The case against oil giant Shell and Austrian explorer OMV is underway at the High Court in Wellington.
Todd Energy alleges its joint venture partners have colluded to constrain production at the Pohokura gas field, near Taranaki, since 2006.
It says the field was limited to 70 petajoules of gas annually, when it could have produced 86 petajoules.
The privately owned company, which has a 26% stake in the field, says under the joint agreement it had the right to sell its share of the total production capable of delivery at any given time.
It has alleged the actions of Shell and OMV breached the Crown Minerals Act and the Commerce Act, and had the likely affect of controlling or maintaining the price of gas, and lessening competition in the gas market.
Todd Energy is seeking damages of $274 million.
The case is set down for at least seven weeks.
Economist lay member Professor Martin Richardson is sitting with Justice Robert Dobson during the case.
