin exploration.
Mr Seay said it was likely a decision would be made by October, and if seismic surveying went ahead, it could be in the more stable ''seasonal weather window'' around January to March next year.
He understood there were seismic survey vessels available during that period, which were undertaking other work around the country.
Anadarko had not made any plans to ''pencil in'' a drillship or platform for a possible drilling programme, he said.
During its January to March programmes, Anadarko used the drillship Noble Bob Douglas for test wells in both Taranaki and off the Otago coast, at a cost of more than $400 million in total.
It is the prospect of drilling in deep water which has most concerned environmentalists, following the Deepwater Horizon disaster and oil spill in the Gulf of Mexico, and later the effects of the oil spill from the grounded container ship Rena in New Zealand.
Off Otago, the test well was in 1100m of water, drilling about 1700m below the seabed to 2800m, while in Taranaki, the drilling was at depths of 1500m, to a total depth 4600m.