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Geotechnical and Geophysical Investigations

The CarbonNet Project is planning for its next field activity, the drilling of an offshore appraisal well (OAW) at the Pelican site in Commonwealth waters in late 2019.

Prior to drilling the OAW, standard geophysical and geotechnical investigations will be undertaken to confirm that the proposed location is suitable to support a drill rig.

Investigation Methods and Equipment 

Geophysical investigations involve seabed imaging, assessing water depths, profiling underwater topography and identifying seabed obstructions (such as unmarked shipwrecks and buried pipelines). The investigations are likely to be conducted using a small, locally-based vessel.

Geotechnical investigations involve taking shallow cores of seabed sediment and underlying rock to establish geological conditions at potential drill rig locations. Geotechnical investigations are performed using a medium sized vessel capable of transporting and deploying the larger equipment required for this task.

All work will take place in Commonwealth waters with both activities expected to take less than one week each to complete. The impacts of these activities are expected to be minimal, temporary and localised.

The investigations are being managed by AGR (Australia) Pty Ltd as the Drilling Management Contractor for CarbonNet. AGR has drilled over 40 offshore wells in Australia.

An Environment Plan is being prepared to address the potential impacts of these investigations which will be submitted to the regulator (National Offshore Petroleum Safety and Environmental Management Authority) for approval.

Table 1 describes the investigation methods.

Geophysical investigations (Figure 1) – Commonwealth waters

Equipment Purpose Duration Potential impact and mitigation
Multi-beam echo sounder (MBES) Undertakes detailed measurements of water depth (bathymetry) in the project area. About 4 days

Potential minor and temporary impacts on sound sensitive fauna, if present. To be risk assessed in Environment Plan, informed by habitat assessments.

In accordance with the EPBC Act Policy Statement 3.1, a 500-m shutdown zone will be maintained during equipment operation minimise impacts.

Side-scan sonar Detects hazards such as existing pipelines, lost shipping containers, boulders, debris, unmarked wrecks, reefs and craters. Operated at the same time as the MBES As above
Sub-bottom profiler Investigates the layering and thickness of the uppermost seabed sediments, typically imaging to a minimum depth of 30 m below the seabed. Operated at the same time as the MBES As above
Shallow seismic Provides near-surface geological structural information and detects geohazards. Around 24 hours at less than 5% intensity of that used for the marine seismic survey. As above
Magnetometer Detects metallic objects on or immediately below the seabed (e.g., shipwreck debris, anchors etc) that may not be identified by acoustic means. Operated at the same time as the MBES The source will be kept to the lowest level required.  Potential impacts to be risk assessed in Environment Plan. 

Picture showing a boat and types of geophysical equipment including a multi-beam echo sounder, side-scan sonar, sub-bottom profiler, shallow seismic and magnetometer.

Figure 1: Geophysical investigation equipment.  

Geotechnical investigations (Figure 2) - Commonwealth waters

Equipment Purpose Duration Impact
Seabed grab sampling (SGS) Provides samples of unconsolidated sediments e.g., sands, silts and clays for analysis. A few hours in total Temporary and localised seabed disturbance and turbidity. Impacts to be risk assessed in Environment Plan, informed by habitat assessments.
Seabed coring (SC) Provides samples for geophysical analysis of formations below the seabed. 5 - 7 days As above
Piezo Cone Penetrometer Test (PCPT) Determines soil strength and helps to delineate soil stratigraphy.  Takes place at same time as coring ops. As above

Note: The above information is preliminary as of July 2018.

Picture showing a boat and types of geotechnical equipment including seabed grab sampling, seabed coring and piezo cone penetrometer test.

Figure 2: Geotechnical investigation equipment. 

Location

The investigations will be carried out in Commonwealth waters approximately 6 km to 11 km offshore between late 2018 and the first half of 2019 (Figure 3). Exact scheduling and duration is dependent on the timing of regulatory approvals, fair sea state conditions and availability of suitable vessels.

Figure 3: Location map, CarbonNet Geophysical and Geotechnical Investigation Area. 

Image of Bass Strait offshore from Golden Beach and Paradise Beach Victoria showing the location of the CarbonNet Project geophysical and geotechnical investigations. The investigations will be in Commonwealth waters.

Timeframe

The investigations will occur between late 2018 and early 2019.

More information and feedback

For more information, download the CarbonNet Geophysical and Geotechnical Investigation SheetCarbonNet-Geophysical-and-Geotechnical-Investigations-Information-Sheet.docx (DOCX 466.72 KB)DOCX icon

If you have any feedback or questions about the geotechnical and geophysical investigations please contact AGR:

Phone: 1800 312 966

Email: carbonnet.drilling@agr.com

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