A Santos spokeswoman said the spill resulted in a light sheen on the sea surface covering a small area.
“The condensate evaporated naturally within 24 hours and the impact to the environment is negligible,” she said.
Santos later found a leak in a flexible hose that connects tankers to the end of an oil pipeline from the island,she said.
According to sources who do not wish to be identified,the loading hose was lifted incorrectly several years ago causing a weakening kink that was known to Santos.
The spill occurredeight months after a 200 tonne Santos platform just off Varanus Island swung wildly out of control while it was being lifted for removal,nearly killing three workers.
Initial inquiries to Santos and regulators did not reveal the amount of oil released into the ocean. But following a further inquiry by this masthead,the Department of Transport said it was estimated to be about 25,000 litres. Santos did not dispute the figure.
Conservation Council of WA executive director Maggie Wood said the spill took place in an area highly important for marine biodiversity with vulnerable turtle populations.