Pre-Piling Template Monitoring, France
Imenco were approached to provide subsea acoustic communication in support of survey measurements for a drilling and pile installation campaign for an offshore wind farm in northern France.
Operations were to involve a template with three sleeves, allowing three temporary casings to be drilled into bedrock, followed by installation and grouting of pin piles.
Key to successful installation and grouting of piles was accurate and reliable measurement of the progress of these temporary casings. This was used to verify drill depth and ensure sufficient grout pumped between pin piles and bedrock whilst removing temporary casings reducing risk of voids.
Description of solution:
NASNet® equipment with Acoustic Digital Spread Spectrum communication was selected as one of the most robust through water communications systems in the market. The equipment spread included:
- Mini Station beacons connected to high precision depth sensors.
- VTRx on the template, providing link between acoustic communication and umbilical to the vessel.
- High precision acoustic altimeters.
- Topside receiver rack managing display of data, management of system parameters, and forwarding data to customer survey systems.
Multiple sensors allowed redundancy of measurement and quality control, depth sensors provided accuracy to 10 mm while altimeters provided measurement accuracy to 1 mm.
