The Veslefrikk concept represents a new way to layout an offshore production and drilling facility. A drilling wellhead platform (VFA) is connected to a floating production vessel (VFB), which is a converted drilling rig.
This paper presents the general philosophy for developing the concept, split of systems between the platforms, and highlights specific features of the system design.
Major modifications to the existing rig systems, and handling of the documentations for these systems will be described.
The Veslefrikk field is an offshore oil field located as shown in Fig. 1.
During the spring of 1986 the oil prices fell drastically, and this reduced the need for drilling rigs in the North Sea. that time a Norwegian rig owner was constructing a forth generation drilling rig on a four-year charter to Statoil at a South Korean yard. The drilling rig was to be delivered to the rig owner by the end of 1986. Because of the reduced need for drilling rigs as a consequence of the reduced oil prices, Statoil proposed considering the use of the drilling rig as a production vessel at Veslefrikk. A brief study carried out by the rig owner revealed that the rig could be used as a field installation on Veslefrikk in combination with a sub-sea installation. Other concepts than sub-sea installations with transfer of the well stream in flexible hoses to the production vessel were studied in order to reduce or avoid the use of flexible hoses. The final solution was to use a drilling wellhead platform connected to VFB by flexible hoses, and a telescopic bridge. The concept is shown in Fig. 2.
Stabilized oil is transported in a 16 " pipeline to the Oseberg A platform and from there in a 28" pipeline to a crudeoi1 terminal at Sture on the Norwegian West Coast. The gas delivered from Veslefrikk is to fulfill the following specifications:
Cricondenbar pressure: < 110 barge
Cricondentherm: < 40°
Water content: < 40 mg/sm3
Carbon dioxide content: < 2.0 vol.%
Dihydrogen sulphide content: < 2.5 ppm
Pipeline inlet pressure: 167 barg
During the initial study phase of the project, in the summer of 1986, it became evident that the converted floater could accommodate all process, utility and mud handling required.
The philosophy for VFB was to keep modifications to a minimum, and to use as many as possible of the existing systems for the production vessel.
