As the number of subsea wells in deepwater environments increases, companies who operate in these regions continue to seek safer and more viable economic solutions for improving value realization through well intervention. Traditionally, subsea well interventions are conducted from heavy-weight, mobile offshore drilling units (MODUs) with riser packages. Unfortunately, these intervention operationsinvolve significant operating day rates with consequent NPV negative results.

This paper discusses a riserless intervention that was performed from a dynamically positioned multi-support vessel (MSV) that involved setting and recovery of a mechanical flow-control device in a well with a water depth of approximately 1900 m in the South Atlantic Ocean. The technologies and methods used in this intervention proved that these difficult subsea operations can be performed in a much more flexible and financially viable fashion than previously possible with conventional methods. The techniques developed for this operation also mitigated safety concerns for personnel and equipment, while executing the potential high-risk riserless intervention with success.

The paper will cover the record-breaking, light-weight intervention and the technologies used on this campaign that eliminated the need for a traditional MODU. Of particular interest is the unique vessel interface that allowed the operation to be performed safely and efficiently with slickline.

This successful intervention opens new opportunities for safer and more economical interventions in the deep and ultra deepwater arenas.

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