Norwegian oil company Equinor wants to start drilling at a depth of almost 2.5km by the end of 2020 in the Great Australian Bight. 

The company still needs approval from the National Offshore Petroleum Safety and Environmental Management Authority (NOPSEMA).

A leaked environmental plan by Equinor shows a "worst credible case discharge scenario".

The document was obtained by Greenpeace.

Maps in the plan show coastal areas that could potentially be impacted from Albany in Western Australia to Port Macquarie on the NSW Mid North Coast.  

Greenpeace said it was the first time modelling had shown an oil spill could reach so far.

Climate Change Australia Hastings spokesperson Harry Creamer said  it was "disturbing an operation so far away could reach Port Macquarie."

"We value our beaches highly, they are among the best in the world and we need to protect them," he said. 

Mr Creamer said while they might only be a small likelihood of a well failure the consequences would be far reaching.

He cited the devastating consequences of the oil spill in the Gulf of Mexico in 2010 by the BP operated Macondo Prospect.

Nathaniel Pelle from  Greenpeace Australia Pacific said "lasting damage could be inflicted on Port Macquarie Beaches."

" The modeling obtained by Greenpeace Australia Pacific shows that greater than 1 gram of oil per square meter could wash up on Central NSW beaches including Port Macquarie," Mr Pelle said.

"That oil could stay on beaches and local reefs for months or even years in places that are hard to clean up like inaccessible beaches and cliffs."

 Equinor has since  released an official environmental plan and insists that drilling could be carried out safely. 

"Equinor has implemented strict barriers to prevent a spill, [prepared] intervention and mitigation measures as backup and is confident that the risk has been reduced," the report stated.

Jone Stangeland, Equinor's country manager for Australia said this was the first time a draft Environment Plan for an offshore exploration well has been published for public comment.

"For Equinor, any oil spill is unacceptable, which is why we plan meticulously to ensure we can drill safely and this is demonstrated in our draft EP," Mr Stangeland said.

"We have drilled thousands of offshore wells over the years, and we have never had any incidents leading to pollution of the shoreline.

"It is also important to note that this area is open for oil and gas exploration and that 13 other exploration wells have already been drilled safely in the Great Australian Bight.

"As part of the regulated risk assessment process, NOPSEMA requires all Environment Plans to provide modelling for the impacts of simulated, unmitigated oil spills to make sure we have planned for anything that could possibly happen, regardless of how unlikely it is.

"We are required to form a single map that superimposes 100 different simulations of a worst-case oil spill under varying weather conditions.

"The modelling assumes that every piece of safety equipment on the rig fails, and nothing is done to stop the leak, contain or disperse the oil for a 100 days.

"This would never happen in reality...In the unlikely event of an actual oil spill, we would respond immediately. And of course, 100 different events cannot occur simultaneously."

Equinor’s environment plan is up for public comment until the 20th of March 2019. For more details click here.