WATCHING THE WORLD PETROJARL, SEILLEAN PERFORMANCE

The floating production test ship Petrojarl 1 continues to prove itself one of the most useful pieces of equipment when it comes to evaluating reservoir performance of North Sea fields before completion of development plans.

Its current job, the extended test of a horizontal well drilled into the oil zone of Troll oil and gas field for Norsk Hydro AS, Oslo, could lead to a reevaluation of Norway's gas development strategy.

The oil zone has flowed at unexpectedly high rates throughout the first 4 months of this year with few interruptions, a remarkable performance during a particularly stormy season.

LITTLE DOWNTIME

During the winter Petrojarl 1 has shown 96.6% availability with 1.6% planned downtime, leaving only 1.8% unscheduled downtime during a period when storms halted tanker loading from Statfjord field, normally little affected by the weather,

The vessel's owner, Golar-Nor Offshore AS, Trondheim, now plans a followup vessel that will extend the successful principles of Petrojarl 1 to a full early production vessel capable of handling a combined 80,000-100,000 b/d from as many as 20 wells. The ship is to be 250 m long with storage capacity of 500,000-600,000 bbl.

Golar-Nor is negotiating with shipyards in Europe and Japan and hopes to place a construction contract by the end of the summer.

Like Petrojarl 1, the new vessel will be custom built to operate in the unfriendly waters of Northwest Europe. The construction contract will not depend on an agreement to use the vessel in a specific field. However, Golar-Nor has identified four or five fields off the U.K. and Norway where it could be used.

The only other ship based production vessel in the North Sea is British Petroleum Co. plc's custom built Seillean, which has just started commercial operations in the U.K. sector.

The 45,000 dwt Seillean hooked up to the two horizontal wells in Cyrus field in Block 16/28 of the Central North Sea and has started individual tests of each well. Production will be increased shortly to about 15,000 b/d.

Seillean will be able to store about 310,000 bbl of Cyrus crude before it must sever wellhead connection and depart for a terminal. BP expects to take 1 month to load the first Cyrus cargo, which will be discharged in Rotterdam.

TESTS, MODIFICATIONS

Since it was completed in the Belfast shipyard of Harland & Wolff last year, Seillean has been undergoing sea trials. It ran a series of tests on a dummy wellhead off the west coast of Scotland.

As a result of those tests, modifications were made which lead to a textbook operation on the first live wells. The vessel's process facilities, particularly the separation units, also performed well during the first spell of typical North Sea spring weather.

BP developed the vessel as a vehicle to tap many small North Sea oil fields that cannot support stand alone production facilities.

Cyrus's 13 million bbl of reserves will keep Seillean employed for the next 3 years. BP has several other followup options, including the 2 million bbl northwest lobe of Forties field and a discovery in Block 15/20a, which holds reserves of 21 million bbl.