Swedish oil firm Lundin Petroleum plans to start oil production at its Edvard Grieg field offshore Norway on schedule in the fourth quarter of this year, and the field could have more resources than previously estimated, it said on Thursday.

"The field is still on track to produce first oil in the fourth quarter," Lundin Chief Executive Ashley Heppenstall told an energy conference.

"There is upside potential in the field, but we will know that better after we finish appraisal drilling this summer," he added.

Lundin Petroleum has a 50 percent stake in the field, which is estimated to hold 187 million barrels of oil equivalent while Wintershall and Statoil each have 15 percent and OMV has 20 percent.