Girassol: Subsea Well Completion Experience
Authors: Thane Larry , Lassus-Dessus Jean , DeLaporte Dominique 
Published: October 2008

On the Girassol project, an integrated project team was responsible for subsea well completions from conceptual design through to installation. This paper summarizes experiences to date with equipment delivery, installation and early operations including production start-up. Future developments and challenges are discussed with a focus on subsea aspects of well completions. Non-productinve time (NPT) results are presented and analyzed. Examples are given of specific successes and problems.

Introduction

A project life-cycle (Life of Field) approach was taken for Girassol subsea well completions. This approach required consistency and continuity through all project phases: equipment delivery, installation and operations. Trade-offs between these phases must be evaluated and managed.

Subsea well completion equipment and services was supplied as part of a comprehensive lump-sum contract for the Girassol subsea production system (SPS). This SPS package consisted of subsea well equipment (including tooling packages), subsea manifolds, production control systems, workover control systems, and tree-to-manifold jumpers.

Conceptual equipment design was the result of a design competition between four major subsea contractors. Following this design competition, the winning contractor was selected as supplier for the entire SPS package.

Major adjacent, ie interfacing with SPS, contract packages proceeded in parallel with the SPS contract.Drilling rigs (RIG).Downhole well equipment (WELL).Umbilical and flowline (UFL).Floating, production, storage, and offloading (FPSO).

This approach, parallel engineering and manufacture of all contractual packages, was a consequence of the "fast-track" development strategy adopted for Girassol. Total time from SPS contract award to installation of first subsea Xmas tree was 32 months. First oil production was achieved 13 months later. Actual delivery of first xmas tree was 12 months later than planned. This "fast-track" approach posed unique challenges for managing interfaces between contract packages.

The geographical spread of project participants accentuated this challenge. The SPS team was based in Kongsberg, Norway, during equipment design and construction. Subsea well equipment was manufactured, assembled, and tested in Kongsberg and Dunfermline, Scotland. During this time, the drilling team, which was also managing the rig construction, was based initially in Paris, France, and later in Luanda, Angola. The rigs were being constructed in Korea and Brest, France. UFL and FPSO teams were based in Paris. Downhole equipment was manufactured in USA and UK.

The physical location of the Girassol field presented special challenges for subsea well completions. The wellheads are installed in average water depths of 1,400 m, which imposed many design constraints and priorities. The remote location of Girassol, added to the fact that this was the first major subsea development offshore Angola, meant that support capabilities - onshore base, logistics, engineering, spare parts, machine repair, etc - were either distant or had to be established in Angola.

Management of rig NPT during well completions was a critical project objective. This objective drove many strategies, starting from design and continuing through construction and installation.