New Zealand Oil and Gas (NZOG) has lost about $US2.5 million as a result of a failed well off the coast of Taranaki.
Drilling on the Oi-1 reached just over 1500 metres when it hit technical difficulties and it will now be sealed and abandoned.
Another well, Oi-2, will be drilled nearby and will have improved procedures to line the walls of the well.
Before the failure, NZOG estimated it would have to pay $US5 million towards the drilling project. That's sum has risen to $US7.5 million.
The total project cost has gone up from $US27 million to $US40 million.