Riserless Light Well Intervention (RLWI) operations have been routinely performed for more than 25 years in the North Sea, with 5 vessels delivering riserless production enhancement operations in several hundred wells, helping the Operators to increase the oil recovery rates from their subsea fields.

The ability to carry out frequent, scheduled interventions as opposed to remedial interventions has proven to be crucial to realize higher recovery rates from subsea wells. Such operations are becoming more common and are moving to deeper water, which brings increased technical challenges. At the same time, the ability to substitute expensive deepwater rigs with smaller Light Well Intervention vessels can have a major impact on project cost and scheduling and represent an even bigger opportunity for cost optimization.

In 2015 a brand new RLWI vessel and intervention package have become available for operations in deep and ultra-deep water, taking the RLWI capabilities and successful experience of the North Sea to the deepwater subsea fields of Gulf of Mexico, Brazil and West Africa. 10 years of experience and track record have been capitalized into the design of a new and enhanced deepwater intervention stack (Stack 4), which is deployed and operated from a state of the art RLWI vessel, the Island Performer.

The new intervention stack, now at its 3rd generation, brings increased efficiency and reliability thanks to smaller umbilical, optimized deployment sequences, easier maintainability, elimination of use of guidelines and simplified control system.

On the vessel side, the Island Performer benefits from larger size, increased lifting capabilities, higher accommodation capacity, higher work floor positioning allowing less green water on deck, sea current monitoring capabilities through the water column, faster tool change-out thanks to additional deployment capabilities.

The paper will give a detailed account of the opportunities to improve recovery rates in subsea wells by enabling access with this lighter, more efficient, and ultimately more productive intervention method. It will also describe and elaborate on the significant enhancements brought to the design and capabilities of the vessel and of the intervention stack, and will illustrate how these improvements make RLWI even more attractive, efficient and cost-effective for Riserless intervention operations in deepwater wells. The paper will also cover the significant testing and qualification activities carried out during preparation for actual operations, including results from wet system integration testing and actual operations performed to date.

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