Searcher Seismic Pty Ltd is proposing to undertake the Possum three-dimensional (3D) marine seismic survey (MSS), located entirely in offshore Commonwealth waters, within the North-west Marine Region, incorporating Exploration Permits WA-436-P, WA-479-P, WA-487-P, WA-527-P and WA-540-P.

The Possum 3D MSS operational area is located ~211 km west of Broome, ~246 km north-east of Port Hedland and >180 km north of Eighty Mile Beach. The survey area is in close proximity to, but has been designed to avoid, the Mermaid Reef Commonwealth Marine Reserve boundary (4.4 km to Operational Area; 7.2km to Active Source area), the Rowley Shoals Marine Park boundary at Imperieuse Reef (11.9km to Operational Area; 21.65km to Active Source area) and the ancient coastline. Water depths across the survey area range from ~118–566m, with the deepest water depths situated in the northern half of the survey area. Seismic activities will not occur in water shallower than 100m.

• The ‘Acquisition Area’ (AA) covering ~5,400 sqkm is the focus area where the full-fold 3D seismic data will be acquired.

• The ‘Active Source Area’ (ASA) of ~8,584 sqkm includes a buffer around the Acquisition Area and is the area within which the seismic energy source may be operational, including soft start procedures and line run-outs (required to obtain full fold coverage). The full seismic source will not be operational outside of this area, although small, individual source elements may be tested during maintenance outside the ASA but still within the Operations Area.

• The ‘Operational Area’ (OA) covers ~13,447 sqkm providing an ASA ‘operational buffer’, required for activities including streamer deployment, retrieval, maintenance or recovery, routine vessel manoeuvring and other non-seismic vessel activities.

A marine seismic survey is a method of determining geological features below the sea floor, by sending sound waves into the rock layers beneath the sea floor and then recording the time is takes for each wave to bounce back as well as measuring the strength of each returning wave along a towed cable (“streamer”) of acoustic recorders. The sound wave is generated by the use of a seismic source which generates acoustic pulses by periodically discharging compressed air into the water column at regular intervals, as the vessel transits along acquisition lines within the ASA.

The Possum 3D MSS Environment Plan will be requested for validity between 1 January 2022 and end July 2023. The acquisition window is expected to be between Dec and end April, but may extend to July with additional controls implemented. The maximum expected duration of the survey with contingency time is 70 days operating 24 hours a day. This time includes shut downs for routine and reactive maintenance, repairs, transit and line turns, fauna and stakeholder avoidance. The process will continue until all survey lines, plus any re-acquisitions or ‘infill’ lines have been acquired.