OSLO (Bloomberg) — Bermuda-based Seadrill Ltd., the oil-rig company set up by billionaire John Fredriksen, rose the most in almost four months in Oslo trading after the company agreed to sell and lease back an ultra-deepwater drillship for $850 million.

The stock gained 6.7 percent, biggest gain since January 25, to a record 178.5 kroner as of 2.42 p.m. in Oslo, valuing the company at 71 billion kroner ($14 billion).

Seadrill agreed with Ship Finance International Ltd. to sell the West Polaris drillship and simultaneously lease the unit for a 15-year period, Seadrill, run from Norway, said in a statement today. Seadrill said it has six options to repurchase the unit during the charter period.

Ship Finance was in June 2004 spun off from Bermuda-based Frontline Ltd., the world's biggest operator of supertankers, which was also founded by Fredriksen.

West Polaris will remain on its balance sheet and the company won't book any gain from the sale, Seadrill said.

The drillship, which is expected to be delivered on time from a shipyard in Korea on June 30, will work for Esso Exploration Inc., a unit of Exxon Mobil Corp., for four years at a daily rental rate of $544,000 for the first three years and $602,000 for the fourth year, Seadrill said.

The arrangement with Ship Finance will, at the time of delivery, "contribute some $600 million in cash liquidity up front," Seadrill said.

If Seadrill uses similar financing for all its eight deepwater units scheduled to be delivered this year, which are all under long-term contracts, the company "will release in excess of $4 billion in cash", the company said.

This will "provide flexibility for dividend distribution as well as further growth" of the company, Seadrill chairman Fredriksen said in the statement.