Exxon Mobil has signed an agreement to acquire Papua New Guinea-focused energy company InterOil in a deal worth over $2.5bn.

Earlier this week, Exxon Mobil placed a bid for InterOil acquisition, rivaling a takeover bid made by oil and gas firm Oil Search.

ExxonMobil said that it will offer $45 worth of its own shares for each InterOil share as well as a payment of $0.90 per million cubic feet equivalent (mcfe) for resources of more than 6.2 trillion cubic feet at the Elk-Antelope gas field, which is claimed to be one of Asia's largest undeveloped gas fields.

Exxon Mobil chairman and chief executive Rex Tillerson said: "This agreement will enable ExxonMobil to create value for the shareholders of both companies and the people of Papua New Guinea.

"InterOil's resources will enhance ExxonMobil's already successful business in Papua New Guinea and bolster the company's strong position in liquefied natural gas."

After the completion of the acquisition, ExxonMobil will gain access to InterOil's resource base, which includes interests in six licenses in Papua New Guinea covering about four million acres, including PRL 15.  

InterOil chairman Chris Finlayson, said, "Our board of directors thoroughly reviewed the ExxonMobil transaction and concluded that it delivers superior value to InterOil shareholders.  They will also benefit from their interest in ExxonMobil's diverse asset base and dividend stream."

 The transaction will be implemented by way of a court-approved plan of arrangement under the Business Corporations Act (Yukon).

It is also subject to the approval of at least 66 2/3%of the votes cast by InterOil shareholders at a special meeting expected to take place in September 2016.