The Mærsk Resilient, the first of four newbuild jackups being built at the Keppel FELS yard in Singapore, is on a three-year contract to work off the coast of Dubai for Dubai Petroleum Establishment. (Image courtesy of Mærsk Contractors) |
In today’s world of constrained assets, the operative word when securing a drilling rig is efficiency. For Mærsk Contractors, efficiency was one of the primary goals when it decided to pursue a construction project that includes four new MSC CJ50-X100 MC jackup rigs.
According to Claus Hemmingsen, chief executive officer of Mærsk Contractors, these rigs will not only be efficient, they will be capable of operating in most parts of the world. The rigs are rated for 350 ft (107 m) water depth in areas such as Asia Pacific, the Middle East and West Africa and for 300 ft (91.5 m) water depth in harsh environments such as the North Sea.
Keppel FELS delivered the Mærsk Resilient, the first rig in this four-rig program in early February 2008. The three additional rigs will be delivered at approximately half-yearly intervals.
Designed in efficiency
Improved efficiency was at the top of the agenda when Mærsk Contractors was designing these new jackups, Hemmingsen said, with many of the improvements obtained by implementing some of the features introduced in the ultra harsh-environment jackup rigs Mærsk Innovator and Mærsk Inspirer (delivered in 2003 and 2004). The company contends these I-rigs have achieved drilling performance improvements of up to 30% over comparably rated jackups.
According to Morten Norderud-Poulsen, project director at Mærsk Contractors, the efficiency design goal for the new jackups is 20% more efficiency than existing rig designs in this segment.
Among the many features copied from the two I-rigs is the XY cantilever, which introduces a range of time-saving improvements. The cantilever design, Norderud-Poulsen said, increases the number of wells that can be drilled from one location. On the new rigs, the cantilever reaches 44 ft (13 m) transverse and 70 ft (21 m) aft of the stern. The combined load capacity of the XY cantilever is 1,280 metric tons at 50-ft (15 m) reach and 685 metric tons at 70-ft reach. “This, along with the increased height of the derrick, allows 29,560 ft (9,015 m) of drill pipe and 13,300 ft (4,056.5 m) of casing to be racked in the derrick at the same time,” he said.
The derrick accommodates stands of drill pipe, bottomhole assembly (BHA), casing, tubing, and liner in lengths up to 135 ft (41 m) compared to 90 ft (27 m) on other cantilever jackups. Skidding between wells and infield rig moves can be carried out with a full setback in the derrick.
The cantilever structure also holds much of the drilling and mud systems. These do not have to be reconnected when moving the cantilever, Norderud-Poulsen explained. Skidding from one well slot to another can be carried out in 30 minutes compared to the usual two hours.
Another capability replicated from the I-rigs is dual workstations on the drillfloor. As the name implies, dual workstations allow for a second string of casing, drillpipe or bottomhole assembly to be assembled or disassembled while the first string is working in the well bore. Fluids handling is also improved, with a dual drilling fluid system for easy change between mud types. These features considerably reduce nonproductive time on the critical drilling path. Furthermore, the drilling equipment on the new MSC CJ50-X100 MC jackups qualifies them for drilling deep and difficult wells, including high pressure/high temperature wells, Norderud-Poulsen said.
Other features
Another innovative feature of the new layout is the positioning of two accommodation blocks around the forward leg and the routing of all ventilation hoods, exhausts, tank vents etc. to the aft jacking houses. This orientation more than doubles the available deck space, Norderud-Poulsen explained, and allows for use of a forklift truck on deck. Furthermore, in the process of implementing this design, variable deck load has been increased to 4,500 metric tons.
Emphasis has also been placed on further improving the safety and the working environment on the new rigs, which have accommodations for 120. The redesign of work areas leaves them free of trip, slip and fall obstacles. As much of the work as possible has been automated, Norderud-Poulsen explained, which further reduces the likelihood of injury. In many instances, he said, “Manual handling is out of the equation.”
Proving the concept
Mærsk Contractors has put forward performance comparisons against other rig designs that indicate the new jackups will deliver 41% improvement on production time for horizontal wells and 25% improvement on deviated wells.
“We expect these rigs will outperform anything in the market,” Hemmingsen said. “With the Mærsk Resilient now in the field, Mærsk Contractors has the chance to prove that these rigs can do what they are designed to do.”
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