Oil and gas explorer Advent Energy, a subsidiary of MEC Resources Ltd (ASX:MMR) said on Friday that subsequent tests on the newly-discovered natural gas resources off the New South Wales coast north of Sydney found that the reservoir could potentially yield twice the size from initial estimates.

Advent currently carries a permit to explore natural gas up to 50 kilometres from the offshore Sydney basin as the company revealed that it is concentrating its activity on an area 25 kilometres off Newcastle, where it is looking to extract gas reserves that could match the output on Bass Strait deposits.

Company executive director David Breeze said that seismic testing returned positive results and fresh technical data showed that the estimated prospective recoverable resources could prove to be a lot bigger than earlier projected.

Mr Breeze said that initial estimates of the area's gas deposits were thought to be holding 6 trillion cubic feet of gas but following the appreciation of better data, the figures were upgraded to about 13 trillion.

He said that should Advent prove to be correct and successful on the site's estimated deposits then "we could have as much gas as the Bass Strait," adding that "the Sydney Basin is a gassy basin and that could be extremely significant in terms of the capacity for the reduction of CO2 emissions."

Advent Energy has already secured a rig from the Bass Strait where it is scheduled to drill an exploratory well by the latter part of this year.