Subsea Production Systems - Improve Cost Efficiency and Further Reduce Cost per Barrel Produce
Authors: Rosnes J. , Lindland H.J. , Inderberg O. 
Published: October 2008

Today, Statoil has a number of subsea wells in production, has several ongoing projects, and has a number of promising prospects where the use of subsea wells will be essential for an economical sound development. These fields range from the development of the Norwegian Asgard and Gullfaks Satellite fields which include a large number of wells, complex reservoirs, and have a long field life, to small international fields like the Lufeng (offshore China) and Connemara (offshore Ireland) fields which include few wells, have a short field life, amd are very marginal developments.

The paper reviews Statoil's and KOS's experience and ongoing work with subsea production systems, and address strategic activities taken to cover needs related to the development of smaller fields in the coming five year period. The paper focuses on the preparations which Statoil and KOS/FMC have undertaken to enable fast-track field developments. Essential in this is to remove the delivery of the subsea Xmas trees and other long lead items from the critical line of a field development.

Flexibility and standardisation are key issues and the paper outlines how Statoil and KOS/FMC have focused on these when establishing low cost building blocks for international fast-track developments.

The paper decribes how building blocks have been developed; both for the marginal subsea developments where low expenditure and risk are more important than maximising system availability, and for subsea developments with enough recoverable reserves to allow oil production to be optimised and the recovery factor to be maximised to a larger extent.

The paper concludes that it is essential to undertake the preparatory work which is outlined in this paper in order to be able to improve cost efficiency and further reduce cost per barrel produced.

Introduction

Statoil has completed or placed equipment orders for about 150 subsea wells since Statoil completed its first subsea well on the Gullfaks field 11 years ago. Most of these wells are located in Norwegian waters.

The use of subsea wells as the primary method of producing hydrocarbons has had its final breakthrough on the Norwegian shelf through the large developments Asgard/ Gullfaks Satellites (Operator Statoil) and Troll Oil (Operator Norsk Hydro). Here it has been essential to maximise oil recovery from complex reservoirs.

There will be an increasing need for a cost efficient method to develop smaller, very often marginal fields which typically has a short field life and recoverable reserves in the order of 5 - 15 million Sm3 in the future.

These smaller fields may be marginal for different reasons, but common for them all could be the method of development and the need to find internationally competitive solutions.

The simple conclusion is that standardisation to international suppliers standard products and establishment of a close relationship with a few key contractors through frame contracts could give both fit for purpose low cost equipment and arrangements for short delivery times which would enable fast-tract developments.

Definition of Subsea Systems and Cost Driving Factors

Review of Statoil field development experience.

KOS/FMC has become Statoil's main supplier of subsea production stations.