The drilling program by Norwegian energy group Equinor is a step closer after the company was granted approval for its environmental plan.

The decision from the National Offshore Petroleum Safety and Environmental Management Authority (NOPSEMA) has been welcomed by the South Australian and federal governments and the energy sector.

But the Wilderness Society and Greenpeace say they will continue to fight the proposal.

"The approval flies in the face of experts, communities, traditional owners, surfers, coastal families, and the South Australian seafood industry, who have all relentlessly campaigned against plans to drill for oil in the Great Australian Bight for over five years," Greenpeace Australia spokesman Jamie Hanson said.

The Wilderness Society said it was considering legal options to stop the well from going ahead.

"The fight for the Bight is one of the biggest environmental protests Australia has seen, and this approval will only further mobilise community opposition," director Peter Owen said.

Equinor was first granted a petroleum title over areas in the Bight in 2011 and now has an accepted environment plan.

It must still have a well operations plan and a facility safety case approved before it can begin drilling its proposed Stromlo-1 well at a site about 400 kilometres off the SA coast in water more than 2.2km deep.

If approved, Equinor plans to begin work in late 2020 with the operations expected to last for 60 days.

Federal Resources Minister Matt Canavan said the Bight project had the potential to open up a major new petroleum basin.

"In a continent as large as ours I hope we can find another oil and gas province to replace the Bass Strait," he said.

Equinor's country manager for Australia, Jone Stangeland, said environmental approval was an important milestone for the drilling program.

"We have been preparing for safe operations for two and a half years, holding over 400 meetings with more than 200 organisations across Southern Australia," he said.

Australian Associated Press