A worker was "nearly killed" and an accommodation vessel carrying 270 workers was left with two holes in its hull after a serious safety incident at Chevron's Gorgon project off Barrow Island.
The Department of Transport is investigating the incident, which happened about 7am on Tuesday, amid maritime union claims that hundreds of lives were put at risk.
It is understood the MS Finnmarken, which is registered to Norwegian passenger and freight company Hurtigruten, was struck repeatedly by a barge during strong winds.
Maritime Union of Australia organiser Noel Neilson said a fender on the mooring barge had failed, leaving its exposed steel deck to batter the Finnmarken's hull at least a dozen times amid the winds measured at 52-54km/h by the Bureau of Meterology.
"(The barge) was ringing the ship like a bell," he said.
Union sources claim a worker standing on the barge was nearly killed when the Finnmarken's line broke. The worker was forced to hit the deck as the heavy duty rope whipped past him.
The captain tried to move the vessel off the mooring but collided with it in the process, puncturing holes in its hull 1m above the water line.
The captain then sailed the holed vessel for Dampier, a move the union says risked hundreds of lives.
"He should have notified the authorities and assessed the damage before he sailed," a second union source familiar with the incident said.
It was not until the following day at Dampier the holes were discovered in the vessel's hull.
Neither Finnmarken or Chevron's maritime contractor Boskalis could be reached for comment.
A spokesman for Chevron did not contradict the union's version of events.
In a written statement in response to questions, it said a hole was discovered in the hull "during a visit to Dampier Port for operational reasons".
The statement said at "no stage was the safety of the ship at risk" but the spokesman could not comment on whether lives of workers were at risk.