Disrupt Burrup Hub campaigner Trent Steven Rojahn, 35, pleaded guilty on Wednesday in Perth Magistrates Court to one count of criminal damage and destruction of property.
He was ordered to pay Woodside $9,167.13 and fined $300, with a spent conviction, for the incident in February 2023.
Rojahn used a fire extinguisher and spray cans to paint the slogan "Disrupt Burrup Hub" across a window at the entrance of the building in Perth, according to the group, in opposition to a gas project in WA's northwest.
Woodside in December launched legal action against three other Disrupt Burrup Hub campaigners.
It's understood to be over the alleged release of a stench gas bomb in the same Woodside building in June 2023 that forced the company to evacuate thousands of workers.
A letter sent by the company's lawyers to one of the protesters after the incident said Woodside had suffered loss and damage.
It requested she supply information about other people involved and any documents relating to the planning, preparation and execution of the incident.
The Burrup Hub development is an expansion of the existing Pluto gas plant to process gas from the Scarborough offshore gas field.
Disrupt Burrup Hub claims the project could produce billion of tonnes of greenhouse gases.
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