Feasibility Analysis and Application for Cantilever Beam Extension of Self-elevating Drilling Unit

摘要

The operation capacity of some self-elevating drilling units can’t satisfy the development requirement of production wells in Bohai Bay, China. COSL conducted cantilever extension feasibility analysis to upgrade the capacity of some types of jack-up. The requirement of the cantilever beam extension was to be increased from 40ft to 60ft, and the minimum drill load was 150mt at the maximum outreach & transverse shift (60ft outreach and 12ft shift to port). The research introduced several extension methods, and two of which were adopted. The 1st one was to install removable extension parts on the bow of cantilever, and the original beam would be strengthened together with hull, stern, hold down, jacking and holding system. The 2nd method was to install a set of supporting units between cantilever beam stern and the production rig, and the supporting force could be adjustable automatically. By investigating the structural strength with environmental data, it is concluded that the extended cantilever has sufficient strength, and the drilling unit has sufficient elevated stability, preload capacity and holding system to satisfy the requirement of Rules for the Classification and Construction of MODU. By now, the removable extension parts have been installed on rig of HYSY9*, and 3 wells have been drilled at the maximum outreach of the cantilever.