Ken Richardson and Ian Simpson, of ABS, review current deepwater drillship designs and technologies.
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Friede & Goldman’s DS3810 deepwater drillship design, which is being evaluated by ABS for AIP, is designed to drill in 14,750ft (4500m) water depth. |
Drillship designs have been in constant evolution since the first units appeared more than 50 years ago. While the industry has experienced ups and downs, investment has continued into developing deepwater assets with more and more advanced capabilities.
As a classification society, ABS provides third-party review of new or novel design concepts. Approval in Principle (AIP) is granted in acknowledgement that a proposed concept or design complies with the intent of ABS Rules and/or appropriate codes. Over the past three years, AIP has been awarded to a number of design concepts for ultra-deepwater drillships.
Expanding capabilities for HPHT environments
In 2013, ABS was selected to work with Keppel Offshore & Marine (Keppen O&M) on the Can-Do drillship, a proprietary design for deepwater exploration and development drilling and completions. The design was developed in a joint effort between KOMtech (Keppel O&M’s research and development arm and technology center) and partner GustoMSC. ABS’ scope of work included plan approval for basic and detailed design, including structure and stability assessments.
While most drillships in operation have been designed for exploration drilling, Keppel O&M listened to industry feedback that indicated the need for vessels capable of performing development drilling and completions as well. The innovative concept took the form of the Can-Do drillship, which is scheduled for delivery in 2016. When construction is completed, the Can-Do will be able to handle next-generation 20,000 psi blowout preventers. According to Keppel, the Can-Do’s large functional deck space will accommodate installation of the third-party equipment required for development drilling and completions. The drillship has a double blowout preventer stack integrated into the design and features a riser hold capacity for 12,000ft water (3660m) depth with the flexibility of storing either 75ft (23m) or 90ft (27m) long risers.
The drillship was model tested at the MARIN facility in the Netherlands, and the hull is being built at the IHI yard in Japan. Topsides and commissioning will be carried out at the Keppel FELS yard in Singapore.
Another relatively recent AIP went to Hyundai Heavy Industries (HHI) for its innovative HD12000 heavy duty, wide-beam drillship design. The vessel will be capable of operating in 12,000ft (3660m) water depths and drill to 40,000ft (12,000m) below the mudline. HHI describes the drillship design as “ready for 20 ksi” because it will be able to accept installation of a 20,000 psi deepwater BOP system.
Design features include a high-capacity derrick and derrick pipe setback, a high-capacity marine riser system and large associated buoyancy, a heavier and taller BOP stack, and storage, handling and piping systems that can support deepwater high-pressure operations.
The drillship’s refined hull form, developed from the company’s experience building merchant ships, will enable a transit speed of 11.5 knots. Additional hull features include integrated, high-efficiency thruster pods and a moonpool designed to reduce internal fluid motions and resistance. The new hull form, in combination with carefully chosen locations for the thrusters, will deliver improved transit speeds and station-keeping performance over previous units.
Capitalizing on size and efficiency
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The Rowan Renaissance, completed in January 2014, was the first drillship in a four-vessel series built using ABS’ ISQM process. Image from Rowan Companies. |
Like HHI, Friede & Goldman has been focusing on efficiency, concentrating its efforts on developing a number of designs that are particularly appealing options for a low-oil-price environment. Among these are the DS 3810 and DS 4500 drillships.
The DS 3810 is designed for operation in 12,500ft (3810m) water depth with 40,000ft (12,000m) drilling depth capability. The DS 4500 is designed for 14,750ft (4500m) water depth and 50,000ft (15,240m) drilling. With a 37,000-tonne payload, a 6800sq m deck area and the capacity to accommodate 250 people onboard, both are designed for 90-day autonomy, which means they can work for three months in a remote location without the need for resupply. The functional layouts for drilling, stand-building, and BOP/Xmas tree handling incorporate space for advanced drilling techniques like managed pressure drilling and dual gradient drilling. The large moonpool, which is 141ft (43m) long, facilitates multiple operations.
Efficiencies are extended by the ability to carry out multiple functions simultaneously. A stand of drillpipe and top hole casing can be prepared while the unit is drilling, and rig moves can be accomplished with setback partially loaded. The design allows a BOP stack to be assembled, connected and tested while the rig is drilling using a separate BOP. The BOP stack can also be hung off while a Xmas tree is being deployed or while the vessel is moving to a new location. The drillship can carry two BOPs with the possibility of eight rams in a 15,000-20,000 psi BOP stack and can accommodate various drilling packages.
Another significant factor in this design is the focus on emissions. The units are fitted with integrated ballast water treatment and IMO Tier III low fuel-consumption engines. Enhanced power management capability reduces the drillship’s impact on the environment and improves fuel efficiency.
Efficiency, reliability improved through ISQM
As control systems for offshore assets become increasingly more complex and highly integrated, successful implementation relies heavily on the software developed by multiple vendors and the many interfaces required for software integration. Verifying and validating these software packages and the ways they interact is essential to safe operations.
Integrated software quality management (ISQM) provides guidelines for managing software over the entire life cycle of an offshore asset. ISQM was first used by Rowan Companies in the construction of four high-specification ultra-deepwater drillships, the Rowan Renaissance, Rowan Resolute, Rowan Reliance and Rowan Relentless at the HHI yard in Ulsan, South Korea.
Rowan Companies stepped forward to apply the new systems, processes, and technologies of ISQM on high-end GustoMSC P10,000 design units. The four vessels can drill to 40,000ft (12,000m) in 12,000ft (3660m) water depth. They are DP-3 compliant and have dual-activity drilling capability with a maximum hookload capacity of 1250 tons featuring three 100-ton knuckle boom cranes and one active-heave 165-ton crane for deploying subsea equipment. They are designed with a 4 million pound riser tensioning system, two seven-ram BOPs, incorporating full acoustic backup control, and five mud pumps with dual mud systems. The units have a variable deck load capacity of 20,000-ton and can accommodate 210 people.
Using the ISQM process gave the drilling contractor and yard a software development and maintenance tool that allows software verification to take place at the time of installation and provides a way to monitor for consistency and reliability when software updates or hardware changes are made over the asset’s service life.
Because ISQM is a methodology, it requires no new equipment. The focus is on software and interface quality, with the goal of reducing the number of errors related to software and integration. In its first application on the Rowan Renaissance, completed in January 2014, ISQM facilitated the reliable integration of products from more than half a dozen major suppliers and more than 35 subsystems on a single drillship.
In its application on these four high-spec vessels, ISQM is helping to maintain system integrity and reduce the risk of safety, health and environmental incidents. It also makes it easier to manage operational and project risks, decrease NPT, review for compliance to specifications, manage programming challenges, simplify programming validation. ISQM makes it possible to identify and address challenges in a way that minimizes schedule and cost escalation.
LNG-fueled drillships
Another way ABS is involved in progressing innovation is through joint development projects (JDP). A recent example is the JDP with Daewoo Shipbuilding & Marine Engineering (DSME) that has the goal of delivering the world’s first drillship fueled by natural gas. The plan is for fuel to be stored onboard as LNG.
The project will address challenges associated with safe storage and handling of LNG, bringing DSME’s experience in LNG vessels together with ABS’ technical standards and experience as a pioneer in the classification of drillship and advanced LNG technologies.
DSME’s part of the JDP includes concept design, comparison between two types of LNG containment technologies and analysis of the vessel’s fuel gas supply system, while ABS’ role includes concept design review, basic engineering review and a risk assessment of tank spaces, access areas, fuel gas supply system and machinery spaces.
The project team sees the Gulf of Mexico as a key market for this unit because inexpensive US gas would allow operators to reduce running costs while also lowering emissions to meet the strict sulfur requirements in the North American emissions control area.
Innovating for tomorrow
Drillship designs will continue to evolve to meet the changing demands of the offshore industry. As innovation propels the offshore energy sector into new areas, services like AIP will continue to have value, helping to make sure safety and reliability keep pace as technologies emerge and mature.
Ken Richardson is executive vice president of Global Offshore Energy Development for ABS in Houston. He has been active in the marine and offshore industries for more than 30 years. Richardson leads the international technology business development team from the ABS Energy Corridor office in Houston.
Ian Simpson is director of Offshore Technology and Business Development for the ABS Offshore Sector Team based in Houston. A 40-year industry veteran, he coordinates survey, engineering and R&D and commercial efforts at ABS. Simpson’s experience encompasses marine and drilling operations, technical and regulatory support, new construction projects and existing unit maintenance and repair.
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