NORWAY Vigdis cuts subsea costs 50% compared with Tordis

Adoption of the principles which have now been endorsed by the Norsok campaign is helping Saga Petroleum to find viable development solutions for fields which under the traditional approach proved uneconomic. A clear example is provided by Vigdis. In mid-1992, according to Knut Taranger, vice president for engineering in Saga's technology and development division, this project had costs of Nkr8.2 billion and is estimated to take 45 months to implement. Two years later, the costs have been

Apr 1st, 1995

Adoption of the principles which have now been endorsed by the Norsok campaign is helping Saga Petroleum to find viable development solutions for fields which under the traditional approach proved uneconomic. A clear example is provided by Vigdis.

In mid-1992, according to Knut Taranger, vice president for engineering in Saga's technology and development division, this project had costs of Nkr8.2 billion and is estimated to take 45 months to implement. Two years later, the costs have been reduced to Nkr5.1 billion and the implementation period to 36 months.

The long haul in search of a viable production solution ended last October when the final parts of a plan for development and operation (PDO) were submitted to the Norwegian Petroleum Directorate (NPD). Having been involved in discussing the plan as it was formed, the NPD was able to give its formal approval in a mere six weeks.

In many ways, Vigdis is a copy of the Tordis subsea project which Saga brought onstream last year. The main contractors, for example, are those which worked on the Tordis - ARB Offshore Technology for the subsea production facilities, Stena Offshore, now Coflexip Stena Offshore, for the pipelay and tie-ins, and Nyme for fabrication.

"We took off some of the gold plating used on Tordis, "says Taranger. "We used functional specifications and we picked the long-lead suppliers early to get their information into the project. Now we are selecting the suppliers and fabricators during the conceptual phase to get their feedback."

But Saga has not slavishly followed the principle of standardization. Vigdis will not have the same central manifold as Tordis - instead the 12 subsea wells will be placed on three four-slot templates, two for production wells and one for a water injection well.

"Subsea technology is evolving so fast that it creates problems for standarization," says Taranger. "You can lose money by insisting on standardization when a more cost-effective concept has become available."

The bottom line is that for Vigdis the unit subsea well costs have been cut by 50% compared with Tordis.

The field, which contains reserves of some 2.9 mcm of oil and 2 bcm of gas will be tied back to the Snorre TLP, where virtually all the facilities handling its production will be provided in a 1,600-ton reception module. It is due onstream in mid-1997, but this date could be advanced, Taranger says.

Work is also proceeding on the small Tordis East structure, which holds some five million cu meters of oil. A PDO is due to be finalized towards the end of the year with startup perhaps taking place in 1997. The project calls for two-to-four wells tied back to the Tordis manifold. The manifold has additional slots for such tie-backs, but is also flexible enough to allow existing wells to be disconnected and new wells linked in.

Hence it will be available as a tie-back point for the H Field. This consists of a central and northern part, both of which still require appraisal, but could be brought onstream towards the end of the decade.

The Tordis Fields, Vigdis, and the H Field all lie in Saga's golden block, 34/7. This is also the location of the one billion bbl Snorre Field, which is itself still under development. Saga submitted a PDO for development of some 22 million cu meters of oil reserves in the northern part of the field, but this will be timed to come onstream as production from the main field peaks in about three years.

But perhaps Saga's biggest challenges lie in the fields which are the subject of a deal with Statoil last year. In exchange for ceding the operatorship of Midgard to Statoil, the company acquired interest in the Smoerbukk fields and the operatorship of Fenris.

Copyright 1995 Offshore. All Rights Reserved.

More in Subsea