NPD Issues Opinion on Older Installations on Norwegian Shelf

As an increasing number of fields on the Norwegian shelf enter a mature phase, the Norwegian Petroleum Directorate is concerned with ensuring optimal utilization of installations, pipelines and cables, also in the final phases.

This is an important consideration, not least because a large portion of the resource potential indicated in the long-term development path assumes that smaller discoveries are made commercial through being tied in to existing facilities.

The players on the Norwegian shelf are therefore challenged to find creative solutions for tie-in of smaller adjacent fields to existing infrastructure. One example of this concept is Heimdal, originally a production platform for gas now modified to function as a gas treatment center.

This was among the main points addressed by Deputy Director Finn Carlsen from the Norwegian Petroleum Directorate in the talk he gave at the North Sea Decommissioning Conference in the municipality of Os on February 24.

The conference, held for the third time, addresses challenges linked to decommissioning and removal of installations, with special focus on the North Sea. The event runs over two days and attracts about a hundred participants, mainly from the industry.

Demands for removal

In his presentation, Carlsen emphasized that one of the main challenges facing the Norwegian shelf in the next few years is to ensure that the decisions made during the course of a field's lifetime facilitate maintaining a high level of safety as well as safeguard resource management in the final phase of a field's lifetime.

An acceptable safety level must also form the basis for the disposal activities. The NPD's experience is that a good safety level during decommissioning and removal depends on good planning throughout all phases.

The regulations stipulate that even in the early planning stages, consideration must be given to the fact that the installation must be able to withstand the strain of removal. Consequences in relation to remaining lifetime and removal must also be considered in the operations phase and in connection with major modifications.

Under the Oslo-Paris Convention, all installations must be removed after the field is shut down. Exceptions can be made for concrete structures as well as the lower portions of large steel structures.

On the Norwegian shelf, for example, the Ekofisk tank has been exempted from the removal requirement.

A study program under the direction of the Norwegian Ministry of Petroleum and Energy concludes that the recommended disposal solution for pipelines and cables is to abandon them, as long as they have been cleaned in accordance with applicable requirements and as long as they do not impede other users of the sea.

To date, the installations on eight shut down fields on the Norwegian shelf have been removed: Odin, Nordøst-Frigg, Lille-Frigg, Øst-Frigg, Frøy, Tommeliten Gamma, Yme and Mime. In addition, the deck facilities on 2/4-S have been removed from the Ekofisk area. A decision has also been made to remove the installations linked to Ekofisk 1, with the exception of the Ekofisk tank.