PIPELINE CONSTRUCTION BOOMING IN NORTH SEA

The boom in North Sea pipelining forecast for the early 1990s is under way.

Three major projects-two gas lines and an oil line-have started in the central U.K. North Sea. Next year activity will extend into Norwegian and Dutch waters.

BP Exploration has started work on a replacement for the Forties oil line and a line to bring sour gas from Miller field to St. Fergus, Scotland, also the destination for Mobil North Sea's Beryl gas line.

Activity is also brisk in the Southern basin, although individual projects are not the same scale. BP completed the line serving Amethyst gas field. ARCO British and Shell U.K. Exploration & Production received approval for the Pickerill and Clipper lines.

BIGGEST PROJECT

The biggest single pipeline project planned for the North Sea is the Zeepipe system linking Sleipner gas field in the Norwegian sector to a new terminal at Zeebrugge, Belgium. Statoil, operator for construction and operation of the line, said project engineering is nearly complete. European Marine Contractors will lay the line in the 1991 and 1992 weather windows.

Zeepipe consists of a 500 mile, 40 in. sector from Sleipner to Zeebrugge and a 25 mile, 30 in. line from Sleipner to the Statpipe riser platform on Block 16/11.

Zeepipe is to start up in 1993 to handle first deliveries from Sleipner. Norway's gas business will spawn a number of other pipeline contracts. Norske Shell, operator for development of Troll field, will require twin 37 mile, 36 in. wet gas lines linking the field to onshore processing facilities north of Bergen.

The onshore plant will be connected with the Sleipner-Zeebrugge section of Zeepipe through a 184 mile, 40 in. line. There are also plans for a 114 mile, 36 in. link from Oygarden to the Heimdal end of the Statpipe system. A link from Oygarden to Troll might substitute for the Heimdal sector, depending on future gas sales.

Statoil has studied two alternative routes for another pipeline link between the North Sea fields and either Germany or Netherlands. A decision is expected shortly.

The Sleipner project will also require a 140 mile, 20 in. line to transport as much as 130,000 b/d of condensate from the field to the Karsto gas plant north of Stavanger, starting in 1993.

In the Dutch sector, Elf Petroland and NAM plan a 200 mile gas pipeline providing a north-south spine to established infrastructure, which covers central and western parts of the Dutch offshore.

Elf Petroland said work will begin on the pipeline's first stage in 1991. The line will be completed to a gas/condensate field in F3 in 1992.

FORTIES REPLACEMENT

BP Exploration's decision to replace the 105 mile, 32 in. pipeline between Forties field and the Cruden Bay terminal north of Aberdeen demonstrates the strength of the third party gas transportation business in U.K. waters.

BP decided to lay a 36 in. replacement that would boost capacity of the Forties system to 900,000 b/d from 575,000 b/d after discovering corrosion on the first 12.5 miles of line from the Forties C platform to shore.

If handling declining production from Forties field had been the only consideration, the company could have kept the old line by extending pigging and inspection.

But third party transportation is now big business. It was clear that BP would be gathering revenue from its pipelines long after Forties was depleted. The new pipeline cost 162 million ($292 million) and should be in service later this year.

Opportunities presented by third party business also led BP to revise plans for a liquids line serving Bruce field. It replaced the proposed link from Bruce into Brae with further connection to the Forties system, due to start up in early 1993, with a direct 150 mile, 24 in. link to Forties.

The new line will be able to handle output from a number of prospects in the Bruce area in addition to the 70,000-80,000 b/d peak from Bruce.

THE MILLER PROJECT

BP's second major pipelaying project this season is the 150 mile, 30 in. sour gas line from Miller field to St. Fergus.

The gas line and a 5.6 mile, 18 in. liquids line from Miller to Brae will be completed this summer. The lines will be tied into the platform during 1991. A feature of the offshore section of the line will be installation of two 30 in. subsea isolation valves close to a double-valve tee about 650 ft from the platform.

The Castoro Sei lay barge has laid a dummy spool that will be replaced next summer by the section containing the valves and tee. This area will be covered by a 300 ton tubular frame. Again, third party gas business played a role in design of the line. The double-valve tee will enable gas from another development to enter the system without passing through the Miller platform. There are three other tees along the route.

Onshore, Total Oil Marine has started work on a reception terminal for the 200 MMcfd of sour gas from the field, which will be transported from the platform to shore in the dense phase. The gas has been sold as generating fuel to the Peterhead power station 11 miles away.

BERYL LINE

Mobil started work in June on the 30 in., 210 mile pipeline that will link the Beryl riser platform to new terminal facilities at St. Fergus.

The pipeline and terminal will cost 300 million ($540 million). First gas is due ashore in October 1992. Work this year also includes laying of a 5 mile, 16 in. gas pipeline between the Beryl A and B platforms and installation of a riser tower near Beryl A.

The 5,500 metric ton structure will provide capacity for use in gas injection and gas sales. It also will provide entry points for production from future Beryl projects, including satellite fields.

All gas lines from subsea wells, currently running through the Beryl A utility shaft, will be rerouted through the riser tower.

Beryl gas will provide a peak throughput of 240 MMcfd. But if, as expected, the Marathon-led Brae group exercises an option to take a 50% equity stake in the pipeline and terminal, volumes would rise considerably.

The U.K. Department of Energy has told Mobil and Marathon that it does not want a proliferation of small diameter pipelines in competition with each other and will allow only one major new pipeline in the area.

All gas produced in the central and northern North Sea is transported to the huge reception and treatment terminal at St. Fergus.

But Amoco U.K. Exploration has broken tradition for south-central gas with the Central Area Transmission System (CATS). The system involves a 266 mile, 36 in. line to Teesside in northeastern England. First gas through the system will come from Everest and Lomond gas fields for sale to a cogeneration plant planned for Teesside by ICI and Enron Corp. The fields have reserves of 1.5 tcf and will produce 320 MMcfd of sales gas and 21,000 b/d of liquids by 1994.

The line transporting wet gas to Teesside terminal will cost about 460 million ($828 million), while the cost of the two offshore field developments will be about 725 million ($1.3 billion).

The line has a capacity of 1.4 bcfd, allowing for third party business from the central North Sea.