Field operator Shell Exploration New Zealand this week confirmed that all three production wells – drilled from the Motunui coast north of New Plymouth by the Ensign International Rig 41 – broke the previous New Zealand record for their length.

Rig 41, the largest land-based rig yet seen in New Zealand and imported from Indonesia especially for the onshore drilling of the Pohokura project, spent over a year drilling the three production wells and a water-disposal well.

The Pohokura-1 and 2 wells both exceeded 6500m in total length, surpassing the old record of 5661m set by a development well drilled in the Shell NZ-Todd Energy owned onshore Kapuni gas field in south Taranaki several years ago.

The last Pohokura deviation, Pohokura-3, was drilled to a total along-hole length of 7409m. All Pohokura wells were drilled into Eocene-aged sandstone reservoirs in the Kapuni Group formation.

Shell Exploration NZ said the techniques and tools used to drill that far out to sea were leading edge. The project also set world firsts for the size of the rotary steerable tools used to direct the wells.

Shell said the three-well drilling project took 14 months to complete, involved 1175 workers, most of whom were from Taranaki, and 30 companies, also mostly Taranaki-based. It took more than 300,000 man-hours.

More than 23km of hole was drilled, and more than 44km of steel pipe was used.

Meanwhile, the start of the six offshore development wells is still delayed by continuing problems associated with various technical hitches, including instability of the seabed at the well site where the jack-up Ensco Rig 56 should have started drilling in late March.

Shell Exploration NZ last week said those aspects of the project that were critical to gas delivery remained on schedule, and first gas from the 750 petajoule field was still expected later this year.