ABSTRACT

The paper reviews the different types of floating production systems available ttt the petroleum industry and addresses why these platforms presently represent attractive candidates for future worldwide offshore field developments. Attention is focused on tension leg platforms monohull production vessels and semisubmersible production platforms. The potential of new concepts such as the Spar platform are mentioned. Further, the paper focuses on important design features and engineering challenges for the various platform types. In order to highlight the global design aspects, both topside facilities and support structures as well as mooring systems, risers, subsea facilities and motion behavior are addressed. References torecent designs are made to illustrate the present state-of-the-art technology.

INTRODUCTION

At present floating production facilities represent strong candidates for offshore field developments in different parts of the world. Extended well testing, early production, wellhead support, full or partial processing and drilling or workover are missions considered for these platforms. Even large field centers have been conceived based on floating system. The attractive merits of floating production systems have been recognised for a considerable period of time. Still there are relatively few units in operation compared to fixed traditional platforms.

Why do we see an increase of interest for such units today?

Several reasons can be given. Attractive capital expenditure and confidence in the technology derived from experience from an increasing number of entities are among the most important factors. Floating production systems are flexible, cost and schedule effective solutions in particular for deep water applications. But they are also well suited for shallow waters and for areas with limited infrastructure. They have demonstrated a high production availability under harsh environmental conditions. Expensive offshore works are limited, as most of the construction, hook-up and commissioning are completed at shore or inshore at significantly less cost. Early positive cash flow can be achieved due to comparatively short development time. Floaters may be installed over pre-drilled wells.

Floating units are also favorable with respect to economical risk exposure. Reduced field abandonment cost and potential residual value due to possible reuse at another location or conversion to other purposes are also part of the considerations.

Floating production facilities will be attractive for prospective field developments gradually moving into deeper waters and in areas with little or no infrastructure. Compared to fixed platforms, the costs of the water depth sensitive platform elements represent a relatively small portion of the total capital expenditure.

Main components of the floating production system are:

  • topside facilities

  • hull

  • station keeping system

  • risers

  • subsea wells

  • flowlines

  • offloading system

Many of these items will be covered in depth in this series of presentations, Hence, the present paper is given a deliberate bias towards the platform and the marine aspects.

INDUSTRY CONFIDENCE

Close to 90 floating production systems have been in operation in different parts of the world. Brazil, the North Sea, Gulf of Mexico and South East Asia have been the dominating regions so far. As depicted in figure 1, most of these unitshave been monohull production vessels or semisubmersibles, mainly conversions.

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