The complete paper describes the use of a riser for coiled tubing (CT) operations from a monohull vessel already performing riserless well interventions (RLWI). The project was developed by the operator, an intervention-vessel company, and several service providers. The solution covers 200- to 500-m water depths and converts back to riserless operation after CT operations.
Introduction
The operator has more than 600 subsea wells globally in multiple countries and more than 550 subsea wells on the Norwegian Continental Shelf (NCS), which accounts for more than 83% of all subsea wells in the area. Successful interventions here using RLWI vessels encouraged the operator to investigate the possibilities of also performing CT operations from a vessel. The best option was found to be a strategy that included a monohull vessel that could perform both RLWI and CT operations.
The analysis of operations in rough-weather conditions in the NCS showed that riser-based CT operations from such a vessel could be performed in the summer season only.
