Santos is close to finalising a deal with energy giant ExxonMobil Corporation to acquire a stake in the P'nyang gas field in Papua New Guinea, as the joint venture partners eye a lucrative expansion of the $US19 billion PNG LNG venture. The Adelaide-based oil and gas producer is understood to have concluded talks with Exxon, the operator of PNG LNG, over taking a 10 per cent to 15 per cent stake in the field alongside partners Exxon, Oil Search and JX Nippon, according to sources close to the deal.