Cost effective shallow water subsea intervention on lift boat with cantilever deck

• Taqa required support for a subsea well intervention campaign in the Dutch sector of the Southern North Sea to: establish if sustainable production from the well could be reinstated and if not, prepare the well for a future abandonment programme; conduct a variety of interventions ranging from wireline fishing, to water shut off, re-perforating, and well testing
• In line with Taqa’s existing contracting framework, Expro were appointed lead contractor to both modify the vessel ready for subsea well intervention and manage a well services alliance comprising Expro, BJ Services and BakerHughes
• Taqa identified that a self-propelled lift boat could be modified to perform shallow water subsea well intervention, however the vessel selected for this campaign was not equipped with a moon pool, and required a cantilever for this operation

• Key to achieving well re-entry was the fabrication of a cantilever deck that could be skidded over the top of the subsea well to form the work platform for intervention equipment
• A cantilever deck was designed and manufactured by Expro – a primary feature was its ability to index through nine positions to centre itself over the well
• Over a 14 day period, project-specific rig vessel modifications were undertaken to pre-install well service equipment, comprising surface well testing, coil tubing, e-line and slickline packages, this also included the installation of flare booms on the port and starboard sides of the vessel
• Once on location a riser was installed and the well intervention began with well inspections using Expro’s slickline services to establish if the wells were clean of debris from surface to the reservoir – the slickline was used to recover the fish and mechanical plugs previously installed in the well
• Wireline was used extensively throughout the project using Expro’s combined e-line and slickline units to minimise number of coiled tubing operations
• The first well required milling to clear blockages in the tubing and a cement plug to be set on top of a mechanical bridge plug
• The programme also called for production logging and then additional perforating
• In order to clear a restriction in the well, the tail pipe was cut off using an Expro radial cutting torch

• Improvement in productivity following the successful intervention of three wells
• Significant savings – avoided the need for a jack-up rig or intervention vessel
• Single project manager on multi interface project – high operational efficiency
• Fast track delivery using vessel of opportunity with custom modifications

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