Motion CompensatedPile Drillingin Limetree Bay
Project Specifications
The Case
Limetree Bay Refinery (now named Ocean Point Terminal), located off the coast of St Croix USVI, required a new CALM buoy to serve as an offshore loading terminal. This buoy would connect to the onshore production refinery and enable the tanker to take on oil in the optimal position relative to prevailing weather conditions.
To install the CALM buoy, seven anchor piles had to be drilled in water depths from 80 to 270 meters. These piles would secure the buoy to the seabed with catenary chain legs.
Conventionally, this process would be conducted on jack-up barges. Yet, with large water depths of up to 270m, a sloped seabed of 17 degrees, and varying seabed conditions (sand in shallow water, limestone in deep water), jack-up barges could not be used.
An alternative floating solution was required. However, strong swell at the project site limited the uptime on traditional drilling vessels. This was costly, as waiting for peak weather conditions would delay the project.
Our Solution
We partnered with Large Diameter Drilling to place the T700 with a reverse drilling rig (the LD2500) atop on the SBM Installer. The use of the T700, with its ability to compensate for wave heights of up to Hs 2.5 meters in periods of 4-18 seconds, provided an 80% workability increase.
The T700, alongside the LD2500, was mobilised in Rotterdam in 2019. The LD2500 was mounted to a cantilever beam which was subsequently affixed to the T700. Once in use at the Limetree Bay Refinery, the combined systems operated for over 24 hours non-stop, in sea states of up to Hs 2.5 meters without performance loss. This solution installed one anchor pile a week, across the entire process of drilling, anchor pile installation, and grouting.
The collaboration between Barge Master and Large Diameter Drilling completed a world first: drilling operations from a diving support and construction vessel (DSCV) in water depths in excess of 270 meters. The installation of the seven pile anchors was successfully executed, and this solution now has proven potential for industry-wide application. Barge Master’s T700 ensured a steady and balanced platform, enabling a secure drilling operation, from a floating vessel, under highly challenging conditions.
