Santos Offshore Pty Ltd, propose to undertake a 3D seismic marine survey (the ‘survey’) over petroleum permit areas WA-454-P, WA-27-R and WA-40-R and surrounding waters in the Bonaparte Basin in Commonwealth waters off the Western Australia and Northern Territory coast. At its closest point, the survey Operational Area is located approximately 114 km from Kulumburu and approximately 169 km from Wyndham in WA. The survey data is required to develop regional geologic models to inform the exploration and development strategy for several petroleum permits, and the potential location of future drilling of exploration and development wells.
Revision 0 and Revision 1 of the EP sought acceptance from NOPSEMA for a survey area that included three Full-fold Acquisition Areas (Areas A, B and C). However, for Revision 2 of the EP, Santos has opted to remove Full-fold Acquisition Area C and has reduced the survey Operational Area and Active Source Zone commensurate with this change. The decision to remove Full-fold Acquisition Area C was made as part of Santos’ ongoing efforts to continue to reduce impacts and risks to ALARP and in response to concerns raised by stakeholders. Acquisition of Full-fold Acquisition Area C is no longer a priority for the survey and Santos considers it practicable to reduce the total Operational Area and to reduce potential impacts from the survey. The Operational Area has been reduced by 3,187 km2 (25%). The Revision 3 of the EP includes additional adaptive management measures for marine fauna and clarification of ESD principles in response to an opportunity to modify and resubmit the EP for Acceptance to NOPSEMA.
Seismic acquisition will be via methods and procedures similar to other seismic surveys conducted in Australian waters. The seismic survey vessel will travel along a series of pre-determined lines towing cables (known as streamers or acoustic receivers) which contain microphones (known as hydrophones). As the survey vessel travels along the lines, sound waves will be directed down through the water and into the geology below the seabed. The sound that reflects back is measured by the hydrophones and is later processed to provide information about the structure and composition of geological formations below the seabed.
Santos intends to acquire the full survey between 1 December 2021 and 31 March 2022. However, should this not be achievable, then some or all of the survey may instead be acquired the following year, between 1 December 2022 and 31 March 2023. The timing of the survey is dependent upon vessel availability, weather conditions, stakeholder consultation feedback, the receipt of the required statutory approvals and the control measures within this EP.
The survey Operational Area defines the area within which the seismic survey and support vessels will operate and is approximately 9,646 km2. Water depths across the Operational Area range from 49 meters (m) and 110 m (below mean sea level). The Full-fold Acquisition Area is the area within which the seismic source will be operated in full acquisition mode to achieve the geophysical objectives of the survey. The combined area for this zone is approximately 2,059 km2, with water depths ranging from approximately 62 m to 103 m. The Active Source Zone surrounds the Full-fold Acquisition Area and typically, this zone will be used for line run-outs, and to incrementally build the power of the seismic source from non-operation to full capacity for soft starts. This zone is approximately 5,620 km2, with water depths ranging from approximately 58 m to 105 m.
The survey is planned to be acquired over two Full-fold Acquisition Areas, Areas A and Area B, and are separate from one another, but sail lines may continue within the defined Active Source Zone, with the seismic source operating between the two Full-fold Acquisition Areas during line run-ins and run-outs. Due to this approach and the resultant improvement in operational efficiently the total survey timing has been reduced from 100 days to 60 days, with operations occurring on a 24-hour basis. An additional 5 days of contingency time within the operational area has been provided as part of the environmental assessment.
