The New Zealand Supreme Court has refused Shell's application for leave to appeal to that court following last December's Court of Appeal ruling that the status quo should be maintained, with current operator Shell Todd Oil Services (STOS) continuing to run the field.

STOS, an unincorporated organisation jointly owned by Shell NZ and Todd Energy, operates the offshore Maui and onshore Kapuni gas-condensate fields but holds no equity in either licence.

"The Supreme Court's decision is a comprehensive victory for Todd Energy and I am very pleased that this long-running saga is now at an end," Todd Energy managing director Richard Tweedie said.

"The uncertainty that Shell's attempted takeover has generated for the field owners and for STOS staff is over."

Tweedie told PetroleumNews.net from Wellington this morning that all STOS staff, about 350 people in Taranaki, should feel more secure in their jobs now that this long-running courtroom saga had finally been concluded.

He said the legal dispute began in April 2005 when Todd Energy was forced to obtain a High Court injunction to stop Shell forcing STOS' resignation as Maui operator.

Shell had - at an earlier STOS board meeting - tried to use its casting vote on the board to remove STOS as operator and replace it with a Shell subsidiary.

Tweedie said this matter had now been before five courts and 10 judges. It had been before the High Court and Court of Appeal twice each and the Supreme Court once.

"All have found in favour of Todd Energy and Shell's proposal to have STOS resign was found to be a breach of the Maui joint venture arrangements," he said.

"It was also a breach of separate joint venture arrangements between Shell and Todd, entered into in 1955 and renewed in 2002, a core component of which is having field services provided by STOS."

Last year Shell won a similar court case, which Todd also opposed, enabling it to remove STOS as Pohokura operator and gain control of that near-shore Taranaki gas field.

Tweedie said the courts found the real reasons Shell sought to make changes were to give it greater control over fields it had stakes in and to maximise their value in the event that Shell decided to sell its New Zealand upstream businesses.

Documents produced during the high court squabble revealed Shell feared a $US100 million ($A112 million) loss in the value of its New Zealand oil and gas assets if it did not take the operator's role at its major Taranaki fields, Maui and Pohokura, and that it wanted to re-organise its New Zealand operations in preparation for a possible sale.

Shell NZ spokeswoman Jackie Maitland said the company was disappointed with the Supreme Court decision but it would continue to be business as usual for Shell and for STOS.

The Maui partners are Shell Exploration NZ (83.75%), Todd Energy (6.25%) and Austrian firm OMV (10%).

The Pohokura partners are operator Shell Exploration NZ (48%), Todd Energy (26%) and OMV (26%).