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New Generation Of Ultra-Deepwater Rigs Promise To Stretch The Limits




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New Generation Of Ultra-Deepwater Rigs Promise To Stretch The Limits
Depth Quest
By Paul Wells

New Technology Magazine, April 2008 - It might be called the new frontier of petroleum resource exploration. In fact, with most of the so-called "easy oil" already found and the growing global need for energy, the oil and gas industry is increasingly being driven toward the exploration of deep and ultra-deepwater regions, as evidenced by a growing number of projects currently undertaken off Africa, Latin America, South East Asia and in the Gulf of Mexico.


And in using the Gulf of Mexico as an example of the potential of deeper offshore exploration, one can truly appreciate the resources locked far beneath the waters, not to mention the desire of industry to exploit the vast reserves.

According the United States government's Minerals Management Service (MMS), which plays a key role in America's energy supply by managing the mineral resources on 1.76 billion acres of the Outer Continental Shelf (OCS), offshore oil and gas exploration is vital to the country's future energy supply.

It says the approximately 43 million of leased OCS acres currently accounts for about 15% of the U. S.'s domestic natural gas production and about 27% of its domestic oil production.

However, those numbers only scratch the surface of what potentially lies beneath the surface of the ocean floor. The offshore areas of the United States are estimated by MMS to contain significant quantities of resources in yet-to-be-discovered fields, many of them deeper than current offshore activity can reach.

MMS estimates that the oil and gas resources in undiscovered fields on the OCS (2006, mean estimates) total 86 billion barrels (bbls) of oil and 420 trillion cubic feet of gas. To put it in perspective, these volumes represent about 60% of the oil and 40% of the natural gas resources estimated to be contained in remaining undiscovered fields in the U. S.

It's no wonder, then, that a new generation of deepwater drilling rigs have been -- or are in the process of -- being developed in an effort to reach a prize of such magnitude. Among those doing the building are Pride International Inc., MPF Corp., Frigstad Discoverer Invest Ltd. and Transocean.

Pride to christen three ultra-deepwater drillships

Pride International's desire and commitment to enhance its deepwater drilling operations, particularly in the Gulf of Mexico, was verified when it announced in January that it had been awarded a five-year contract from BP for Pride's latest advanced capability ultra-deepwater drillship.

Currently in the early stages of construction at the Samsung Heavy Industries shipyard in South Korea, the unit will be the first of three vessels which combined will see Pride spend more than $2 billion (all figures US dollars) to design and construct.

"The three rigs we are building are largely the same in technical capabilities -- water depth up to 12,000 feet, total drilling depth up to 40,000 feet," explains Pride spokesman Jeff Chastain.

Aside from its depth capabilities, the rig will offer a variable deck load of 20 000 metric tonnes, dynamic positioning in compliance with Class 3 certification, expanded drilling fluids capacity, a 1 000-tonne capacity top drive and living quarters for up to 200 personnel.

The rig is being modified from the original design to improve on its already extensive off-line operational capabilities, Chastain notes, as the unit will boast a 160-metric-tonne, active-heave compensated construction crane that will allow for parallel operations. This will include the placement of production trees and manifolds in up to 10,000 feet of water without obstructing the critical path of drilling deepwater wells, an additional 3,000 feet of marine riser and a corresponding increase in riser tensioning capacity.

"It's more of what we call a total field development type of asset that can drill development wells as well as lay the subsea equipment that has to be in place to begin the flow of oil and gas once there's some type of collection system that's been designed and installed," Chastain says.

"Whatever you are lifting can be laid down on the ocean bottom at the side of the rig as opposed to going through the moonpool, so you are not disrupting the drilling operations that are ongoing."

Including the modifications to the rig's technical features, commissioning and systemnintegrated testing, the company has revised the estimated cost to construct the rig to approximately $730 million.

MPF contracts world's biggest drillship

MPF is building what it claims is the world's largest and most versatile drillship. When all is said and done, the $640-million vessel will be about 950-feet long (290 metres) and have storage capacity for one million bbls of crude oil and 700,000 bbls of segregated ballast in the double-hull tanks.

The hull has two moonpools, one for drilling and the other for production operations. The vessel is Class 3 dynamically positioned and is double ended so that environmental force can be minimized by changing the heading no more than 45 degrees.

"The drilling equipment is rated for water depths to 10,000 feet [expandable to 12,000 feet] and drilling depths to 35,000 feet. There is ample free deck space aft for production equipment and cargo offloading gear," explains Roger Mowell, MPF's senior marine and drilling system adviser.

This combination of drilling and production capabilities will allow the vessel to perform extended well testing, early production or even full field development in some instances, he adds.


"Extended well testing will provide very valuable reservoir data that will reduce risks and improve the economics of deepwater field developments."

Future drilling vessels will be required to work in even deeper waters and drill to deeper depths, Mowell notes, and to attain these goals will likely require reducing the weights of drilling risers, casing strings and drillstrings.

"The most promising prospect for such reductions is the use of different, highercost materials such as titanium, carbon fibre or composites," he says. "Efforts are also underway to increase the capacity of the equipment in the lifting load path such as the travelling block, the top drive and the motion compensator."

Frigstad targets most challenging wells

Frigstad is currently constructing a sixth generation ultra-deepwater semisubmersible drilling rig that it says will be the largest such unit ever built.

Under construction at Yantai Raffles shipyard in China, with contract delivery expected in September 2009, the estimated total project cost for the rig is $600 million. It is the first unit to employ Frigstad's D90 design.

"The design philosophy applied for the D90 was that it should be optimized for operations in all ultra-deepwater areas worldwide, except for the Nordic Seas, and it should be able to handle the most challenging wells that can be expected," explains Harald Frigstad, chief executive officer and founder of the company.

"This enabled the rig to be designed for optimum operations in the areas it will be used, instead of some compromises due to the need for operating under extreme conditions with special regulatory requirements."

As a result, the rig could also be designed to enable fabrication at a lower cost than most other deepwater "harsh-environment" rigs, but still be able to cover nearly 95% of the deepwater locations around the world.

The rig is being prepared for operations in up to 12,000 feet of water and drilling of the most extreme wells of up to 50,000 feet length.


The SS Frigstad Oslo is being equipped with a double drilling derrick of the Ram- Rig design, with 2x1000 short ton lifting capacity. Frigstad says this will be the most powerful RamRig ever built, constituting eight hydraulic cylinders and it will be the 11th RamRig delivered to the market by Aker Kvaerner Maritime Hydraulics of Norway (of which six are double rigs) since this rig system was successfully introduced in 1997.

"For all drilling and completion operations in deep waters the most time-consuming operations are not related to drilling of the wells, but to the operations of running tubulars up and down to the seabed, and in and out of the wells," Frigstad notes.

"One of the main advantages with the RamRig is that it allows a considerable amount of drilling tubulars to be racked vertically in 90 to 100 feet lengths [stands] adjacent to the drilling tower."

He says this eliminates the need for having to pick up and lay down tubulars in nine-to 12-metre lengths from the horizontal racking at the pipe deck and subsequently connected/disconnected at the drill floor, before being run in and out of the well.

As such these operations, which constitutes most of the rig time for offshore operations and in particular in deep waters, can be done much more efficiently.

The D90 allows for vertical racking of 10,000 feet of drilling riser in 100 feet stands (double joints), and 50,000 feet of drill pipes in 90 feet stands (triple joints). As well, most casing strings to be used for the wells can also be made up in stands and stored vertically prior to being run into the well.

In addition, for efficient and economic positioning of the rig, it is being equipped with both eight highly powerful, Class 3 thruster systems and anchor winches that will allow the rig to be hooked up to pre-set deepwater taut-leg mooring systems, for saving of fuel during long-term deployment for field development drilling.

Transocean plans six deepwater drillships

Transocean, which in November 2007 acquired GlobalSantaFe, already has fifth-generation rigs that can operate in up to 10,000 feet water depth and drill to 37,500 feet. Now, the company is building four enhanced Enterprise-class drillships that will further stretch the limits of both water and drilling depth.

Construction of the Clear Leader, a dynamically positioned, double-hull drillship, is underway at the Daewoo Shipbuilding & Marine Engineering Co. (DSME) yard in Okpo, South Korea, with an estimated total capital expenditure of approximately $650 million.

The Discoverer Clear Leader will feature Transocean's patented dual-activity drilling technology, allowing for parallel drilling operations designed to save time and money in deepwater well construction, compared with conventional rigs.

"The dual-activity technology, along with a new and enhanced top drive system, an expanded high-pressure mud-pump system, expanded completions capabilities and other unique features of the drillship target the drilling of wells up to 40,000 feet of total depth," says Guy Cantwell, Transocean's director of corporate communications.

"The rig will have a variable deckload of more than 20 000 metric tonnes and will be capable of drilling in water depths of up to 12,000 feet."

Commissioned by Chevron Corporation and slated to work in the U. S. Gulf of Mexico, the construction schedule calls for the shipyard to deliver the Clear Leader late in the third quarter of 2008 followed by sea trials and mobilization to the Gulf in early 2009.

The three other Transocean drillships to be constructed at the DSME yard are the Discoverer Americas, which will work for Hydro Gulf of Mexico, LLC, Discoverer Inspiration, which has a contract with Chevron, both in the U. S. Gulf of Mexico, and an unnamed unit contracted with BP to work off Angola.

In October 2007, Transocean announced it had entered into a joint venture with Pacific Drilling Limited whereby the combined entity would own two ultra-deepwater Samsung-design drillships that are currently under construction in South Korea.

The new drillships feature National Oilwell Varco drilling packages that include advanced offshore drilling technology, including significant off-line tubular-handling and stand-building capabilities.

As well, advanced mud system designs, advanced systems for building, storing and running several subsea trees and efficient riser and BOP (blowout preventer) handling systems are part of the package.

"Deepwater Pacific 1 will be equipped to work in water depths of up to 12,000 feet and outfitted to construct wells up to 35,000 feet deep," says Cantwell, adding construction cost for the vessel will be about $685 million, excluding capitalized interest.

The construction schedule calls for the shipyard to launch the hull in late March 2008, and then deliver the rig late in the first quarter of 2009.

Deepwater Pacific 2 will be able to perform in water depths of up to 10,000 feet, upgradeable to 12,000 feet, and is designed to construct wells up to 35,000 feet deep. The estimated delivered cost for the Deepwater Pacific 2 is approximately $665 million, excluding capitalized interest.

Construction is expected to be completed in the fourth quarter of 2009.

CONTACTS FOR MORE INFORMATION

Cynthia Bowen, Pride
Tel: [phone]
E-mail: [e-mail]
Roger Mowell, MPF, E-mail: [e-mail]
Harald Frigstad, Frigstad, E-mail: [e-mail]
Guy Cantwell, Transocean, E-mail: [e-mail]