The North East Frigg Field Installations Decommissioning
Authors: Passard J.P. 
Published: December 2007

Foreword : In this paper, field decommissioning means all actions Operator undertakes to decommission installation, to clean, to remove, to dispose and to leave in situ obtaining, an end product which satisfy the Field's Cessation plan approved by Authorities.

The Cessation Plan is the plan that the Operator prepares and submits to Authorities for their evaluation of the solutions to decommission a Field prior the cessation of production.

The North East Frigg (NEF) was put in production in December 1983 and was the first multiwell Subsea Production System (SPS) developed in the North Sea. The six wells drilled through a subsea template and the control station, an unmanned articulated tower, have been remotely controlled from the Frigg Field situated 18 kilometers away. In May 1993, the field was shut in, after having produced 11,6 BSCM of gas. At cessation of field production the decommissioning of the field was executed in 3 main phases:

Decommissioning of the production facilities including production wells, sealines and topsides.

Preparation of the Cessation Plan (leave in situ, removal/disposal of NEF installations). Plan to assist the Authorities' decision process (refer to SPE Papers 27 148 and 37857).

Leave in situ, removal and disposal of the field installations. Phase 1 was completed Summer 94, phase 2 was completed in May 1995 with the approval of the abandonment plan by Norwegian Parliament and phase 3 is about to be completed: The removal and the disposal of the Field Control Station (FCS) from the North East Frigg Field was successfully performed in 1996 and the final well abandonment works were completed in May 1997. The template removal and disposal is planned for the latter part of 1997.

This paper presents briefly the technical, commercial and operational aspects of this project and the results.

Although the NEF field consists of very specific installations, this first case on the Norwegian continental shelf attracted considerable interest in term of decision process, contractual and safety- environmental aspects. This was the first case for the Norwegian Authorities to handle and it can be used as an example for the decision process when removal of other platforms is being prepared in the future. It attracted particular interest in terms of Environmental Impact Assessment, Operation Safety, Waste Management Program, Third Party Inventory etc. However, this does not preclude the need to study each installation case by case.

Introduction

The North East Frigg (NEF) gas field was a satellite of the Frigg Field (see Fig 1), operated by ELF Petroleum Norge as. The field was shut in May 1993 after having produced more than 11 BSCM of gas and was thereafter the first field to be decommissioned in the Norwegian Sector of the North Sea.

This paper, which is a follow up of the SPE 37 857 paper presented at the conference in Aberdeen April 1997, describes briefly the decommissioning, the abandonment, the removal and the final disposal of the NEF installations.

INSTALLATIONS

Figure 1 shows a perspective view of the installations in place on the field for which removal or abandonment have been assessed. They are:

A subsea Template with 6 wells

An unmanned Field Control Station (FCS) comprising of a concrete base, a steel articulated column and a head which houses the helideck, living quarters area and control equipment. Six umbilicals (hydraulic control lines, injection and service lines) connecting the FCS to the template for direct control of the Xmas trees.

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