By Neil Ritchie

OFFSHORE oil and gas exploration and development continues in New Zealand but further failures again highlight the difficulties of working in the Taranaki basin with its sometimes complex geology, as well as the urgent need for further finds to lift the country’s faltering petroleum production.

It is now 13 years since the last successful “wildcat” strike – the discovery of the Tui, Pateke and Amokura oil pools. “It’s looking pretty grim offshore at present… it would be so great to see some further successes,” one commentator told Oil & Gas Australia recently.

While this country’s gas production continues to climb, albeit slowly, thanks to incremental onshore developments, overall oil production is still sliding by about 13 per cent each year and now, at less than 40,000 barrels per day, is only about 30% of what it was six years ago.

The latest offshore failure is the plugging and abandoning of the Oi-2 well within the Tui Area field mining licence PEP 38158 after it failed to encounter any significant oil shows.

The semi-submersible Kan Tan IV rig reached a total depth of 3,908 metres and intersected the primary target, the Eocene-aged Kapuni F10 sands and underlying secondary targets.

However, no significant oil shows were encountered and well data indicated the reservoir was water bearing. This followed the earlier abandoning of the Oil-1 well due to drilling difficulties.

The Tui partners – operator Australian listed company AWE (57.5%), New Zealand Oil & Gas (27.5%) and Australia listed junior Pan Pacific Petroleum (15%) – had hoped the Oi prospect would contain 11-15 million barrels of recoverable oil.

But Pan Pacific took additional equity in the Oi-1 and 2 wells, taking a 50% stake, with AWE and NZOG’s shares dropping to 31.25% and 18.75% respectively.

“The Oi wells were a bit of a disaster for Pan Pac and leaves their cash pool depleted . . . they’re probably not big enough now to continue being an offshore player, which is a shame,” one commentator told Oil & Gas Australia recently.

After Oi-2, the Kan Tan moved to just south of the Maari-Manaia oil field to drill the Whio-1 exploration well, in exploration lease PEP 51313, for the Maari partners – operator OMV, Todd Energy and listed Australian juniors Horizon Oil and Cue Energy Resources.

An interesting aside is that OMV is seeking consent from the recently established Environmental Protection Authority to continue development drilling at the Maari wellhead platform in mining lease PEP 38160 as well as in the nearby PEP 51313 where the Whio-1 is being drilled.

OMV and partners have been drilling in accordance with the transitional provisions of the Exclusive Economic Zone Act.

However, these provisions ceased on 28 June meaning marine consents are required for drilling beyond this date.

They hope a commercial discovery in the Whio Prospect – particularly oil – would probably involve construction of a new wellhead platform linked back to the Maari facilities and extend the economic life of production in the area.

Whio is an Eocene-aged four-way dip closure believed to be similar to the offshore Maui and onshore Kapuni fields.

OMV is planning to drill a deviated ‘S’-bend well to at least 2,839 metres measured depth at Whio-1 with the well’s design helping to avoid possible gas pockets.

Meanwhile, the jack-up Ensco Rig 107 is still alongside the Maari wellhead platform and has finally finished workovers of existing production wells and a variety of other subsurface tasks.

It is now drilling the first of several new development and water injection wells.

Having two rigs operating at the same time is keeping the OMV New Zealand drilling engineers very busy.

But on the positive side, Maui field operator Shell Todd Oil Services has confirmed a fourth sidetrack well for the Archer Emerald modular offshore drilling unit (MODU) aboard the Maui A platform.

After drilling the MA-4A, MA-09B and MA-08A sidetrack wells, the unit is now drilling MA-06A after plugging and abandoning the bottom hole of the existing MA-06 well and deviating to drill the sidetrack.

This operation is expected to take three months or so for the Maui partners Shell Exploration New Zealand, Todd Energy and OMV.