Tordis Background

The field was discovered in 1987 and developed by former Saga Petroleum and started production in 1994. Statoil took over the role as operator 1 January 2003. The Tordis oil field is located in the Tampen area in the North Sea; and the water depth is roughly 200 m. The field was developed as single subsea satellites, tied back to Gullfaks C platform via a central subsea manifold.

Technology Assessment and Qualification Programme

A comprehensive technology assessment has been performed. Key technical elements were classified and given criticality rating. To ensure robustness of critical components and close the remaining technical gaps, an extensive technology qualification programme (TQP) has been performed.(Fig. 1 is available in full paper)

Project Summary

The project is the world's first commercial application of subsea separation (full scale) in combination with water re-injection and multiphase boosting. Subsea process facilities are designed to handle high sand production and contribute to reach 55 percent recovery from a subsea oil field. Injection of produced water will reduce water discharge to sea. A comprehensive technology qualification programme has been performed. Low pressure production is scheduled to start in October 2006, and the subsea processing facility is scheduled to start in October 2007. (Fig. 2 is available in full paper)

Field Layout

The Tordis Subsea Separation, Boosting and Injection (SSBI) station field development will consist of three main structures:

  • Pipeline inline module (PLIM)

  • SSBI station

  • Satellite Xmas tree (water injection)

The purpose of the Tordis SSBI is to separate water and hydrocarbons from the existing Tordis production fluid and to boost production to Gullfaks C by subsea multiphase pumping. The separated water will be injected into a nearby disposal well that is assisted by a dedicated subsea water injection pump, which also will be located at the SSBI.

The two existing flexible production flowlines from the Tordis central manifold (TCM) to Gullfaks C will be disconnected from the TCM and moved and connected to a new PLIM. Flexible production jumpers will be installed between the TCM and the PLIM.

Flexible jumpers will also be installed between the PLIM and the SSBI, and between the SSBI and the Xmas tree. The production from the existing Tordis field will be routed to the SSBI for separation and injection of the bulk water. The resulting production is routed back to Gullfaks C.

The subsea control system will include a dedicated SCM at the SSBI. New control umbilical and HV power umbilical (for the pumps) will be installed from Gullfaks C and terminated on the SSBI. In addition the new control system will boost the existing system.

SSBI Station Process Layout

The production from the existing TCM will be routed to the PLIM and further onto the SSBI and from the SSBI to the receiving facility Gullfaks C. The PLIM also gives a possibility for bypassing of the SSBI.

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