Ekofisk II - Planning for Low Operating Costs Through Lifetime
Authors: Skrede R.O. 
Published: October 2008

Abstract
The age of the existing Ekofisk platforms, together with the fact that they are sinking due to subsidence caused by compaction of the reservoir formation, has made the Ekofisk II redevelopment to extend the economic life of the gigantic North Sea Ekofisk field necessary. The redevelopment of the existing Ekofisk Center comprising ten platforms with two new platforms, 2/4X and 2/45, brought about the challenge to drastically reduce the operating costs to support the extension of the economic life well into the next century. The new Ekofisk II facilities including pipelines have a design life to year 2028, extending the field life from the original production license end date of year 2011. The design accommodates 20 meters of total subsidence. The new platforms are based on the best available proven technology. The design is based on life cycle cost effectiveness. Equipment supplier involvement and functional specifications have been implemented. Operations and maintenance expertise have been an integral part of the project team to ensure that the design is geared toward cost effective maintenance. Planning for low operating costs through lifetime have included measures from the very start of the project through all phases of the project. At the heart of these measures has been a systematic approach to through lifetime cost considerations as well as extensive involvement of operations personnel from day one. The new fit for purpose facilities with reduced staffing requirements have provided the basis for achieving a cost effective operation of Ekofisk.

Introduction
The Ekofisk Area fields (Production License 018) comprise eight fields in the southern part of the Norwegian Sector of the North Sea, Figure 1. The Ekofisk Field development has since the discovery in 1969 followed by a pilot production start in 1971, progressed through several phases the last being the implementation of full field waterflood. Figure 2 shows the historic and forecasted Ekofisk Field BOE production profile. The first Ekofisk Field permanent development installations which became operational in 1974, consisted of three drilling and production platforms (2/4A, 2/4B and 2/4C), a field terminal platform (2/4FTP), a concrete gravity base crude oil storage tank (2/4T) and quarters platform (2/4Q). Crude oil export was through offshore buoy loading and gas was either injected or flared. A subsequent phase included the installation of export pipelines for oil and gas and further facilities for processing (2/4T), export of crude oil (2/4P) and export of gas (2/4R). Export of crude oil commenced in 1975 and gas in 1977. Parallel activities included the development of most other fields in the Production License 018 area all which were tied into the central processing and transportation facilities at the Ekofisk Field. The West Ekofisk and Cod Fields came on stream in 1997, the Tor Field in 1978, the Albuskjell, Eldfisk and Edda Fields in 1979 and the Embla Field in 1993. Several third party fields have also been tied into the central facilities at Ekofisk for processing and/or transportation. This includes the Ula and Gyda Fields operated by BP, the Tommeliten Field operated by Statoil, the Valhall and Hod Fields operated by Amoco and Norsk Hydro's Mime Field (now shut down).