Abstract

Floating concepts for LNG production and LNG terminals are being evaluated by the industry to meet the increasing worldwide demand for LNG as a clean, environment friendly energy source. Novel technical solutions are required to enable commercially viable developments of remote resources, marginal fields, utilization of associated gas and to provide increased terminal capacity. These new concepts involve a large number of technical uncertainties, large investments and large perceived hazards and this requires effective risk management. In response of this DNV has developed a classification approach for LNG FPSOs, aiming at provision of a structured and predictable assessment of novel concepts.

These classification services and rules for LNG FPSOs draw upon the long experience with risk management of gas carriers and oil producing FPSO's. The classification approach utilizes the best practices both with regard to traditional codes and standards, industry practices as well as use of quantitative risk assessments for decision support among technical alternatives, and qualification procedures for new designs.

Introduction

The demand for natural gas is increasing on a world-wide basis as a result of the increase in the worlds energy consumption, and environmental concern.

Among the fossil fuels available today, natural gas is by far the most clean and environmentally friendly energy source. LNG represents today the most efficient commercial handling and long distance transportation of natural gas.

Floating production of LNG will allow development of remote gas fields and utilisation of associated gas from oil production. Several concepts have been developed recent years concluding feasibility from an economical, technical and safety point of view.

Common to these concepts are that they represents new solutions which not yet have been proven in practice. The following issues represents particular challenges both with respect to the safety for personnel, vessel as well as functional requirements:

  • A highly complex and compact process plant installed in a limited area.

  • Storage of LNG in the proximity of Process equipment and Accommodation.

  • Cargo Transfer in open seas.

Key objectives in the design must be to

  • ensure reliable operation.

  • offer adequate protection of personnel including means to ensure safe evacuation and escape.

  • minimize the risk for massive release of LNG from the cargo tanks which can develop into catastrophic scenarios resulting in total loss.

The latter implies that focus must be given to all events with the potential to damage the tanks e.g.

  • escalation of process events to the storage tanks (fire, explosions, dropped objects)

  • tank integrity

  • collisions

  • hull damage, flooding and stability

DNV has identified LNG FPSOs to be an area where we can contribute to our customers needs and demands and we have developed new rules for the Floating LNG/LPG Production storage and offloading units. For this purpose a new class notation was launched in 2001.

This content is only available via PDF.
You can access this article if you purchase or spend a download.