PACE-SETTING FIELD DEVELOPMENT UNDER WAY OFF EUROPE

Among the latest action:

Norske Shell last week lowered into position on Block 31/6 off Norway its Troll field gas platform, said to be the largest object ever moved on the face of the earth.
The 430 m tall concrete structure was ballasted to lower it into place in 300 m of water in the North Sea. Then the platform's 19 skirt piles were plunged almost 36 m into the seabed to fix it in place for development of the eastern part of the field.
Another platform, the world's first concrete semisubmersible production unit, is to be installed in the west part of Troll field this year. It will produce much of the field's estimated 380 million bbl of oil reserves (OGJ, Jan. 23, p. 66).
Conoco Inc.'s Norwegian unit christened the world's first floating oil production platform built entirely of concrete.
The massive 220,000-ton Heidrun field tension leg platform (TLP) will be installed in late June in the Norwegian Sea in 350 m of water. Heidrun field, 112 km south of the Arctic Circle, is the industry's northernmost offshore oil and gas field development.
Mobil North Sea Ltd. won U.K. Department of Trade & Industry approval to develop Galahad field in the U.K. North Sea using a monotower. Mobil aims for an industry speed record by taking Galahad from definition engineering to production in only I year.

TROLL GAS PLATFORM

Shell's Troll gas platform began its 180 mile journey from Vats fjord north of Stavanger to the installation site May 12 and arrived May 14. Bad weather during the next few days forced Shell to delay the final move.

Ten large tugs, with total pulling power of 130,000 hp, performed the tow at a rate of 1-2 knots. The tugs moved in a star formation to help position the platform..

The platform weighs 1.05 million metric tons. Only 22,500 metric tons will be topsides because most gas processing will be carried out onshore at Kollsnes terminal north of Bergen.

Wet gas will move 65 km to shore through two 26 in. pipelines. After processing at Kollsnes, gas will be sent via the North Sea gas grid to Zeebrugge, Belgium, and Emden, Germany, for distribution to customers in France, Netherlands, Belgium, Germany, Austria, and Spain.

Troll field holds estimated gas reserves of 46 tcf, of which about 30 tcf will be produced using the Troll gas platform in the eastern part of the field. East Troll development is expected to cost $5 billion.

Troll's gas platform is to begin production Apr. 1, 1996, and operate for 70 years. Plateau production is to reach 30 billion cu m/year early next century

A Shell official said "everything went okay" with platform installation. Preparations are under way to begin a drilling program in June. Forty wells - 39 producers and one observation well - will be drilled by the end of 1997.

Shell plans to have 14 wells on production when Troll gas flows ashore Oct. 1.

HEIDRUN TLP

Conoco christened its Heidrun TLP in Gandsfjorden, Stavanger, Norway (OGJ, May 15, Newsletter). Among its innovations is a titanium drilling riser.

Heidrun production will begin in August from predrilled wells. Peak flow will be 200,000 b/d of oil late this year. Heidrun field holds reserves of 750 million bbl of oil and 1.6 tcf of gas.

Oil will move to shore by a direct tanker shuttle loading system, eliminating the need for storage facilities.

Gas production will be reinjected at first but later will serve as feedstock for a methanol plant under construction by Conoco and state owned Statoil at Tjeldbergodden in mid-Norway. A 16 in. pipeline from the field to the shore will be laid in summer 1996.

When production begins, Conoco will turn over operation of the platform to Statoil, which will operate the field from its new operations center at Stjordal, Norway.

GALAHAD FIELD

Mobil began design work on its Block 48/12a Galahad development project last November. Production start-up is due in October.

Mobil said gas will be produced through the North Sea's first multilateral horizontal well. Production from the not normally manned monotower is expected to average 50 Mmcfd from field reserves estimated at 153 bcf.

The platform is under construction at the Nigg yard of Brown & Root Highland Fabricators Ltd. in Scotland. It is designed to stand in 19 m of water and carry a 1,000 metric ton topsides.

The platform is being built to the

Amoco minimum offshore support structure (Amoss) design developed by Amoco (U.K.) Exploration Co. (OGJ, Mar. 27, p. 30).

Highland Fabricators built two platforms to this design for Amoco's Davy and Bessemer field developments, also due on stream in October.

Mobil said Amoco allowed use of its design as a result of "the spirit of cooperation throughout the industry" resulting from U.K. operators' Cost Reduction Initiative for a New Era (Crine) program.

A Mobil official said operators are creating a pool of knowledge from which each can take information.

While Amoco did not receive payment for use of the design, Mobil will pass on information gained from Galahad, so Amoco can streamline developments using Amoss in other southern North Sea fields.

A 16 km pipeline will tie in Galahad platform to the existing Lancelot export line operated by Mobil. Galahad gas will join production from Mobil's Lancelot, Excalibur, and Guinevere fields en route to the Bacton, U.K. terminal.

Phillips Petroleum Co. U.K. Ltd., operator of Bacton terminal, will assume operatorship of Galahad platform. Mobil's share of gas will be sold by Mobil Gas Marketing (U.K.) Ltd.