Otway Basin 2DMC Marine Seismic Survey

Overview

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Schlumberger Australia Pty Limited (Schlumberger) is proposing to acquire the Otway Basin 2D Multiclient Marine Seismic Survey (Otway Basin 2DMC MSS), with an estimated survey duration of 100 days which will be acquired in the period from November 2019 to June 2020. This operational window has been defined to take into account weather limitations, vessel availability and marine fauna mitigation downtime. The objective of the MSS is to identify and assist in the appraisal of potential recoverable hydrocarbon reserves in the Otway Basin.

The Operational Area is located off the coasts of South Australia, Victoria and Tasmania, outside of Coastal Waters, mostly within the Exclusive Economic Zone. More specifically, the Operational Area is located 190 km southeast of Kingscote (South Australia), 18 km south of Portland (Victoria) and 241 km northwest of Strahan (Tasmania), in water depths ranging from 50 m to 5,600 m.

The Operational Area is approximately 93,000 km2, with 95% of this area having water depths greater than 200 m. However, the proposed Otway Basin 2DMC MSS will not encompass the entire Operational Area, and this area also includes a 15 km buffer around the proposed survey lines in most cases. There are approximately 109 survey lines proposed for the Otway Basin 2DMC MSS which total up to 14,000 lineal km. Of these proposed survey lines, 98% will be in waters greater than 200 m, and 91% will be in water depths greater than 1,000 m.

The proposed Otway Basin 2DMC MSS will involve a single seismic survey vessel towing one seismic streamer up to 11 km long, at a speed of approximately 4 – 5 knots which will also have a support vessel present at all times. The survey lines will be up to 90 km long running in a northeast-southwest orientation and will have 5 km line spacing’s in most cases, where each line will take approximately 11 hours to acquire. The acoustic source selected for the Otway Basin 2DMC MSS will have an effective volume of 5,265 in3. The selection of this source represents a compromise between optimal data resolution and minimising acoustic impacts to the environment.

Schlumberger has developed an Environment Plan that details the processes involved in assessing the potential risks and impacts to the different receptors within the receiving environment and stakeholders that utilise the area. Included within this assessment are the proposed control measures and operational procedures that will be implemented in order to reduce the potential adverse environmental impacts from the planned operational activities, and risks from unplanned events, to As Low As Reasonably Practicable and to Acceptable Levels. In addition, environmental performance standards have been developed to measure the performance of the control measures and operational procedures that will be implemented throughout the Otway Basin 2DMC MSS.

Schlumberger will implement a suite of control measures to address risk to marine mammals, including the use of Marine Mammal Observers and conservative Shut-down Zones.
NOPSEMA has accepted the Environment Plan subject to a limitation that there is to be no discharge of seismic airguns in the pygmy blue whale biological important areas (BIAs) (including the Bonney Upwelling Key Ecological Feature) from 1 November 2019 to 30 April 2020, and that Schlumberger are to implement measures that limit anthropogenic noise in BIAs for the duration of the activity so that any blue whale continues to utilise the area without injury, and is not displaced from a foraging area.

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