Introduction to the Frigg Cessation Project
Authors: Berger Jean-Claude 
Published: May 2011

The Frigg Cessation Project was the largest decommissioning project undertaken in recent years and included the removal of six topsides, three steel jackets and sealines with an estimated weight of 87.000 metric tonnes. The magnitude of the project and the fact that the field straddles the border line between Norway and UK makes it unique. Both British and Norwegian statutes apply on Frigg, depending on the location of the platforms. It had been therefore necessary to find an agreement with relevant authorities of both countries so that the decommissioning of the Frigg field can be handled as a single unit observing both sets of national statutes.

This paper presents a brief description of the Frigg field with its installations to be decommissioned and disposed of, the process and schedule followed by TOTAL to define the decommissioning scope including public consultation of the stakeholders and preparation of the cessation plans for submission to the regulatory bodies. The paper will also present the main phases of the offshore preparation and removal of the installations and the Company organisation set up to manage and follow the execution of the work.

Introduction

The Frigg Field was a natural gas reservoir that extends across the border between the Norwegian and British sectors of the North Sea Continental Shelf (Figure 1).

Thee Frigg Field was first discovered in June 1971 on the Norwegian block 25/1. In April 1972 gas was also encountered in the neighbouring block 10/1 located in UK (United Kingdom). In July 1973 the Frigg Licenssees signed a Unitization Agreement regulating the development and the operation of the field.

The Frigg Field was developed in accordance with the provisions of the agreement between the governments of Norway and the United Kingdom and known as the Frigg Treaty signed in May 1976. Under the provisions of the Frigg Treaty, Elf Norge, now Total E&P Norge, in Stavanger, was defined as the Operator of the Frigg Field while Total Oil Marine, now Total E&P UK, in Aberdeen, was defined as Operator of the gas export system consisting of two 32?? pipelines from Frigg to St Fergus Gas Terminal in Scotland and one intermediate riser/compression platform MCP01 located midway of the export lines.

Development of the Frigg Field took place between 1973 and 1977 and consisted of five platforms (Figure 2).

Three of the plarforms were located in the UK water, one drilling and production platform (CDP1), a treatment platform (TP1) and a living quarter platform (QP). The two others installations were located in the Norwegian sector, one drilling and production platform (DP2) and one treatment and compression platform (TCP2).

Three of the platforms, TP1, QP and TCP2 were permanently linked and formed what was known as the Frigg Central Complex (FCC).

Three of the platforms, CDP1, TP1 and TCP2 as well as the intermediate platform MCP01 had concrete " Gravity Base?? Substructures, the two others QP and DP2 had steel jackets substructures. The topsides of all platforms consisted of steel decks supporting a number of modules and pieces of equipment.

First gas was produced from Frigg to St Fergus in September 1977.

End October 2004 the Frigg reservoir was finally shut in having delivered about 192 billion Sm3 of gas to the UK domestic market.