Viva said a failure of a contractor crane at the facility in Victoria had caused a compressor to be dropped to the ground.
An exclusion zone was put in place, and no one was injured.
OIL refiner and fuel retailer Viva Energy was trading down 3.9% on Wednesday after advising shareholders of an incident at its Geelong refinery which will hit earnings.
Viva said a failure of a contractor crane at the facility in Victoria had caused a compressor to be dropped to the ground.
An exclusion zone was put in place, and no one was injured.