This chapter describes the result of the detailed design stage of a development programme undertaken jointly by Vetco Gray, as a designer and manufacturer of subsea production systems, and Comex Houlder as designer and operator of remote intervention systems Supported by eight oil companies and the EEC, the project is proceeding and the designs presented here are currently being manufactured. A full testing programme is scheduled for July 1989. A unique feature of the programme and the design is that it is derived by a team incorporating the manufacturer and designer of subsea production systems (Vetco), the operator of the remote intervention system (Comex Houlder), and most important, the operators of the equipment who are charged with keeping the subsea equipment operating (1.e the oil companies) The initiative for the programme was taken by Comex Houlder and Vetco Gray and they have led the design. However, this has been subject to continuing input and audit by the oil companies, whose direct experience of actually operating and maintaining subsea systems has been fundamental to the success of the design. The technical description given in this chapter is a very brief overview of the developed system. Further information is available from the authors.

THE ECONOMICS OF REMOTE INTERVENTION MAINTENANCE IN DIVER WATER DEPTHS

The impetus for this development programme was not the need to produce in deep water. The justification of the programme was the reduction in field operating costs and reduction in lost production which it was believed could result from designing subsea production equipment on an integrated basis with maintenance systems to be used to intervene on it remotely The economics of remote intervention have been addressed elsewhere (Ref. 1). Depending on the type of subsea development involved, this analysis showed that the internal rate of return (IRR) for a field development could be measurably improved by replacing the diver with remote methods during the operational phase of field development.

The designs produced in the current programme have shown that subsea production system can be designed to maximize remote intervention with only a marginal cost increase over equipment which will not allow remote intervention Feeding this result into the analysis undertaken in Ref. 1 shows that the use of remote intervention for the type of field development considered (Fig. 1) can improve the IRR by up to 3%

The improvement derives from three factors: the capital savings resulting from not having to install a dive system on the floating production platform, the lower cost of ROV support vessels as opposed to diving vessels, and the reduced amount of lost production due to failure of tree-based equipment and length of time to mobilize and carry out an intervention. The effect of each of these is debatable, but whatever the amounts, the overall result is an improvement in the internal rate of return of approximately 3%. This may not be seen as large, but together with savings to be made by technical improvements in other.

Fig. 1 Hypothetical field development.(available in full paper)

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