Abstract

The fleet of FPSOs and FSOs has been growing in the last years and is expected to grow more quickly in the coming years. The reason for fleet growth are the deep-water production, the increasing number of offshore fields that are being discovered and the need for fast-track development. The present fleet of FPSOs is composed by more than 65% of converted units and the fleet of FSOs is almost 100% of converted units. The conversion of an existing tanker into an FPSO or FSO is, in most cases, more economical and takes less time than a newbuilding. There are several factors that should be considered in a FPSO or FSO conversion to have a successful project. Based in the experience gained in the successful conversion of four FPSOs and FSOs for the deepwaters of Campos Basin - Brazil, several aspects that should be considered in the design for a conversion of a tanker into an FPSO or FSO are described. Critical issues like the selection of the vessel to be converted, project start up structural design installation of large capacity production processing facilities will be addressed.

Introduction

The fleet of FPSOs and FSOs has been growing in the past years and is expected to grow more quickly in the coming years. The reasons for the fleet growth are the deep-water production, the increasing number of offshore fields being discovered and the need for fast-track development. The main advantages of FPSO utilization includes:

  • Integration of several functions in one vessel;

  • Large deck area;

  • Small variations of draft due to weight of production processing facilities;

  • Flexibility in the vessel selection;

  • Simple construction;

  • Reduced investment cost;

  • Short time schedule;

  • Easy decommissioning after completed field production.

The conversion of an existing tanker into a FPSO is, in most cases, more economical and takes less time than a newbuilding FPSO.

Nevertheless a FPSO cannot be considered as a tanker with a different payload, that is the production processing facilities. The function of a FPSO is totally different from the function of a tanker in many aspects of design, conversion/construction and operation. The proper understanding of the function of FPSO is an essential element for the successful design and conversion/construction.

The FSO is less complex than an FPSO but, except for small vessels in shallow waters, cannot, also, be considered as a tanker. In deep waters and harsh environments the mooring and offloading systems and the need to stay on site for periods as long as 20 years are responsible for significant modifications in the vessel.

The intent of this paper is to discuss some aspects of FPSO and FSO conversion design for installation in deep waters and mainly related to the vessel.

The FPSO Fleet

The present FPSO fleet is composed of about 80 vessels, with about 66 vessels in operation and about 14 vessels in conversion or construction, and the FSO fleet is composed of about 80 vessels with about 77 vessels in operation and 3 vessels in conversion.

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