INTRODUCTION

The subject of this chapter is a floating production system based upon the use of a turret-moored monohull vessel. The functions of this vessel are reflected in its name, COMPASS 2, which is an acronym for Combined Production And Storage System The numeral indicates that this is the second and smaller version of the COMPASS concept.

COMPASS 2 was designed initially for the production of oilfields with small quantities of associated gas (typically gas-oil ratios less than 800scf/BBL). Three types of applications were considered.

  • the production of small fields

  • the early production of large fields

  • the extended production testing of individual wells

For these applications the oil is produced, stabilized and stored on the production vessel before it is exported by shuttle tanker; the associated gas is normally flared or reinjected.

Further to oil applications, the COMPASS 2 concept is now being extended to the production of condensate fields and gasfields. In these cases the surplus hydrocarbon light ends are liquefied instead of being flared or reinjected, with the resulting LNG and/or NGL tankered ashore along with any stabilized oil and condensate. The new vessel is known as CRYOCOMPASS.

In this chapter, consideration is given mainly to the COMPASS 2 vessel as designed for oil applications. The following description presents the conceptual design and marine behaviour of this vessel, how it is moored to the sea bed and connected to the subsea wells, and how it operates. Attention is then given to its cost and economic viability; this is demonstrated by a cost sensitivity analysis of critical parameters such as oil price, rate of exchange, downtime, and capital and operating costs. The third section of the chapter is a short presentation of the CRYOCOMPASS vessel for condensate and gas applications; only limited information is given here on this new vessel, as a full presentation is intended for a later paper.

COMPASS 2: OVERALL DESCRIPTION

The COMPASS 2 vessel is a turret-moored monohull which combines the functions of production, storage and offloading.

With its large oil storage capacity, COMPASS 2 is designed specifically for applications where oil export by pipeline is not available, and is therefore more suitable for oil production than gas production. Oil is exported by shuttle tanker, whereas gas is either flared or reinjected.

For a typical oilfield application, the general arrangement of the COMPASS 2 concept is illustrated in Fig. 1. It consists of:

  • a turret-moored vessel used for both production and Storage

  • a compliant riser system linking the turret on the vessel to a seabed manifold

  • one or several shuttle tankers to export the oil

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