OSLO - Norwegian oil firm Det norske said on Wednesday it would appeal a government decision giving it a smaller stake in the giant Johan Sverdrup oilfield than it wanted, and reported second-quarter operating earnings below expectations. Det norske had argued that it should have a larger share in the field than the 11.89 percent proposed by operator Statoil in February. But a decision by the Ministry of Petroleum and Energy has since cut it to 11.57 percent.. Sverdrup, Europe’s costliest offshore energy project, contains up to 3 billion barrels of oil equivalent (boe) and could operate for 50 years. Det norske, controlled by billionaire Kjell Inge Roekke’s Aker, said it has decided to appeal the ministry decision to the government. “For Det norske, it is a decisive principle that the ownership interests in Johan Sverdrup are to be distributed according to a combination of volume and value. We do not see this principle reflected in The Ministry of Petroleum & Energy decision on the unitization split,” Chief Executive Karl Johnny Hersvik said in a statement. The field, also owned by Lundin Petroleum, Maersk and state holding firm Petoro, is forecast to start production by the end of 2019. Det norske has earlier said it was keeping all possibilities open, including taking legal action. Det norske reported an earnings before interest and tax (EBIT) of $122 million for the quarter, below expectations for $131 million and $20 million in the same period a year ago. A comparison with earnings figures a year earlier is skewed because Det norske has since acquired Marathon Oil’s Norwegian business, significantly increasing its production and revenue. The firm reiterated its 2015 production forecast of between 58,000 and 63,000 barrels of oil equivalent per day.