The gas of EAST FRIGG field is produced from two subsea Production Stations and collected by a Central Manifold Station from which it is transported to Frigg facilities for treatment. This paper describes the innovative design of the subsea equipment for coping with diverless installation and long production time.

Two wells have been drilled on each production station. The production master valves are enclosed in the Xmas tree modules while the other valves and sensors are enclosed in the adjacent Well Jumper Module. The whole subsea control system is enclosed in one module on each production station.

The Central Manifold Station includes the isolating valves necessary for the installation and the maintenance of the field. Provision is made for killing any well from this station. A pig trap module can also be connected for cleaning/dewatering the pipe line to FRIGG.

Installation and maintenance of the field are planned to be performed as diverless operations using dedicated tools.


The ELF's East Frigg field development described in the paper "THE EAST FRIGG DEVELOPMENT" can be summarized as follows:

  • Two structures 4 km apart are located 18 km east of the large Frigg field, in the Norwegian sector of the North Sea, on block 26/2 where the water depth is 110 m.

  • The overall production is expected to vary between 1.25 MSm3 /day and 3.25 MSm3 /day and extend over a period of 5000 days.

The field development scheme comprises two production stations with two wells each, located on top of each reservoir, and one central manifold station which collects the gas from the two production stations before transportation to Frigg installations for treatment.

This paper describes the equipment of the stations, the design, the quality requirement and the installation procedures.


The two major technical objectives have been dictated by economic considerations:

  • to exclusively use underwater production systems

  • to remotely control the production from FRIGG installations where resources and treatment facilities are available.

  • The other technical objectives have been dictated by the strategy of ELF AQUITAINE NORGE

  • to perform diverless installation and maintenance of the field

  • to use the SKULD modular concept.


In order to optimize the overall production availability of the field, a field simulation has been set up from the earliest phase of the project.

The field simulation takes into consideration:

  • the development scheme

  • the design of the equipment

  • the reliability data

  • the maintenance policy

  • the specification of intervention support

vessels as well as their mobilization time the duration of each type of intervention. The model calculates the level of production availability that can be expected from the field. By running sensitivity analysis on the various criteria, the development scheme has been finalized, the design of equipment has been optimized and the following main options have been selected.

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