Santos Offshore Pty Ltd (Santos) plans to acquire a three-dimensional (3D) marine seismic survey (MSS) in Commonwealth waters in the Bonaparte Basin.

The proposed activity is required to complete an appraisal of the carbon storage potential of Santos’ greenhouse gas assessment permit G-11-AP. The primary purpose of the 3D MSS is to facilitate future Carbon Dioxide (CO2) injection activities by providing detailed structural and amplitude imaging of the reservoir/seal interface for each identified storage target to confirm suitability for injection and storage of CO2. The Eos 3D Marine Seismic Survey (Eos 3D MSS) will be used to high grade and define future injection well locations and act as a baseline survey for possible future 4D seismic monitoring.

The survey extends into greenhouse gas assessment permit G-7-AP and overlaps petroleum permit WA-548-P, WA-27-R, NT/P88, NT/RL1, WA-454P and WA-6-R and surrounding waters in the Petrel Sub-Basin.

During the survey, a seismic survey vessel will tow a seismic source array and a series of streamers within the Operational Area, as defined in Section 2.3. The seismic source will emit pulses of low-frequency sound, which once reflected from the underlying rock layers beneath the seabed are recorded by the towed streamers. The seismic survey vessel will be assisted by other support vessels, and helicopter operations may be required in emergencies and for crew change operations.

There are two areas defined for the Activity based on the type of activities that will be undertaken and the output of the seismic source. These are the Active Source Area and the Operational Area.

The Operational Area is located approximately 107 kilometres (km) from the nearest Western Australia (WA) coastline and approximately 102 km from the nearest Northern Territory (NT) coastline. Approximate distances from the Operational Area to local towns are 192 km to Kalumburu (WA), 209 km to Wyndham (WA), 230 km to Darwin (NT) and 119 km from Wadeye (NT). Water depths in the Operational Area range between 60 and 115 metres (m) (below mean sea level). Water depths in the Active Source Area range from 67–111 m.

The survey is estimated to take up to 50 days to complete. This includes the deployment of in-sea equipment prior to the survey commencing and the recovery of in sea equipment prior to vessel demobilisation at the end of the survey. The estimated survey duration also includes provisions for potential delays caused by slow vessel speeds, extreme weather events, equipment failure or other delays caused by difficult to predict factors. Operations will be undertaken on a 24-hour basis.

Santos intends to acquire the full survey anytime from the date of EP acceptance by NOPSEMA until 31 December 2027.

The precise timing of the survey is subject to NOPSEMA’s acceptance of the EP, weather conditions, vessel availability and other operational considerations, and will take into account the seasonality of environmental sensitivities, where practicable. The exact start and end dates of the survey will be communicated to stakeholders; in accordance with the ongoing stakeholder consultation process described in Section 8.15 of the Environment Plan.