While deepwater technology marches forward, combining the latest advances with industry knowledge gathered over the years by experienced operators can result in the most efficient designs.

On Feb. 26, 2014, a subsidiary of Transocean Ltd. awarded contracts to Sembcorp Marine's subsidiary, Jurong Shipyard in Singapore, for construction of two dynamically positioned (DP) ultradeepwater drillships. The two new drillships will be based on Sembcorp Marine’s Jurong Espadon 3T design, incorporating operational input from Transocean on equipment selection and design layout to enhance its ability to deliver drilling and completion efficiencies. The deck and equipment layouts incorporate years of offshore deepwater completions experience including lessons learned from Transocean’s own operations as well as input from oil companies and major oilfield service providers.

The two ships are expected to be delivered from the shipyard in the second quarter of 2017 and the first quarter of 2018, respectively. The combined capital cost for the two drillships is estimated at approximately $1.24 billion, including the shipyard contracts, project management, owner-furnished equipment, inventory and capital spares. The cost excludes capitalized interest.

Transocean also entered into an option agreement to order up to three additional drillships of the same design and specifications on similar terms. The three options must be exercised in half-year intervals, with the first option deadline in the first quarter of 2015.

“These newbuild drillship orders highlight continued execution of our long-term asset strategy,” said Steven Newman, president and CEO of Transocean, in a press release. “We are committed to reinvesting in our fleet through the addition of differentiated, high-specification and high-return assets that will appeal to a wide spectrum of our customers. We are very pleased to partner with Sembcorp Marine’s Jurong Shipyard in this effort.”

Asset strategy

Transocean’s asset strategy is to enhance the makeup of its fleet through the addition of differentiated high-specification, high-return rigs. Over the past five years, Transocean has taken delivery of or ordered 21 newbuild ultradeepwater drilling units and nine newbuild high-specification jackups from various major shipyards.

This continual building process has ensured that the company has remained at the forefront of the shipyard construction process, developing and strengthening relationships with all the major equipment manufacturers and shipyards. Throughout this process the company has developed and implemented robust design verification and quality assurance procedures that ensure its newbuild units are delivered according to plan and operationally ready.

Transocean has a well-established relationship with Sembcorp and currently owns and operates six drilling rigs built by Sembcorp Marine’s yards. This includes three jackups and one semisubmersible rig delivered by PPL Shipyard and two semisubmersibles built by Jurong Shipyard.

Drillship design

Each of the drillships will be equipped with drilling facilities, a larger deck area with an enclosed riser bay in hold, efficient deck arrangement, motion characteristics and a moonpool designed to accommodate a larger riser angle. Although the vessels are expected to be initially outfitted for 3,438-m (8,000-ft) water depth and 10,668-m (35,000-ft) drilling, they are designed to operate in up to 3,658-m (12,000-ft) water depths and for drilling to depths of up to 12,192 m (40,000 ft).

Other features of the Jurong Espadon 3T design include a 1,250-ton-rated derrick and drawworks able to handle up to 20-in. tubular and other pipehandling options, a flexible mud system for completions operations, a DP system that exceeds Class 3 station keeping requirements, and accommodations for a crew of 220 personnel.
The rigs’ favorable motion characteristics come from a bilge keel configuration that provides dampening of vessel roll, resulting in better motion characteristics than other drillships of a similar size.

The equipment and deck layout on the newbuild drillships have been designed with well completion operations in mind. These drillships feature a flexible mud system for completion operations and in-hull riser storage, which increases usable deck space.

Transocean’s patented dual-activity arrangement uses two drilling stations within a single derrick for simultaneous drilling tasks in a parallel rather than sequential manner, improving efficiency in both exploration and development drilling operations.

Each unit will have a heave-compensated crane rated for 165 mt with enough wire to deploy items to the seabed in 3,050 m (10,000 ft) of water.

The units will be fitted with both active-heave drawworks and a crown-mounted compensator on the main load path. This combination allows the benefits of active heave while also providing passive compensation when required for specific operations.

The units will be outfitted with seven-ram, 183/4-in., 15,000-psi BOPs, with the ability to add a second BOP stack.

The mud pits are round and have smooth profiles to allow easy tank cleaning. This makes the pit cleaning operation safer and more efficient.

Transocean’s patented Advanced Generator Protection provides autonomous generator performance in frequency droop mode, thereby minimizing the consequence of any system faults.

The vessels will have Transocean's hybrid power system, Active Power Compensation, which is designed for lower emissions and improved fuel economy. This system will allow a nearly steady load on the power plant regardless of load fluctuations. The hybrid energy storage capability also provides a reserve power that allows some critical equipment to be operated during a loss of main power.

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