The hearing is before Justice Ellis and is expected to last two days.
However, a judicial ruling on the Methanex case - which calls for a temporary halt to the critical re-examination and re-allocation of the remaining Maui reserves - is unlikely before the end of next week.
Asia-Pacific vice-president Bruce Aitken said he was pleased the Methanex application for an injunction had been given urgency by the court. He has earlier said the hearing would be held in chambers and that Methanex would abide by any ruling.
The other two big Maui gas users - Natural Gas Corporation and Contact Energy - had requested to be party to the high court proceedings. Treasury officials, representing the government, were also expected to be present.
The affected parties - from the Maui mining companies, Shell NZ and Todd Energy to the three end users - will eagerly await the judicial ruling, which could set the tone for whether industry will or won't successfully work together for years to come.
The redetermination of the remaining Maui reserves - essentially who gets what scraps from the faltering field - is shaping up to be the largest and most important fight in the New Zealand industry for years.
A negative outcome for Methanex will see it progressively close its Taranaki methanol plants - a move which would cost Taranaki and the country over $40 million a year in lost earnings and more than 200 jobs.
Commentators say there are still out-of-court solutions possible, though the longer the dispute drags on, the less likely that is to happen.
If the judge's ruling is favourable to Methanex, any of the other parties could appeal, which would open the door to counter-appeals all the way to the London-based Privy Council.
Natural Gas Corporation and Contact Energy can survive losing physical gas and rights to pre-paid gas, NGC less so than Contact, through any downward revision of remaining Maui reserves. However, losing physical gas will put Methanex out of business.
Complicating the whole issue is the intent of contract law written over two decades ago and that the government contracts with the three users do not exactly mirror those between it and field owner Maui Development.
Some commentators also say now is the time for the government to stop pocketing the Energy Resources Levy (of NZ45c per Gigajoule) it collects from the users, and use that money to help oil companies develop other smaller fields.
"They should have been doing this years ago, as the Dutch government does with the Gronigin field, saving the big field so there is about ten years of life left, and using smaller fields. It's a bit late now though, for the New Zealand government to try anything like this," said one commentator.
