The relevant act is the federal Offshore Petroleum and Greenhouse Gas Storage Act 2006 (which includes amendments up to 2021). Below are two links to this act:
We start with section 400 about long term liability. You can see all sorts of liabilities being indemnified by the federal government, even during the closure assurance period. The indefinite indemnity for long term liability is described in (1)(d)(iii).
| 400 | Indemnity - long-term liability | |||
| Scope | ||||
| (1) | This section applies if: | |||
| (a) | a site closing certificate is in force in relation to an identified greenhouse gas storage formation; and | |||
| (b) | when the application for the certificate was made, the formation was specified in a greenhouse gas injection licence; and | |||
| (c) | there is a closure assurance period in relation to the formation; and | |||
| (d) | the following conditions are satisfied in relation to a liability of an existing person who is or has been the registered holder of the licence (whether or not the licence is in force): | |||
| (i) | the liability is a liability for damages; | |||
| (ii) | the liability is attributable to an act done or omitted to be done in the carrying out of operations authorised by the licence in relation to the formation; | |||
| (iii) | the liability is incurred or accrued after the end of the closure assurance period in relation to the formation; | |||
| (iv) | such other conditions (if any) as are specified in the regulations. | |||
| Indemnity | ||||
| (2) | The Commonwealth must indemnify the person against the liability. | |||
The site closing certificate is issued after injecting of greenhouse gases into a site has ended, as described in section 392. That section does not say much. The real conditions for getting to this point are described in section 388 in the conditions for the pre-certification notice. I am not going to copy the whole section here. But what the responsible minister must have regard to and what can create a condition where the minister may refuse the notice are a "significant risk" of "significant adverse impact" on various things. There is a quadruple fudge:
There is also mention of greenhouse gases not behaving as described in "Part A of the Approved Site Plan" Approved Site Plans are described in section 457 and there is no reference to Part A or the requirements on greenhouse gas behaviour. But in any case, this deals with behaviour at the time of site closure not long-term considerations.
The closure assurance period is described in section 399. It will end on the "decision day" which is "at least 15 years" after the issue of the site closing certificate. The conditions are similar. There is the same reference to the "Part A of the approved site plan" and the minister "is satisfied" that there is "no significant risk" of "significant adverse impact" on various matters including the environment with no explicit mention of leakage.
Leakage does get mentioned in Section 379, mostly in the context of current leakage. But it does describe as a "serious situation" if "there is a significant risk that a greenhouse gas substance injected into the identified greenhouse gas storage formation will leak from the identified greenhouse gas storage formation" Section 380 then describes what the minister may do "If the responsible Commonwealth Minister is satisfied that a serious situation exists in relation to an identified greenhouse gas storage formation specified in a greenhouse gas injection licence". That's a tough test, though, because it puts the onus on the minister to determine that a serious situation exists. And there is no obligation on the minister to do anything about it.