Although most observers accept that when it comes to arctic-dedicated drilling rigs it might be another 10 years before various competing vessel designs currently on the drawing board evolve into actual live units, some of those studies are already well advanced.

Ulstein Sea of Solutions (USOS) is one vessel designer at the forefront of the industry’s drive to find answers to the multitude of problems posed by the icy frontier that faces those looking to explore and produce from its depths.

The company’s AXDS drillship design has had Statoil as a driving force behind it as that operator continues to push industry suppliers and itself via its “Arctic Step-up” program to evaluate and expand the industry’s offshore toolbox as part of the Norwegian player’s own strategic move into more northern waters in the Barents Sea and beyond. USOS has worked with partners such as Aker Solutions and NOV earlier this year on different versions of the AXDS design for Statoil to consider.

The operational profile and resulting requirements are out of the range of existing drillships, and simply winterizing equipment and vessels is not enough to meet the design requirements of the Arctic, said Bob Rietveldt, USOS’s original founder and managing director. But designing and building an Arctic-dedicated drill-ship from scratch using proven components is certainly not beyond this industry’s ability. “It’s science fiction, but it’s not Star Trek,” Rietveldt said. It could be perhaps five to 10 years from becoming reality, he added, though admitting that five years was perhaps “ambitious.”

The potential price is certainly not out of this world: The unofficial build cost is estimated at up to US $1.2 billion for such a vessel. Expensive, yes, but is it too much? Bearing in mind the potentially devastating financial penalties that any drilling-related environmental incident would undoubtedly incur on a company – as well as the potentially disastrous impact it could have on the ultra-sensitive Arctic ecosystem and environment itself – and the cost of ensuring that the company has equipment that is fit for purpose, thereby minimizing the possibility of any such incident occurring, it begins to look like a good investment.

The Ulstein AXDS design is a dedicated, self-propelled dynamically positioned arctic drillship developed via a feasibility study in close cooperation with the company’s selected technology partners. It features the Ulstein X-BOW, an inverted bow design that essentially turns the notion of how a bow should look on its head. Launched in 2005, the backward-sloping hull design is now in use on around 50 ships and offshore vessels, including anchor-handlers, pipelay, and construction units. Its benefits include improved handling in rough seas, less drag, and therefore more speed and better fuel efficiency.

The hull design itself was inspired by vessels dating back to the pre-Viking days of Norway – with ships found dating as far back as 700 AD with rounded bows – so it can be safely stated that it is indeed a well-proven design.

Within arctic regions the vessel is described by USOS as being able to self-support for 140 days and would be capable of sailing through 1.2 m (4 ft) of sheet ice stern-first.

The drillship itself is not an ultra-deepwater unit, USOS marketing and sales manager Nick Wessels said. It would, however, be capable of drilling in up to 1,300 m (4,265 ft) in harsh open-water conditions such as in the Barents Sea and in water depths of between 100 m and 500 m (328 ft and 1,640 ft) in managed ice conditions (in areas such as the Beaufort Sea).

For depths of up to 500 m the vessel would be moored, while in the deeper waters it would operate on a Class 3 dynamic positioning system. In both cases it would use a disconnectable turret, enabling emergency disconnect procedures. In such a case it is estimated that the vessel would be able to reconnect to a well in about eight hours.

Some of the most visible concessions to the environment in which it would operate in can be seen in the accommodation areas, which would feature an atrium allowing any available daylight to reach all the single cabins. The drilling work area itself also is fully covered by a composite shelter, with a heating, ventilation, and air conditioning control system also in place using a heat-recovery system.

There also are two helidecks, which would be positioned forward and aft on the AXDS for increased availability, as well as two hovercrafts with sheltered embarkation areas onto ice. One of the helidecks would be a low-level structure for safer operations in foggy weather (a whiteout).

The drillship, which would have an overall length of 232 m (761 ft), would be assisted throughout its ice-managed operations by ice breakers.

Wessels said the AXDS would have a “workable season” of 120 days during the summer in the Beaufort Sea, drilling probably just a single well each season. It would then be expected to travel between the Barents and Beaufort seas during the late summer or early autumn, drilling in open water in the Barents during late autumn, winter, and spring.

“Although it is designed as an arctic drillship, the vessel will be able to operate for nine months of the year in very rough open-water conditions,” he said.

The drillship would in many other aspects be similar to its existing XDS 3600 design, with dual-derrick configuration (almost a prerequisite these days for all newbuild rigs), 20,000-psi subsea well control equipment, and the capability to handle and store a second BOP.

Arctic operational considerations

  • Large ice forces;
  • Extreme temperatures;
  • Sea ice/sea spray icing;
  • Long periods of darkness;
  • Sensitive environment;
  • Limited experience for drilling operations;
  • Emergency and safety preparedness;
  • Long supply lines;
  • Zero discharge requirement;
  • Managed ice;
  • Strong focus on HSE;
  • Strong focus on accessibility and maintainability of equipment; and
  • Small environmental footprint.