Novel Cost Effective Installation Approach for a Marginal Field. The Lufeng 22-1 Field Development in China.
Authors: Pillai Sitham 
Published: October 2008

This paper discusses the installation approach taken to help realize the development of a marginal field, the Lufeng 22-1 field offshore China. The paper covers the view of an installer on how proven Norwegian diverless technology has been simplified and transferred to a new region in the world. The paper describes the ideal installation ship concept which has a combined capability to install mooring systems, flowlines1 risers/umbilicals, perform medium lifts and diverless tasks. This is the spread concept for the future to make remote marginal field developments viable using FPSO technology.

Introduction

The Lufeng 22-1 field is a small oil field located offshore China in the South China Sea, south-east of Hong Kong, in a water depth of 333 meters. This field discovered in 1986 is marginal (ref. 1) in nature.

The size of the reserves together with the waxy nature of the crude, the water depth, environmental conditions and the remoteness of the field from an existing infrastructure have made the realization of this development difficult.

Advances and experiences gained in subsea technology coupled with the use of Floating, Production, Storage and Offloading (FPSO) technology has enabled the deeper offshore fields to be developed in a more cost effective manner compared to the use of conventional platforms which sit on the seabed.

In addition to the above, the market has recently changed with the availability of FPSO's for lease on a short term basis (typically a minimum of 2 years). These factors coupled with the current oil price have lead to the feasibility of developing the smaller deep water fields. In the case of Lufeng 22-1, the Lufeng Development Company (LDC), a Norwegian registered consortium comprising of Statoil Shipping and Maritime Technology, Advance Production Systems DA and Stolt Comex Seaway Ltd. have contracted to undertake the development for the operator Statoil Orient Inc. (SOI).

LDC will lease the FPSO to the operator for a minimum duration of 2 years, with 5 year options, and provide the flexible dynamic risers and the subsea installation (excluding the production template) on a lump sum basis.

Subsea Layout

The development of the field comprises of the following main elements:AFPSO.A submerged turret production buoy with its associated six leg mooring system.A 5 slot template.Subsea artificial lift booster pumps.Two ? 7" flexible production risers, a control umbilical and a power supply umbilical.

Figure 1 : Lufeng 22-1 Field Development Arrangement

At the very start of the project, both SO1 and LDC worked closely to evaluate possible development scenarios. Two basic scenarios were evaluated as follows:Scenario 1 - the placement of the FPSO directly above the subsea template thus enabling the subsea artificial lift booster pumps to be changed out from the FPSO without having to shut down production.Scenario 2 - the placement of the FPSO some 1-2 km away from the subsea template. This scenario has the advantage that drilling and well completion can be carried out simultaneously with the offshore installation of the FPSO related equipment and associated risers, flowlines and umbilicals.