Next-generation semi replaces derrick with multipurpose tower
Huisman also designing circular semi with enclosed drilling system targeting Arctic operations
By Joanne Liou, associate editor
With the implementation of the multipurpose tower (MPT) on Noble Drilling’s Noble Bully I and II in March and April 2012, followed by the Noble Globetrotter I in July of that same year, Huisman saw the culmination of more than a decade of work on a technology the company believed could replace the traditional derrick on new-generation drillships. Now, the company, led by CEO Joop Roodenburg, is continuing that entrepreneurial spirit to next-generation semisubmersibles not only with the Orion-class semi, which also features the MPT, but also with the circular Arctic S semi design. The Arctic rig design, which has been under development for more than four years, uses its circular shape to deflect and break ice and has a completely enclosed drilling system, Mr Roodenburg said in an interview with Drilling Contractor.
The Orion semi design aims for a more compact size compared with other rigs providing the same drilling/water depth capacities, which would reduce fuel use and emissions. Both mid-water depths (maximum 1,500-meter waters and 10,000-meter wells) and ultra-deepwater depths (maximum 3,000-meter waters and 12,000-meter wells) are possible. Huisman completed the first concept design in early 2011 and received DNV approval that same year. By the end of 2012, the first basic design was completed, and a second basic design of a larger version was completed in June 2013. Design work is still ongoing as Huisman works on improvements based on feedback from class societies and field experience from the four operational Huisman drillships. In April, the company submitted the basic design to DNV and ABS and expects to receive approval by the end of October.
Mr Roodenburg noted that the MPT eliminates the V-door limitation of traditional derricks, allowing large objects to be skidded or hoisted with cranes directly to the well center or in the moonpool area. “We also have a complete flush floor, which improves all the handling because everything is on the deck,” Mr Roodenburg said. The entire hoist system for both sides of the MPT, including hoist winches (drawworks) and the passive heave compensator cylinders, are placed in the enclosed MPT. While the typical drillfloor is approximately 15 meters above the main deck, the Orion’s design puts the drillfloor at the main deck level. “That means no stairs or platforms and no handrails.”
The flat main deck space and a drill floor flush with the main deck leads to a lower center of gravity, he explained. This increases vessel stability, which results in a high payload/displacement ratio. For example, the Huisman drillship design features approximately 20,000-ton payload with approximately 54,000-ton displacement, while traditional drillships have approximately 20,000-ton payload with approximately 100,000-ton displacement, according to Huisman.
For the Arctic S semi, Huisman completed ice and wave testing in Finland in May 2013. The rig’s structural design features a conical column and a round deckbox that is heavily strengthened at the waterline to deflect and break ice. While a conventional square or rectangular semi has two pontoons with four to eight columns on which the deckbox rests, the combination of a round pontoon with a conical column makes the Arctic S unidirectional and allows ice deflection regardless of its heading.
“When you are in ice, you have horizontal forces, which is why we chose a round design,” Mr Roodenburg stated. This means that the rig will be able to stay on location no matter which side ice comes from, he added. Since ice loads are too big for a DP rig, a 16-point mooring system would let the rig operate in ice-infested waters between 115-ft to 3,000-ft deep (35 meters to 1,000 meters).
The design also includes a derrick-type structure with dual drawworks. Further, the entire drilling system – derrick, working areas, ROV areas and riser storage – would be enclosed to enhance the working environment for the crews in Arctic conditions. The unit is designed to operate in three modes: as a conventional semi resulting in very low motions in waves; a strengthened ice-resistant semi when operating in deep draft in ice; and a gravity-based structure in shallow water so that the unit can be ballasted and rest on the seabed.
From concept to reality
Industry’s frequent reluctance, Mr Roodenburg said, to accept different and/or innovative technology continues to be a significant challenge for companies like Huisman. “That’s a problem in the industry. They only believe it when they see it,” he commented. For example, Huisman was designing the MPT as far back as the mid-1990s, an idea that came about as the company was designing semisubmersibles for Pride Brazil. In 1999, Helix Energy Group Solutions ordered the first MPT for the Q4000 multipurpose intervention vessel. “The tower was delivered in 2000, and we thought, ‘Now it will be easy to sell it to the drilling contractors,’ ” he recalled. “But it was not easy at all.”
While the saying goes, “It takes two to tango,” Huisman realized that for capital-intensive drilling equipment, two might not be enough. “In this case, it takes three to tango because you need the drilling contractor and oil company to work together and agree on it,” Mr Roodenburg explained. It took eight more years after the Q4000 for Huisman to secure an order for the MPT for a drilling unit; this came from Shell and Frontier Drilling, which was later acquired by Noble Drilling, in 2008 for Bully I. Three more orders followed, for the Bully II and Globetrotter I and II.
Since March 2012, the three MPT drillships have been operating for Shell in the Gulf of Mexico (GOM) and Brazil. “They are all drilling right now and performing extremely well,” Dieter Wijning, product manager drilling for Huisman, stated. A fourth vessel outfitted with the MPT, the Noble Globetrotter II, will begin drilling in West Africa for Shell later this year.
Designing around mission equipment
In designing the MPT, Huisman removed the steel structure of the traditional derrick and left only the functional components – the top drive, heave compensator, drawworks and connections. “Changing a derrick to a tower is not really changing the nature of the drilling industry; it’s only changing what it looks like, but it has the same functionality,” Mr Roodenburg said. The design places the equipment, such as hoist systems, in the fully enclosed tower, freeing up deck space and reducing risks for dropped objects. The MPT drillships also feature a reduced size, having a displacement of 54,000 tons, while the average drillship has a displacement between 90,000 and 100,000 tons.
With the first MPT drilling rig order by Shell and Frontier, the vessel design was already near completion, and Huisman had to work around a design that was conceptualized with a traditional derrick in mind. “We put our tower on, but a lot of the things on the ship were already there,” Mr Roodenburg said of the two Bullys.
When the opportunity came around for the Noble Globetrotter I, Huisman was able to first focus on the mission equipment – the drilling package – and then design the drillship around that equipment, he said. “You get a much more integrated design” that ensures balance with the hull and creates a better interface, he said. The Noble Globetrotter I began its 10-year contract in mid-July 2012 in the GOM.
For all three MPT rigs in operation, however, Shell and Noble have reported positive feedback and improved performance, with overall downtime averaging less than 2%, according to Mr Wijning. On the Bullys and Globetrotter, casing strings can be built offline and are run at higher speeds, he said. “Especially with top-hole drilling, when you do not have a riser or BOP in place, they can increase the speed of the drilling operation by about 20% to 40%.”
The MPT is also capable of running longer sections of risers since the tower eliminates the V-door. With a traditional derrick, the V-door limits the maximum length of a single riser joint to a maximum 90 ft, but with the MPT, double joints of up to 150-ft (2 x 75 ft) risers can be run, “which means you have only half the connections and you can speed up the running of riser tremendously,” Mr Wijning said.
Huisman, which is already familiar with handling large lengths of pipe from its pipelaying business, finds that handling principles and challenges for both risers and subsea pipelines, are the same. Running flexible pipes with the MPT is still in the early phase, but the company says it sees it as a serious option.
Efficiency gains are also made with the MPT drillships due to their smaller overall size. This means they consume less fuel and require less energy to perform the same tasks. When sailing, the drillships use approximately 50 tons to 60 tons of fuel per day at 11 knots. “A typical drillship sails at less than 10 knots and has double the consumption,” Mr Wijning said. From West Africa to Brazil, the MPT drillships burn approximately 500 tons while a more traditional drillship burns approximately 1,200 tons, he added. “It’s also 3,000 tons of additional carbon dioxide.”
As Huisman works on further innovating rig designs for the industry, the company is placing heavy focus on enabling more drilling automation. “We are currently planning to have fully automated tripping. The driller says, ‘I want to trip in through the hole for 10,000 ft,’ and the system would do the work completely by itself,” Mr Wijning said. Huisman believes that to achieve this type of automation and even go beyond it, drilling equipment may need to take on entirely different looks. Perhaps the standard top drive and roughneck, as well as other traditional equipment, will not be part of the future.
In addition to changing rig designs, Huisman is changing the construction process. The hulls of the Noble Globetrotter I and II were built by STX Offshore & Shipbuilding and Dalian Shipbuilding Industry Offshore Co in China before the hull was shipped to The Netherlands, where Huisman installed the drilling package. “We basically had the complete tower with the driller’s cabin, etc, sitting on our quayside fully assembled and ready for testing. The complete tower was constructed and commissioned to a fully functioning system while the vessel was being built elsewhere,” Mr Wijning said.
Once the Noble Globetrotter I arrived, testing for the tower was complete, and the full drilling package was hoisted onto the vessel in late November 2012. “We signed the final delivery papers in the beginning of March. From installation to final delivery was about three months. In shipyards, you’re busy with the commissioning of certain systems for 10 months to 12 months. That was a huge improvement.”
Using this construction strategy, the company can build equipment at its own facilities, which allows equipment to be tested prior to installation, saving installation and testing time. While the equipment is being built, the vessel can also undergo construction simultaneously, further supporting a shorter build schedule. “We will definitely use that strategy for newbuilds,” Mr Wijning stated. “I do think this is the way forward.”