Woodside Energy Ltd proposes to undertake two geotechnical surveys and one geophysical survey currently scheduled for 2016, with an option to undertake additional surveys as required throughout the life of the project.
A geotechnical survey to confirm the seabed type in the proposed Greater Western Flank Phase 2 (GWF-2) pipeline location and confirm the depth of overlaying sediment is suitable for installation of skirted foundation structures is planned for June 2016 (refer accepted Rev. 0 GWF-2 Geotechnical Investigation EP workscope).
The EP has been revised to include a small-scale geophysical survey using multi-beam echo sounder and sub-bottom profiling at selected piled MODU anchor locations (and possibly chain) to better inform the MODU piled anchor design and the associated installation method. A second geotechnical survey is also proposed for the validation of this pile installation design and will be undertaken concurrently during the project’s piling activities. An accepted Environment Plan (WEL Doc. No.: A1806AH9941349) is in place for the broader GWF-2 Tieback development which includes the piled MODU mooring installation activity.
The option for further geophysical and/ or geotechnical surveys within the Operational Area is being included within the scope of this EP resubmission. The requirement for additional surveys is unlikely, but may be identified as being necessary during detailed design of the GWF-2 Development.
Key activities of the surveys are as follows:
Geophysical sampling, including:
Multi-beam echo sounders
Side scan sonar
Sub-bottom profilers – Pinger or CHIRP; Boomer or Sparker
Geotechnical sampling, potentially including:
In situ penetration testing: - 1 – 35 metres below the seabed with a diameter up to 250 mm
Rotary core sampling: 1 – 35 m below the seabed with a typical diameter up to 85 mm
Piston / push sampling: 1 – 3 m below the seabed with a typical diameter up to 15 mm
Geotechnical seabed coring: 1 – 35 m below the seabed with a typical diameter up to 105 mm
The proposed surveys will be undertaken using vessels approximately 35 – 137 m in length.
The proposed operational area is located in production licenses WA-57-L, WA-58-L, WA-24-L , WA-5-L and WA-6-L in Commonwealth waters, approximately 135 km north-west of Dampier. Water depths in the area range from approximately 79 - 130 m.