FDM is currently in Administration, not Receivership or...

FDM is currently in Administration, not Receivership or Liquidation. So my understanding - which could be wrong in some of the details, though not, I think, the conclusions - is that at present, shareholders are in limbo and cannot write off their investment. This is because,technically, Freedom could still be revived. If the oil price shot up to $60-70 this would be a possibility, but is highly improbable.
If, or rather when, it goes into receivership, the Receiver will conduct an audit, discover that the Company is insolvent, decide who has first, second (and so on) claim on the assets, announce that the bank will be repaid, Ramas might receive a portion of their claim and the shareholders will get $0.00.
Once that is in writing (and you can keep track on the deListed Australia website), then you can claim against tax*.
There may be a complication in that Freedom has an operating company which holds the leases and which I presume is registered in the US. There might be a possibility that it could seek Chapter 11, which would freeze the whole process. But even if this is a possibility, it would probably not save FDM, which is Australian registered and subject to Oz law.

* Provided the investment isn't in your SMSF and it is in Pension mode, in which case it's Tough Titties.