The Offshore Petroleum and Greenhouse Gas Storage Act requires holders of oil and gas titles in Australian Commonwealth waters to remove all structures and equipment in connection with offshore petroleum operations at the end of production.
While this requirement appears to mandate a complete removal of all equipment, it is subject to other provisions of the Act which enable the possibility of partial removal or even abandonment in situ; to this end the titleholder may make alternative arrangements for the treatment of equipment in an environment plan (EP), provided that those arrangements ensure that impacts and risk are acceptable and reduced to as low as reasonably practicable (ALARP).
This flexibility enables the titleholder to potentially propose an alternative approach if other potential consequences, such as excessive cost or safety risk, or even different kinds of environmental impact and risk, show that removal may not necessarily be the best option. Such flexibility is in contrast to other mature oil and gas regions such as the North Sea, where total removal is the norm due to long standing legal obligations which don’t apply in Australia.
In a recent study into decommissioning options for subsea infrastructure by S2V Consulting with an Australian offshore operator, the underwater cutting, lifting, transportation (offshore and onshore) and ultimate onshore treatment and disposal of equipment was found to introduce significant safety risks (e.g. heavy lifts, increased vessel time, worker exposure to offshore occupational risks) and environmental impacts (e.g. greenhouse gas emissions from transport) that outweighed the impact of leaving contaminant-free equipment in situ. Furthermore, it was determined that ecological value would be adversely impacted if subsea equipment was removed, due to the loss of habitat that had become established during the operational period of the facility. Significantly, the potential cost differential between removal versus in-situ abandonment was in the order of 90% (equating to tens of $millions).
With comprehensive supporting information, a multi-discipline team (environment, subsea, safety etc), and the use of techniques such as net environmental benefit analysis (NEBA) – already familiar to operators in the preparation of oil pollution emergency plans – operators can demonstrate that their approaches and preferred options are ALARP, and if sound arguments are put forward, the regulator (NOPSEMA) must accept this. Of course, in addition to objective scientific factors, ‘acceptability’ to stakeholders of alternative approaches is key, and the power of public / stakeholder perception in influencing (and potentially overturning) supported scientific arguments is well documented in instances such as the decommissioning of the Brent Spar (North Sea). Therefore, an effective stakeholder identification and consultation programme is also essential to determining an acceptable option and achieving a smooth approvals process.
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