Tarraco Field Development With The SALS Floating Production System
Authors: Eijkhout F. 
Published: December 2007

A floating production system including a single anchor leg mooring system (SALS) was installed in the Tarraco concession (Castellon), in the Mediterranean offshore Spain and taken into production by Shell Espana on 8 August, 1977.

This paper gives a description of the system and also of its design, construction and field installation.

Operational experience with the floating production system during the first 10 months is also reviewed.

Introduction

In June, 1976 Shell Espana drilled a discovery oil well, Castellon B-5, in the Tarraco production concession in the Mediterranean off Tarragona in 117 a waterdepth.

The discovery could only be rated marginal and since it was located fairly distant from shore it was obvious that this field could not be developed economically with the conventional platform and pipeline to shore method. Various schemes were evaluated and the SALS floating production system finally selected.

The system, shown in Fig. 1 consist of:an underwater completed wella 60,000 Ton DWT tanker with process and storage facilities, permanently moored by means of aSALS. This single point mooring system allows the tanker to weathervane seeking the position of least resistance to wind, waves and current.

The process and well control equipment and also the facilities for wireline workover operations are installed on the deck of the tanker. The well is produced into the process facilities through a 4 inch Coflexip flow line. Produced oil is stored in the tanker whilst separated gas is burned in incinerators and under the ship's boilers. The crude is periodically lifted with a shuttle tanker.

The SALS production system was originally conceived by SBM Inc. and further developed with Shell Internationale Petroleum Mij. for the Tarraco field development, in close consultation with the classification societies Lloyds and Bureau Veritas. It was designed, fabricated and installed in 11 months time from the go-ahead date. It includes several new features the principal ones being: separation and gas disposal facilities on the tanker's deck and facilities to burn associated gas under the ship's boilers.

Particular attention has been paid to realize an operationally safe production system.

General System Description

Underwater Completion, Controls and Workover Facilities

The discovery well was completed underwater by the same drilling unit 'STAFLO' that had also originally drilled this well.

The downhole completion arrangement includes a production packer and 5 inch tubing with a surface controlled subsurface safety valve installed near the top of the string.

The completion above seabed level includes from bottom upward: a hydraulic operated (Wellhead) connector; a tubing head spool; the X-mas tree with flowline outlet (see fig. 2). It is simple and very similar to the 15 oilwell and dump flood completions that were made in the Persian Gulf and in the South China Sea between 1968 and 1973.

Underwater Completion, Controls and Workover Facilities

The discovery well was completed underwater by the same drilling unit 'STAFLO' that had also originally drilled this well.

The downhole completion arrangement includes a production packer and 5 inch tubing with a surface controlled subsurface safety valve installed near the top of the string.

The completion above seabed level includes from bottom upward: a hydraulic operated (Wellhead) connector; a tubing head spool; the X-mas tree with flowline outlet (see fig. 2). It is simple and very similar to the 15 oilwell and dumpflood completions that were made in the Persian Gulf and in the South China Sea between 1968 and 1973.