簡介：50年前，Transocean 已經(jīng)采用了先進(jìn)的海洋鉆機(jī)，而當(dāng)Discoverer Clear Leader 號(hào)以及其他四艘企業(yè)級(jí)鉆井船出現(xiàn)的時(shí)候，Transocean 又打開了一片超深水鉆探新的天空。該鉆井船具有模塊化動(dòng)臂鉆機(jī)（MDDM），保證鉆井船更安全高效率，維修起來也更便捷。該船會(huì)打破以前三艘的墨西哥灣最深井記錄，努力實(shí)現(xiàn)其12000英尺水深的記錄，總鉆井深度會(huì)達(dá)到40,000 英尺。該鉆井船由韓國造船公司建造。
For more man 50 years Transocean has introduced advanced offshore drilling rigs, and the advent of the Discoverer Clear Leader and four other newbuild enhanced Enterprise-class drillships brings yet another new horizon to ultra-deepwater drilling.
In March, the Discoverer Clear Leader became the first drillship to exit the Daewoo Shipbuilding and Marine Engineering shipyard (DSME) in Okpo, South Korea, where the other four enhanced Enterprise-class drillships (Discoverer Americas, Discoverer Inspiration, Discoverer Luanda, and Discoverer India) are in various stages of construction.
Whether it’s the capability of achieving a world water-depth drilling record or constructing the long-reach deep wells anticipated in the future, these five drillships demonstrate the most powerful and robust technologies designed to date.
World-class performance targeted
To appreciate the enhanced Enterprise-class rigs’ capabilities, consider the Discoverer Deep Seas, one of three existing Enterprise-class drillships that are predecessors to the Discoverer Clear Leader. The Deep Seas holds the current world water-depth drilling record at 10,011 ft (3,053 m) of water set while working for Chevron in the US Gulf of Mexico. On the other hand, the Discoverer Clear Leader, which has a five-year initial contract with Chevron, will be capable of working in up to 12,000 ft (3,660 m) of water and drill wells 40,000 ft (12,200 m) deep, compared with the current industry design limitation of 35,000 ft (10,675 m).
Previous world water-depth records were also set by two other Enterprise-class drillships ? Discoverer Enterprise and Discoverer Spirit. And before them, the Discoverer Seven Seas and other rigs set world records, making continuous improvement a company hallmark that the enhanced Enterprise-class units will seek to emulate.
The Discoverer Clear Leader features several enhancements, starting with a proprietary dual-activity, high-capacity derrick. This derrick has a 2.5-million-pound hookload capacity and a 1,250-ton Modular Derrick Drilling Machine (MDDM) at each of the two drilling centers, compared to the 2.0-million-pound capacity and 750-ton top drive systems on the Enterprise-class units. The Discoverer Luanda will have a 1,000-ton MDDM as it is not expected to drill the long, deep wells anticipated in the US Gulf of Mexico.
Also new for the enhanced Enterprise-class rigs is a hoisting system with an active heave-compensated drawworks in place of the crown-mounted compensator on the Enterprise-class units. Drillers on the Discoverer Clear Leader will use the active heave compensation mode to more finely tune the weight-on-bit to achieve better recovery of cores and improved drilling operations.
The MDDM, jointly developed by Transocean and Aker Kværner MH, is designed to operate 10 years between overhauls and is constructed based on a modular design to enable safer and faster maintenance and repairs in the field when needed.
Increasing safety, saving time
Other enhancements in the drilling area include better ergonomics and friendlier interfacing between people and the machines used to handle pipe, further reducing the amount of manual interface with equipment. Some drilling operations will be conducted with fewer rig crew on the drill floor, as drillers and assistant drillers more efficiently handle dual-activity operations with Cyberbase technology by National Oilwell Varco (NOV).
Inside the drillers’ cabin, four “cyber chairs” ? two for drillers and two for assistant drillers ? look out over the drill floor and up into the derrick. Joysticks and touch-screen controls help reduce fatigue as each team of driller and assistant driller works together, simultaneously operating the dual-drilling centers.
Taken together, these and many other enhancements increase safety and decrease the time required to complete many operations.
A similar approach to improved performance takes place on the port side of the moonpool, where the vessels feature a dedicated subsea tree preparation area. Protected from waves and wind, three full-size, fully assembled trees can be prepared and tested before running them to the sea floor. Using the blowout preventer handling system saves tree-handling time associated with 80- to 100-ton trees that no longer have to be handled in multiple pieces due to weight handling limitations and the space available on existing rigs.
Below deck the units will have enhanced drilling and completion fluid capacity and pumping capability. Five 7,500-psi NOV Hex mud pumps, a novel concept designed to enhance performance, versatility, and efficiency in a smaller design pump, are installed on the Discoverer Clear Leader and Discoverer Inspiration. The Discoverer Americas will have four Hex mud pumps. The liquid mud system includes provision for more than 20,000 bbl of liquid storage with multiple pumps and manifolds, giving the capability to segregate water-based muds, synthetic oil-based muds, and completion fluids. A key benefit is that days of operations can be saved when switching from circulating mud to circulating completion fluid and back again.
Extra shale shaker capacity is also built into the new rigs with 10 Brandt LCM-3D shale shakers, two more than on the existing Enterprise-class units. If one of the shakers encounters a problem, it can be bypassed using the additional shaker capacity without having to shut down the entire mud processing system.
Like their predecessors, the five newest rigs will feature well-testing capabilities in which well-test fluids are designed to flow directly into the hull of the ship instead of a barge tendered by the rig. Each ship’s fluids capacity exceeds 100,000 bbl, with the ability to test wells flowing at up to 20,000 b/d.
This capability saves the time and cost of scheduling barges. In addition, the drillships can have the well-test equipment replaced quickly if fluid-handling requirements change, an enhancement from the Enterprise-class vessels.
Step-change improvement
Another improvement in operational reliability and flexibility is the “Sixth-Generation Power and Propulsion System” of the new drillships. It marks a step-change in overall power system predictability and radically raises the reliability and availability of power generation, propulsion, and drilling systems. In short, the system helps prevent electrical faults and then manages the power plant so as to tolerate faults when one might occur, avoiding the possibility of power interruptions on the rig. With the added power system reliability, crews can operate with fewer engines on line and operate the engines at more optimum loads, leading to lower fuel consumption, lower emissions, and less wear and tear on the machinery.
Other environmental features include a triple-barrier fluid-containment system that drains and contains separate fluids, a “green” hydraulic fluid biodegradable to more than 95% in seawater, a mechanical skimmer to pick up debris in the moonpool, and fluid-transfer hoses that shut off entirely if they inadvertently loosen during an operation.
These and other enhancements are complemented by a comprehensive waste-management program, the company’s Environmental Management System, and Green Team members who champion environmental stewardship on Transocean’s rigs.
Environmental performance means more than having state-of-the-art waste compactors; it also means operating more in harmony with nature. For example, the Discoverer Clear Leader and its sister units have an optimized hull, similar to that of the Enterprise-class drillships but improved to enhance motion characteristics, deck-load capacity, and mobilization speed, all within a double-hull design.
All of these improvements reflect the tremendous efforts of personnel from Transocean, Chevron, DSME, and dozens of vendors, whose combined expertise totals hundreds of years of the most extensive knowledge in the offshore drilling business.
But the best is yet to come.
As the Discoverer Clear Leader sails toward its assignment as the first enhanced Enterprise-class drillship, everyone involved is looking to achieve the best possible safety, performance, and efficiency. If the past is any indication of the future for this rig and its sister units, world-class performance is just over the horizon.
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