Subsea wireline well intervention has been performed from the Multi functional Support Vessel (MSV) Seawell since 1988. In a joint Coflexip Stena Offshore (CSO) and Cameo venture, an impressive track record in wireline work and abandonment has been created. Despite this, there is a growing need for developing the range of services to provide deep water well intervention and coiled tubing activities. This paper presents Coflexip Stena Offshore's current capability and experience and future strategy. This includes extending the range of the existing system for operations in water depths down to 3,300 ft (1,000m) and modifying it to allow for riser and coiled tubing compatibility.
The CSO Seawell is certified as an offshore installation capable of handling hydrocarbons at surface. Utilising a derrick structure, situated above a dedicated 22fl (7m) x 16 ft (5m) moonpool, well re-entry, wireline, pumping and abandonment tasks can be performed. Such tasks include gas lift logging, perforating, cementing and setting plugs. Observation Remote Operated Vehicles (ROV) are an integral part of every well senicing operation, and the vessel can be equipped with a work-class Multi Role Vehicle (MRV).
The first stage of developing Coflexip Stena Offshore's integrated subsea well intervention services is to extend the range of the existing system from 600 ft through to 3.300 ft Modifications required include a new umbilical, incorporating an MRV operated panel on the lubricator and upgrading the lubricator winch wire and the four guide wires. The existing MRV unit has been successfully utilised in deep water diverless pipelay operations and can be fully equipped for well servicing operations
Following the above modifications a coiled tubing and tie-back riser system will be developed. This new system will allow for a smooth subsea changeover from normal wireline to tie-back riser activities by incorporating a high angle connector on the lubricator, compatible with the tie-back riser and the lubricator stuffing box. Coiled tubing equipment will be efficiently located on the vessel by modifying the existing equipment and vessel handling systems This will include a purpose built injector head lifting frame to allow the injector assembly to be racked back into the derrick when not in use. A hydraulic control system will be required to power the coiled tubing equipment and will be a permanent feature on the vessel. Thus only an injector head and tubing reel would have to be mobilised for standard coiled tubing jobs, reducing time for overall mobilisation.
The development of this integrated service from a dynamically positioned monohull will place Coflexip Stena Offshore in a unique position to take up the challenges of deep water West of Shetland and world wide.