This paper discusses the prejob research and eventual use of a hydraulic workover (HWO)/snubbing unit for a subseaflowline intervention at the Nansen Spar in the Gulf of Mexico (GOM). Located in a water depth of 3,670 ft (1119 m), theNansen Spar has been in production since 2002 (Fig. 1). In 2005, a number of umbilical lines became plugged, preventingfurther chemical injection to prohibit hydrate and paraffin buildup. In 2009, a hydrate blockage formed in a productionflowline during the course of an unplanned shut in. Initially, it was decided to perform a coiled tubing (CT) intervention toenter the flexible riser and flowline, clean out the paraffin, and remove the hydrate deposit. During the CT intervention, thepipe became stuck, thereby requiring a fishing operation. At that time, the decision was made to use a 340K hydraulicHWO/snubbing unit to fish the CT and clean out the remaining paraffin and hydrate bridges. The execution and outcome ofthe fishing and cleanout operation are discussed, as well as some of the challenges associated with not only working in deepwater, but through a flexible riser as well. Recommendations based on the lessons learned during the planning and executionof the operation are also presented.
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