Spudcan Leg Penetration Analysis

Fred. Olsen Windcarrier AS Ltd. commissioned Gavin and Doherty Geosolutions to undertake independent spudcan penetration analyses for two sites near Hong Kong in the South China Sea. These sites were the proposed locations of the following wind farms (i) Hong Kong Electric project (close to Lamma Island) and (ii) the CLP project, located slightly further offshore. The purpose of this study was to assess the possibility of employing a jack-up vessel to install suction bucket foundations at these sites.

Scope of Work:

Fred. Olsen Windcarrier A/S Ltd. and Universal Foundations Ltd. were assessing the feasibility of installing Met Mast foundations at two positions in the South China Sea using the Brave Tern jack-up vessel to install the novel Universal Foundation suction bucket foundation. Fred. Olsen Ltd. requested that GDG undertake a penetration analysis to estimate spudcan penetrations at proposed Met Mast locations near Lamma Island and for the CLP Power project.

The penetration analyses were performed in accordance with the recommendations contained in Technical and Research Bulletin 5-5A - Guidelines for Site Specific Assessment of Mobile Jack-Up Units (2008). The extraction analyses were performed using equations derived from centrifuge investigations that modelled the spudcan extraction problem.

The analytical calculations highlighted some installation challenges at these site locations. GDG demonstrated that these challenges could be mitigated through the use of slightly modified installation approaches and by incorporating the use of low pressure jetting for leg removal.