Earlier this week NZOG believed the targeted Kapuni C sands had been intersected, though only minor oil shows were encountered which were not considered to be commercially significant.

However, this morning exploration manager Eric Matthews said from the well site, 75km northeast of New Plymouth, that the complex geology of the Taranaki Basin had tricked NZOG.

"We went into sandstones, which we thought were the Kapuni. However, the results of logging showed them to be the Turi formation immediately above the Kapuni.

"So we need to keep drilling and expect to hit the Kapuni sands within the next few days, within the next 100 metres or so."

Drilling had resumed after the wireline logging and early this morning was at a depth of 2940m. The Kapuni C sands were expected to be encountered around the 3000m depth.

Matthews said the complex Taranaki geology often "tricked" explorers, with formations appearing similar to those being targeted being encountered. "That's why we run logs, to make sure we have got to where we want to be."

Opito-1 is a rank wildcat and the first exploration well to be drilled in PEP 38729. It is being drilled from a coastal drilling site and is targeting the Kapuni C sands within the Opito prospect, a mapped closure of over 44 square kilometres with the potential to hold more than 200 million barrels of oil.

Over 400m of Kapuni C sands, with good oil shows throughout, were encountered in the offshore Waihi-1 well, drilled some 20km to the southwest of Opito in 1993.