Riserless Light Well Intervention Vessel

QinetiQ has developed a concept design for a new offshore vessel that will significantly lower cost of workover operations and improve HSE performance.

Main features:-

Riserless Light Well Intervention Vessel
  • Triple-hulled, small waterplane area concept with DP3 class dymamic positioning
  • Year round operability, close to semi-submersible and drillship performance
  • Double the transit speed of typical semi-submersibles and equal to traditional drillships / OSVs and MSVs
  • Five no-splash-zone moonpools
  • Very significantly larger working deck area than DSV/MSV monohulls
  • Lower operating cost, higher HSE performance by design

Exploration and production operators are eager to drive down the cost of the growing number of subsea well interventions in the world’s offshore basins. Keeping subsea completions online is a key concern of production and asset managers, but current approaches to working over these wells can easily reach $5 million per operation. To date no one has been able to deploy a high performance, cost effective vessel that can help to dramatically lower the overall cost of these operations.

Riserless Light Well Intervention Vessel

The trimaran design, a radical departure from offshore support vessel arrangements, is expected to deliver many economic and operating benefits. QinetiQ has designed in significant advantages in the chosen hullform over conventional monohulls:- excellent seakeeping, good transit speeds, ability to arrange five no splash zone moonpools and more deck area. OTG, responsible for the integration of light well intervention systems into the concept, found that the immense deck area available, (some 40% under cover), coupled with the five moonpools, meant that a comprehensive LWI deckspread could be arranged optimally whilst addressing HSE considerations, for e.g. using skidding systems to avoid free lifting at sea etc.

The current seagoing and operating specifications in this joint design meet or exceed all personnel, work and environmental HSE standards. With the Tri/SWATH design, QinetiQ and OTG have designed in greater HSE performance by minimising common offshore vessel hazards and implementing marine best practices.

Concept design achievements:-

Riserless Light Well Intervention Vessel
  • Operations possible in 6.7-m H1/3, 10-sec zero-crossing period waves
  • Derrick pull force of 300 tonnes with two auxiliary moonpool drawworks of 100 tonnes each
  • Design transit speed of 15 knots and radius of action of 1000 nautical miles
  • DP3 dynamic positioning
  • Fuel capacity for 30-day operation, continuous year-long operations
  • Crew of 110 with NORSOK accommodation standards

The Tri/SWATH vessel concept is capable of being adapted to roles other than RLWI operations, for example, concept designs have already been completed for operators interested in riser enabled well intervention and light drilling operations. Operations that require high operability to maximise cost efficiency, whilst needing large deck area and high transit speeds are likely to benefit from Tri/SWATH technology.

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