The National Offshore Petroleum Safety and Environmental Management Authority this morning published a direction ordering Eni Australia to clean up its now defunct oil field, warning that a piece of infrastructure floating in the field posed a serious risk to well integrity. 

The piece of infrastructure floating is suspected to be a mid-depth buoy weighing 40 tonnes, which is tied back to other infrastructure. 

 The mid-depth buoy has floated to the surface and could drag subsea infrastructure with it, putting at risk the intergrity of the Woollybutt field production wells. 

It appears that the buoy, which is supposed to be 50 metres underwater, has come loose. Energy News understands the buoy mooring chains corroded away. 

The buoy supports oil production pipelines which are tied back to production wells. 

The regulator said the buoy remained tied to subsea wells and lines and that it "posed a threat to the safety of vessels in the area" as well as putting wellhead integrity at risk. The buoy is approximately 10 metres in diameter. 

Should the buoy pull infrastructure apart it could lead to an oil spill or drift away from the operational area. 

It is the first direction Eni Australia has received over the concerns, although NOPSEMA issued the company an improvement notice back in May.

Eni Australia claims that the buoy is being monitored. 

The Woollybutt field ceased production in 2012 and Eni has applied to decommission the field. This is expected to occur in 2021.

Under the direction from NOPSEMA, the company will need to "take all reasonable measures" to mitigate the risk of the buoy floating away and dragging with it subsea infrastructure. 

It must also assess the condition of the equipment and subsea wells to ensure the integrity.