OSLO (Bloomberg) ? Bermuda-based SeaDrill Ltd. yesterday offered to buy Smedvig ASA, Norway?s largest rig owner, for 15.6 billion kroner ($2.4 billion), challenging Noble Corp. for control of the company as demand escalates for drilling.

SeaDrill, owned by Norwegian billionaire John Fredriksen, bid 205 kroner per Class A share in Smedvig and 165 kroner for the non-voting Class B shares, the company said in a statement to the Oslo exchange today. Class A shares in Smedvig rose as high as a record 209.5 kroner in Oslo from 200 kroner last week, indicating some investors expect a higher proposal.

Surging oil and gas prices have prompted companies including BP Plc to step up the search for new deposits, causing lease rates for drilling rigs and orders for new rigs to climb. Noble, the world?s second-largest offshore driller, bought 29 percent of Smedvig last month and said it might try to acquire the rest.

?A combination of SeaDrill and Smedvig seems a pretty sensible idea from an industrial point of view,? said Kristian Falnes, who helps oversee about $4.3 billion in stocks at Stavanger Fondsforvaltning in Stavanger, Norway, including SeaDrill and Smedvig B shares. ?That the shares trade above the offer price indicates some think Noble might make an offer.?

Stavanger Fondsforvaltning has given a conditional acceptance of the current bid, he said.

Fredriksen, 61, built his fortune in the oil-tanker industry, where he has expanded Bermuda-based Frontline Ltd. into the largest in the business by capacity through mergers and acquisitions. He is Norway?s richest individual, with assets worth 33.3 billion kroner.

Fredriksen is trying to replicate Frontline in the drilling industry. Acquisitions last year included Odfjell Invest Ltd., which has rigs under construction in Singapore, and 32.3 percent of Indonesia?s PT Apexindo Pratama Duta, which will help market SeaDrill?s rigs in the Middle East and Asia.

SeaDrill, which operates out of Oslo, already controls 37 percent of Smedvig?s stock. Last week, it bid 201 kroner for the company?s Class A shares, a proposal that was abandoned after failing to win enough support from Smedvig shareholders. The new plan requires 50 percent acceptance to go through.

?SeaDrill has reacted to strong encouragement from many of the larger Smedvig shareholders to create a sound industrial platform through combining the two companies,? Fredriksen said in the statement. ?We have also noted the support expressed from Smedvig management for such a transaction.?

After raising the price, SeaDrill has received acceptances for about 19.3 million Class A shares and 8.9 million Class B shares, the company said. Including shares it already owned, SeaDrill controls 37 percent of the capital and more than 40 percent of the votes in Smedvig, it said.

Investors that pledged to sell to SeaDrill include Norway?s government pension fund, Smedvig?s second-largest owner after Noble with 9.9 percent of the capital.

Noble became Smedvig?s biggest owner last month, when the Sugar Land, Texas-based company bought its stake from the company?s chairman, Peter Smedvig. Noble paid 200 kroner each for the Class A shares and 150 kroner for the Class B shares.