ANALYSIS AND DESIGN OF ANTI-RECOIL SYSTEM FOR EMERGENCY DISCONNECT OF A DEEPWATER RISER: CASE STUDY

Emergency disconnect of the drilling riser is required when a dynamically positioned deepwater floater has either a driftoff or a driveoff. This cannot be anticipated; therefore, the riser tension setting cannot be adjusted to a preferred value. Hence, following emergency disconnect, highly tensioned risers have been known to accelerate into the diverter housing and lift the rotary table several feet. This paper describes an analysis method for quantifying this problem and how the method was applied to design an anti-recoil system for Sonat's Discoverer 534 Drillship. The ship was being upgraded to operate in 6000 feet of water. The analysis method described was compared to results of a full scale disconnect test in 3700 ft of water. The comparison of analysis to test results was very good. See also the following abstract.