Australian gas producer AWE Ltd. raised the reserves estimate on its flagship Waitsia gas field and said further upgrades were likely, raising the stakes for two suitors vying to take over the company.

AWE’s shares rose 1.5% on the back of the announcement, to value the company at A$511 million (US$391 million), topping the offers from Australian miner Mineral Resources Ltd and state-owned China Energy Reserve and Chemicals Group (CERCG).

AWE said on Dec. 19 Waitsia holds 820 petajoules (PJ) of proved and probable reserves, up from the previous estimate of 811 PJ as some contingent reserves have been reclassified. The estimate has been raised 80% since June after the company drilled new wells.

“During the drilling of all Waitsia appraisal wells, elevated gas shows were observed in a number of other formations... and the company is assessing whether these potentially significant resources have a development potential,” AWE said in a statement.

CERCG and Mineral Resources are both chasing AWE for a 50% stake in the Waitsia Field, which is considered Australia’s biggest onshore conventional gas find in four decades.

Based on trading Dec. 19, Mineral Resources’ all-share offer was worth A$506 million (US$388 million), well above CERCG’s all-cash offer of A$442 million (US$338 million)