Norwegian energy company Equinor has been granted environmental approval for its plan to drill an oil exploration well in the Great Australian Bight.

The National Offshore Petroleum Safety and Environmental Management Authority (NOPSEMA) says Equinor now has two of the four approvals required before activity can begin.

"The rigorous assessment process undertaken by NOPSEMA took almost eight months and involved a range of specialists with considerable environmental, scientific and engineering experience," the regulator said in a statement on Wednesday.

AAP

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

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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 400km off the South Australian coast in water depth of more than 2.2 kilometres.

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

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NOPSEMA said it had imposed stringent conditions on its approval to ensure a high level of protection to the environment, in recognition of the Bight's unique values and sensitivities.

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Restrictions include limits on the time of year any activity can take place, regular public reporting on the impact to the environment and has called for additional rigs capable of drilling relief wells to be in local waters ahead of the project's start.