The cost to develop the giant Johan Sverdrup oil field offshore Norway has improved so that it will be competitive at lower oil prices, the operator said.

Developed over a series of phases, operator Statoil said the Johan Sverdrup oil field should account for up to 25 percent of total Norwegian petroleum production once at peak capacity. Through improvements in drilling efficiency and better contracts with its suppliers, the company said the first phase of development was now 20 percent lower than initial estimates at $12 billion.

"We are strongly reducing investment costs, and we are increasing the process capacity, resource estimate and value of the field," Statoil CEO Eldar Saetre said in a statement. "Johan Sverdrup is a world-class project, and we want to create high value for the owners and society for generations."

Statoil and its partners at Johan Sverdrup, Maersk Oil and Lundin Petroleum, in early 2014 outlined the development plan for the field using multiple phases. At least half of the secondary construction contracts for Johan Sverdrup are slated for Norwegian companies.

By its latest estimate, Statoil said the project will be competitive so long as crude oil prices hold above the $30 per barrel mark. The price for Brent crude oil dropped below $30 this year, a threshold that forced some of Statoil's rivals to reconsider spending on big projects, but has since recovered to the upper $40 range.

In terms of production, Statoil said efficiency measures in part meant more was expected from the field than initially thought. Some of the final investment decisions, however, were pushed back by at least a year, though a full-field start date of 2022 remains intact.

"It has been my long held view that this world class project will continue to show improvements from a resource, cost and value perspective as time progresses," Alex Schneiter, the CEO of partner Lundin Petroleum said in a statement.

Statoil bought a minority stake in Lundin earlier this year.