In a review of various control system types for floating production facilities, it is quickly seen that most system options have been developed assuming that the operator is hydraulically operated. Direct hydraulic, the various piloted options and acoustic control are well defined in a variety of publications. In this chapter will be described a direct hydraulic control system required by Production Vessel-Test (PV-T), a joint venture formed by Houlder Offshore and North Sea Terminals. The intent of this chapter is to optimize one parameter - the cost.
The earliest example of floating production control of a(Fig. 1 is available in full paper) subsea well is on the Castellon ?B? project offshore Spain, as shown in Fig. 1. Direct hydraulic control of a single well causes production fluids to flow through the single-anchor leg system (SALS) to the storage tanker.
Since then, there has been an increase in the complexity of the subsea architecture, notably the introduction in the Hamilton Brothers Argyll Field of a multiwell development to a semisubmersible floating facility with export system Recent years have seen the development of multiwell multifacility subsea producing to a floating facility; for example, Sun Oil's Balmoral, Amerada Hess Ivanhoe/Rob Roy and the proposed Sovereign Emerald. Where is the next generation system required? The chapter will discuss this.
PV-T is intent on well testing and pilot production. As a contractor, they are intent on having the most simple, robust, reliable system possible The oil price fluctuations in very recent times have shown that for a system to be economic throughout its design life, the overall costs must be minimized in such a way that break-even is reached at a low revenue per barrel produced It is not the intention of this chapter to determine what is a marginal field, only to show methods of reducing capital costs on certain equipment. On that basis, there is a need for a low-cost control System.
Simplicity alone would require this system to comprise a pump, a hose and a ganged connection to all subsea valves. Flexibility of operation would be minimal, but cost and maintainability would be maximized.
A more serious definition of the design premises would be as followed
high operability
low maintenance
simple planned maintenance
low purchase cost
low maintenance cost
does not compromise safety
To expand on the above, the system must be in a working state at all times To achieve high reliability in a complex system involves a high cost: the response to the first design premise in this instance must therefore be simplicity.
Low maintenance in a system echoes the previous statement in that minimization of components and complexity reduces the need for maintenance. Simple planned maintenance requires the designer to keep as much of the system package on the surface and a minimization of hardware on the sea bed at the installation.
