Cookie cutter approach pays drilling dividends

ENSCO 8505, the sixth in a series of seven ultra-deepwater semisubmersibles, recently arrived in Texas for final trials before launching a two-year stint under contract to Anadarko, Apache and Noble Energy in the Gulf of Mexico. Russell McCulley was on hand in Corpus Christi, where Ensco executives gathered to talk about the rig, the benefits of standardization and the company's aggressive plans for its drillship and jackup fleet. 

If the ENSCO 8505 holds no new surprises for those who've been following the 8500 series since the first rig entered service in 2009, it suits SVP and CFO Jay Swent just fine. The rig came out of the same Keppel Fels yard in Singapore as its sibling semis, and boasts the same specs: 8500ft operational water depths, 35,000ft maximum drilling depth, 240ft x 255ft main deck, and so on. Take a crew member off the 8500, put him to work on the 8506, to be delivered later this year, and he may not notice much difference.

‘When we talked to people back in Singapore many years ago about the 8500 series strategy, we made the point that we were taking a common design, building it cookie-cutter style, one after another in the same shipyard, and that that was going to lead to tremendous financial benefits,' Swent says.

'That was a theory then. Today, it is reality, and we have become absolute devotees to standardization.'

Ensco was not the first driller to recognize the benefits of standardization but it arguably has been most successful carrying out the strategy, with its semi fleet as well as its Samsung (SHI) dynamically positioned drillships. ‘We have also benefitted from standardization across our premium jackup fleet for rigs that have similar equipment, particularly those rigs that were built by Keppel Fels,' Swent notes.

Jay SwentConsistency of design, drilling equipment and shipyard construction, he says, has helped avoid cost overruns and construction delays, and curried favor with clients: the 8500 series experienced 97% utilization in 2011, and only six of the company's 40 premium jackups are cold stacked.

Ensco early last month announced the order of the ENSCO DS-8, the sixth in a series of Samsung DP3 ultradeepwater drillships, scheduled for delivery in 3Q 2014. To be built by SHI in its Geoje, South Korea shipyard, at a cost of about $645 million, the DS-8 will sport a number of enhancements over its DS series predecessors, which are based on Samsung's 96K design, socalled for its 96,000t displacement. The new vessel will be capable of drilling in 12,000ft water depths with a total depth drilling capacity of 40,000ft. Other enhancements include retractable thrusters, belowmaindeck riser storage, triple fluid systems and improved crew quarters. Based on the Samsung GF 12000 hull design, the DS-8 will measure 755ft in length and 125ft in width, with a payload that exceeds 22,000t and a 1250t hoisting system.

Ensco has options for two additional drillships of the same design.

John KnowltonThe new rig will be the first ultradeepwater drillship to use the GF 12000 design, says John Knowlton, Ensco senior VP technical.

While better suited to mild environments – which is where the majority of the world's deepwater prospects lie, Knowlton points out – premium drillships are in demand because they offer up to three times the deck space of semis and accommodations for both the materials and crew needed for complex deepwater operations.

According to Knowlton, there are currently 45 Samsung 96K rigs on order.

Samsung ‘has done extensive model testing on this design over the last two years', Knowlton says of the GF 12000 hull. ‘We believe this newgeneration drillship offers significant advantages, with numerous improvements over the 96K design, and therefore we have chosen this design for our future ultradeepwater newbuild program.'

The GF 12000 – the name an amalgam of ‘Green Future' and the vessel's 12,000ft water depth capability – sports a 13ft narrower beam than the 96K and, at 77,000t, a much lower displacement. The ENSCO DS-8will have a mud volume of 16,700 barrels, and if the 1250t hoisting capacity seems like overkill at the moment, it won't for long, Knowlton says.

Above: The ENSCO DS-8 drillship will be the first ultra-deepwater. Left: Ensco is developing an ultra-harsh environment rig

Deepest drilling

The Gulf of Mexico‘s Lower Tertiary represents ‘the deepest drilling ever done', he says. Casing loads necessary to carry out ultradeepwater operations are approaching 2 million pounds. ‘In the future, we're going to exceed 2 million pounds,' he says. ‘2.5 million pounds is certainly where we need to be going on these future rigs.'

The new design will be able to set back up to 48,000ft of 16in casing and rack back 40-45,000ft of standard drill pipe and 10,000ft of landing string, he says. By moving riser storage to the hull, deck space is freed up and the vessel will have better roll motion. The ENSCO DS-8 also represents the company's first use of active heave compensated drawworks.

Ensco will take delivery of the first of three ENSCO 120 series ultra-premium harsh environment jackups in 4Q 2013.The vessel's retractable thrusters will allow scheduled and unscheduled maintenance out of water during operations, dramatically reducing downtime, explains Knowlton, who calculates that retracting the forward thrusters will reduce fuel consumption by as much as half during transit.

At six rams and expandable to seven, the rig's BOP stacks comply with current regulations as well as what Ensco believes future, more stringent regulations could entail.

On the jackup front, Ensco last year ordered three ENSCO 120 series ultra-premium harsh environment units for the North Sea market. The first of the rigs, contracted to Nexen for 4Q 2013, is expected to arrive in 2Q 2013, with the ENSCO 121 and 122 available for service in 4Q 2013 and 3Q 2014, respectively. ‘Although the main area of focus for the 120 series was the North Sea, these rigs are worldwide rigs,' says Roper, Ensco's senior director of capital projects.

Ensco used the occasion to announce its entry into the ultra-harsh environment jackup market, with a new series of rigs under development. ‘We are currently calling it the ENSCO 130 series, and its targets compete with the very largest jackups with a much reduced cost structure,' Roper says. The new rigs will measure 160ft between the fore and aft legs and have 185ft of transverse space between the aft legs, compared to 156ft between the aft legs of the 120 series. The equipment layout will be similar to the 120 series, he says, but with a bigger deck and 150 single person cabins. The base configuration will allow for operations in the UK, Dutch and Danish sectors of the North Sea up to 60° north, which includes block 9.

Richard RoperThe 600ft legs will enable the rigs to work in 430ft water depths in harsh environments and a possible 560ft of milder water depths.

‘We would have to add a bit of leg to do that, but that is very deep water for a jackup,' Roper says. OE


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