Adelaide-based Santos said that XRG, comprised of the Abu Dhabi National Oil Company, Abu Dhabi Development Holding Company and US private equity fund Carlyle, had tabled an indicative cash offer of US$5.76 a share — equivalent to A$8.89 — which represented a 28 per cent premium to the company’s closing share price last week.

Santos shares surged over 15% following a $18.7 billion takeover bid by a consortium led by a unit of Abu Dhabi's National Oil Company. The consortium also includes the Abu Dhabi Development Holding Co and global private equity firm Carlyle Group.

But the offer for the ASX’s second-largest oil and gas producer has been met with a lukewarm reception from investors, who say the price could be higher.