About 77 pct of Songa shareholders have so far accepted deal.
Transocean, one of the world's biggest drilling rig operators, has agreed a deal to buy Norwegian competitor Songa Offshore for 9.1 billion Norwegian crowns ($1.1 bln), the two companies said on Tuesday.
The deal, which would be mostly paid for in shares and convertible bonds, would strengthen Transocean's position in offshore drilling as Songa is Norwegian oil major Statoil's largest drilling service provider.
The offer values Songa shares
at 47.50 Norwegian crowns each, a 39.7 percent premium over Monday's closing price.
Shares in Songa surged 31 percent on news of the deal, which needs the backing of at least 90 percent of Songa shareholders. So far about 77 percent of shareholders have agreed to the offer, the company said.
Songa's biggest shareholder Perestroika would become the largest shareholder in Transocean as a result of the acquisition with a stake of about 12 percent, the firms said.
"Songa Offshore is an excellent strategic fit for Transocean," Transocean Chief Executive Jeremy Thigpen said
, adding the deal would increase Transocean's order book by $4.1 billion to a total of $14.3 billion.
Including debt, the transaction sets Songa's enterprise value at 26.4 billion crowns.
Transocean said it hopes to complete its purchase of Songa, which has a fleet of seven midwater semi-submersible rigs, in the fourth quarter.
While demand for drilling has been hit by the fall in oil prices in recent years, the market for rigs able to operate in harsh-environment conditions is showing signs of recovery, Mohn said in the statement announcing the deal.
By 0808 GMT, Songa shares were up 30 percent at 44.2 crowns, their highest since March of 2016.
Reporting by Terje Solsvik