Excalibur jack-up innovations improve efficiency, safety and quality of Codling Wind Park site investigation

Codling Wind Park is a proposed offshore wind farm in the Irish Sea set in an area called Codling Bank, approximately 13 km to 22 km off the County Wicklow coast. It is being developed by CWPL, a 50/50 joint venture between Fred. Olsen Seawind and EDF Renewables.

CWPL required a detailed offshore geotechnical investigation to provide sufficient geological and geotechnical information to:

• Investigate ground conditions at the offshore locations

• Characterise in situ soil mass properties at the locations

• Obtain and establish parameters required for detailed design

The target scope of works was:

• 15 continuous sampling boreholes

• 15 seismic cone penetration tests (CPT)

• P-wave check shot logging at selected locations.

• P-S suspension logging

• Associated laboratory testing

• Associated written reports

Initially, we proposed the jack-up platform Excalibur to undertake the full-scope of works as opposed to using a traditional survey vessel as it was more suited to the water depths at the site. We advised that this would provide better operability and sample quality due to increased stability of the drill string and larger deck space on the jack-up for in situ and offshore lab testing. After assessing the metocean and ground conditions, we identified that unique modifications would be needed to Excalibur to tackle the high current, tidal velocity and range, as well as the soft, variable soil conditions.

To allow the jack-up barge to cope with the challenging conditions, our in-house engineering team designed and fabricated several bespoke pieces of equipment in our marine engineering workshop. These included:

Complex environment riser casing system

The anticipated primary constraint of this site was the strong current and how it would affect the riser casing when placed in the water. To mitigate this, we designed and built a specialised riser casing specific to the metocean conditions. The utilisation of the additional bespoke 20” riser casing to withstand the metocean conditions at the site ensured the efficiency of the operations.

Sliding drill deck to allow multi point locations

The sliding drill floor was designed to meet CWPL’s requirement of achieving the collection of 2 columns of data at each test location. The specification called for a CPT and a sample borehole to be completed at each location. By sliding the drill floor without moving the barge to a new position, we saved the client up to 12 hours of marine operations at each location cutting a potential three weeks off the schedule (including weather).

Casing handling equipment to facilitate rapid deployment

We created a better system for setting up and deploying long, large-diameter casing safely, reducing manual handling and limiting the interaction between workers and equipment. We improved casing lengths and connections to make assembly easier and used the latest wireless bolt torquing technology to ensure strong connections suitable for marine environments, balancing mechanical design and ease of use.

These tailored innovations provided numerous benefits to the project's operation and efficiency, such as:

• Reduced risks to equipment and staff during drilling through the bespoke riser casing and tipping system, minimising manual handling and improving stability against site currents

• Streamlined data collection and saved time on the schedule with the sliding drill deck

• Significant environmental benefits from utilising a jack-up rig, reducing carbon dioxide emissions by approximately 6.7 times less embedded CO2 per test location compared to a dynamic positioning drill vessel