Deepwater, marginal projects offshore focus

David Knott
Senior Editor

• Development Underway and Expected off Denmark [59090 bytes]

Industry's focus on drilling technology in offshore northern theaters is centered on deepwater and marginal projects.

Updates on new ideas and technological developments in these two areas commanded center stage at the Offshore Northern Seas '96 conference in Stavanger last week.

Highlighting the conference was BP Norge's plans to drill Norway's greatest water depth well.

Meantime, service and supply companies unveiled a host of new designs intended to tackle technical and fiscal hurdles in operating in one of the world's most unforgiving environments.

Deepwater well

BP Norge AS plans to spud a wildcat on its Nyk High license PL218 in the Voering basin off Central Norway in March 1997.

The company claims the license was one of the most sought-after in Norway's recent 15th licensing round.

Water depth in the Nyk High area is more than 1,300 m.

In May BP acquired 900 sq. km of 3D seismic data. The company has chartered Ocean Alliance semisubmersible rig to drill the well, which will be drilled to 5,000 m total measured depth.

BP said, "The target is Cretaceous sandstone in a tilted fault block that has a flat spot. If we succeed in finding oil, production could start as early as 2000. A fast-track program would maximize commercial value and will help to replace diminishing production from BP Norge's Ula and Gyda fields."

New rig designs

Among new deepwater technologies on display, Mercur Subsea Products AS, Harstad, Norway, detailed a prototype rig for heavy intervention and slimhole drilling in deep water, developed under contract to Norsk Hydro AS and Norske Shell AS.

Svein Gleditsch, market director at Mercur, said the rig's main advantage is the heave compensation unit that enables the drill floor to be kept still in relation to the seabed.

"This will enable us to provide the same drilling conditions on a floater as on a fixed platform," said Gleditsch, "and it will be the only rig that will allow snubbing from a floating vessel."

Mercur claims the new rig will help users to reduce drilling costs by 35-40% in shallow water and 40-55% in deep water, through use of slim hole drilling and lighter dynamically positioned vessels.

Gleditsch said the rig is designed to drill in water as deep as 2,000 m. A prototype unit has been built at Harstad, and Mercur has begun marketing the rig to operators.

Maritime Hydraulics AS, Kristiansand, Norway, showed its RamRig concept, in which hydraulic cylinder rams power the top drive. Three RamRig units are already on order, noted Kjell Fredriksen, Maritime's senior vice-president, sales and marketing.

Fredriksen said the first RamRig will be delivered to Reading & Bates Ltd., Aberdeen, for installation on Iolair semisubmersible early in 1997. BP will use Iolair for well workovers in Foinaven field, currently under development in U.K.'s West of Shetland area.

The rig is currently being assembled at Kristiansand and will begin tests next month.

A second RamRig is to be installed by Saga Petroleum AS on Bideford Dolphin semisubmersible. Fredriksen said the rig will be delivered in about 10 months.

Saga has chartered the Dolphin for drilling, workover, and completion work in Snorre and Tardis fields and Vigdis development project.

A third rig has been ordered by Norsk Hydro AS for installation on a wellhead platform to be used in development of Oseberg East discovery. The rig will be used to drill as many as 24 development wells from the platform.

Coiled tubing first

Saga also has plans to drill the North Sea's first multilateral well using coiled tubing, from Snorre tension leg platform (TLP) with a conventional drilling rig.

Knut Pedersen, Saga's project leader for coiled tubing drilling, said the company plans to test the well equipment at Rogalaud downhole test center near Stavanger before taking it offshore.

"We're not going to make the same mistakes as other companies," said Pedersen. "They were too eager to try it out offshore without sufficient onshore trials."

The onshore test is under way and scheduled for completion Sept. 16. Depending on the success of the trial, Saga will make a recommendation on drilling plans in November, with a view to drilling from the TLP in late 1996 or early 1997. The first well will be used for water injection. A producer is envisaged using this technology.

New platform concept

Hollandsche Staalbouw Maat-schappij BV (HSM), Gouda, Netherlands, revealed details of its Self Installable Reusable (SIR) platform concept.

This was developed as a low-cost platform for shallow water marginal fields.

The SIR platform would consist of a topsides as heavy as 1,000 metric tons mounted on a circular gravity base structure (GBS). The GBS in turn consists of an outer caisson-on which the topsides is mounted with three jack-up legs-and an inner caisson holding a frame for well conductors.

Koos Krispijn, HSM marketing manager, explained that the SIR platform is designed to be commissioned inshore and towed out to the field, for installation with pre-installed anchors over the well site. The platform has the capacity to handle six wells.

Krispijn said ballasting of the outer caisson by flooding with seawater, followed by fixing the legs, lowering the inner caisson, and anchoring, typically would take 24 hr.

A SIR platform would cost $9-12 million installed, without processing equipment. The platform is desiged for North Sea weather conditions, for operation in 20-45 m of water.

Krispijn said HSM is in talks with Nederlandse Aardolie Maatschappij BV (NAM) and Elf Petroland BV for deployment of SIRs in Dutch waters. The company has also received queries from the Far East and the U.K., he said.

Diverless wellhead cluster

Subsea Offshore Ltd., Aberdeen, showed a diverless maintained subsea wellhead cluster design, intended for deepwater production.

The company said it is the first pull-in and connection system for flexible flowlines and umbilicals based on use of remotely operated vehicles (ROVs).

Subsea Offshore said the cluster can be deployed from either a drilling rig or support vessel with conventional ROV handling systems. No surface intervention is required after deployment of the tool basket, and tie-ins are completed without interrupting drilling or production operations.

Hitec, Stavanger, showed a modular multipurpose drilling rig for sidetrack and slimhole drilling, workovers, perforation and stimulation of horizontal wells, and full-triple drilling.

Hitec said the rig permits step-by-step investment, meeting current requirements while allowing for simple rig extensions to meet future needs.

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