We used to have refining capacity in Australia until overregulation,environmental issues, licensing, OH&S, along with all the other hoops that must be jumped through before you can pass wind in Australia made it easier to pump our crude oil, transport it to Singapore, refine it and ship it back became the imperative.
How simple would it be for a protagonist to shut the door to shipments to and from Australia? The South China Sea is already being militarised, any thing South would be easy
to blockade, how long would Australia function in that event?
As I recall there was a synthetic fuel plant built up near Kandos in NSW during the war because we didn't have a home grown fuel production.
We ignore the lessons of history at our peril.