Santos files plan for new seismic survey offshore Australia

Australia’s Santos has submitted an environment plan for the Keraudren Extension 3D Marine Seismic Survey located offshore Australia and the plan is now open for comment. 

According to an update by Australia’s offshore regulator NOPSEMA, Santos proposed to undertake a 3D seismic marine survey over a portion of exploration permit areas WA-435-P, WA-436-P, WA-437-P, and WA-438-P, and surrounding waters in the Bedout Sub-basin in Commonwealth waters off the coast of Western Australia.

At its closest point, the survey Operational Area is located approximately 45 kilometers (km) from the nearest land (Bedout Island), 56 km from the nearest mainland coastline and 141 km from the nearest regional town Port Hedland.

The survey data is required to develop regional geologic models to inform the exploration permit retention strategy, and the potential location of future drilling of exploration and development wells.

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, which contain microphones. 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.

The survey may be acquired in stages. The exact area to be acquired in each stage will be determined based on operational and timing factors, and in consultation with key stakeholders. To allow for flexibility a period of three years, between 2020 to 2022, is proposed in which to complete the survey. It is Santos’ intention to start the survey in 2020 and to acquire the full survey within two of the three years.

In order to avoid sensitive fish spawning and whale migration periods, the acquisition of the survey will only be undertaken between February 1 to July 31 in any given year. The first phase of acquisition is unlikely to start before April 2020.

The survey will take at least 132 days to complete, with operations occurring on a 24-hour basis. An additional 30 days of contingency time within the operational area has been provided as part of the environmental assessment.

The survey Operational Area defines the area within which the seismic survey and support vessels will operate and is approximately 20,160 km2. Water depths across the Operational Area range from about 40 m to 250 m.

The Survey Area is comprised of the Ramp-up Zone and Full Power Zone. The Full Power Zone is the area within which the seismic source will be operated in full acquisition mode to achieve the geophysical objectives of the survey. This zone is approximately 8,620 km2, with water depths ranging from 40 m to 168 m.

The Ramp-up Zone is a zone that surrounds the full power zone. Typically, this zone will be used to incrementally build the power of the seismic source from non-operation to full capacity, for the purpose of soft starts. This zone is approximately 2,610 km2, with water depths ranging from about 40 m to 185 m.

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