MELBOURNE, Nov 11 (Reuters) - Woodside Petroleum said on Wednesday it would have to shut one of the five trains, or processing units, at the North West Shelf LNG plant in Australia as early as 2024 if no third party gas supply agreement is reached.

North West Shelf LNG, operated by Woodside, is Australia's oldest and largest LNG project with a capacity of 16.9 million tonnes a year.

The project's owners are aiming to line up deals with other resource owners (ORO) by the end of 2020 to supply gas as the project's original fields dry up.

"In the event that early ORO does not transpire, in that scenario, then we will be looking to shut down trains. And the first train that will shut down is likely to be a smaller train, likely LNG 3, and that will be in as early as 2024," Woodside Senior Vice President Fiona Hick told investors in an online briefing. (Reporting by Sonali Paul; Editing by Jacqueline Wong)