Energy News understands Inpex has shut down its infill drilling operations on the Maersk Deliverer drill rig on the Ichthys gas field after large pipes fell onto the drill floor and then overboard while being lowered into place. 

The pipes, called risers, weighed 23-tonnes each and if they had fallen on someone would have killed them. Risers provide a connection from the well head blowout preventer to the rig and transport hydrocarbons and mud during drilling. They are different from drilling pipes. 

It is the most serious safety near-miss to occur over recent months and is classed as a "high potential" incident. 

Sources speaking to Energy News said the entire Maersk rig shook when the pipes landed. 

"It is a miracle no one died," a source said, "It was lucky [the risers] didn't punch hole (sic) in the rig." 

It is unknown at this stage what equipment failed or what cause is behind the incident. 

The National Offshore Petroleum Safety and Environmental Management Authority (NOPSEMA) launched an inquiry over the weekend. 

NOPSEMA inspectors flew to the rig on Saturday to survey the damage and returned on Monday. 

The Maersk rig was drilling infill wells for Inpex's phase two development of the Ichthys wet gas field in production licence WA-50-L in the Browse Basin.

The campaign includes 15 new production wells and aims to boost condensate production for export to Japan and gas for processing at the Ichthys LNG onshore plant in Darwin. 

The regulator is yet to issue a direction, improvement notice or prohibition order to Inpex or Maersk.