A liftboat with well intervention capability should be much more cost-effective than a jack-up and associated assets that are required to operate with it, Gulf Marine Services and workover specialist Dwellop believe
Abu Dhabi-based GMS has secured approval from classification society ABS for an innovative concept it has developed with Dwellop for vessel-based well intervention services.
The innovative cantilever system it has introduced has been installed on the self-elevating support vessel (a four-legged liftboat) GMS Evolution.
Said to be an industry first, GMS Evolution is fitted with a removable skidding cantilever system, installed with a well workover unit designed in partnership with Dwellop AS. The novel removable cantilever system provides an efficient and versatile vessel for well services, according to GMS.
The innovative combination of a self-propelled jack-up with a removable cantilever and workover unit is not only the first self-elevating unit to secure ABS certification but also the first mobile offshore drilling unit of its kind in the industry.
In addition to the workover unit, which can be skidded over a platform or subsea well, GMS Evolution has a speed of more than 8 knots, DP2 dynamic positioning system, accommodation for 150 personnel and cranes including one of 200-tonnes capacity.
The company says installing the cantilever unit on the self-elevating vessel gives it the well intervention capability of a rig and the marine efficiency of a vessel. The new unit is capable of undertaking ESP replacement, workover, well recompletion, change of use, slot recovery, slide recovery and plug and abandonment. The system can provide fast, accurate cantilever action 15 m and up to 8 m in the transverse direction , skidding at 1 m per minute. This means that the drill floor can be centred over the furthest slot within 30 minutes.
The high level of automation built in to the cantilever starts with the pipe-handling crane, which smoothly picks up drillpipe or tubulars from the well deck. A spacious drill operator’s cabin provides an unobstructed view of the drill floor and pipe deck. An automated catwalk machine smoothly conveys pipe and feeds it safely and accurately to the travelling assembly.
The automated topdrive system can hoist and arrange pipe, and an automated pipe handler safely positions pipe for connection. The robust roughneck has a torque capacity of 100,000 foot-pounds (ft lb) and is remotely operated from a safe location. The same level of automation and hands-free operation drives the casing tongues and air-operated slips, removing the need for any personnel on the drill floor. The derrick has a rack and pinion drive system to ensure high levels of reliability and delivers 250 tonnes pulling force and 140 tonnes pushing force. The topdrive engages pipe, delivering 32,000 ft lb at 200 rpm, with full mud circulation. Secondary well control is provided by a 5,000 psi blowout prevention system that transits with the cantilever and 3.5 inch, 5,000 psi choke and kill manifold. The mud system, which is neatly housed beneath the cantilever, has a capacity of 1,500 barrels.
“Our new cantilever system will give clients a range of options in the way they use our barges to service their offshore assets. This system offers cost-effective solutions for work that has traditionally been performed by more expensive non-propelled drilling rigs,” said GMS chief executive Duncan Anderson.
Mr Anderson said it has “opened up a new area of the market that had previously been predominantly served by drilling rigs” at a greater cost to operators. The new cantilever system will be able to replace them.