The Environmental Protection Agency has proposed that the €900m Corrib gas onshore terminal in Co Mayo be granted a licence.
The announcement constitutes a significant advance for the controversial project.
RTÉ News has learned the agency believes 85 separate conditions should apply, but will delay a final decision in case an oral hearing is deemed necessary.
Speaking on RTÉ Radio's Morning Ireland, Mark Garavan of the Shell to Sea campaign said he was surprised, but not shocked at the announcement.
He said the General Election could provide opportunities to reverse it.
Shell E & P Ireland wants to build a refinery and combustion plant at Bellanaboy in Mayo which can process 9.9m cubic metres of gas per day.
The company applied for what is called an integrated pollution prevention and control licence from the EPA in December 2004.
The agency sought additional information last year relating to the possible risk of environmental pollution, a request Shell said was normal.
However opponents in Shell to Sea contended essential information was being withheld by the company.
But today the EPA has said it is satisfied that emissions from a licensed refinery would not adversely affect human health or the environment.
Objectors now have 28 days to apply for an oral hearing into the matter.
The final decision on whether to grant a licence will be taken by the board of the EPA.
