This paper provides a brief introduction to the modern electro-hydraulic multiplexed control systems used when operating drilling and production equipment in the development of deep water hydrocarbon reservoirs The differences between drilling and production control systems are then discussed in terms of the differing functional requirements of the two sorts of system and the technical and economic factors which have lead the development of future systems Ongoing development work for both future subsea production and drilling control systems is then discussed


This paper discusses future developments of subsea control and instrumentation systems to meet the Oil Industry's ongoing need to operate both subsea drilling and production systems at increasingly deeper water depths. Whilst addressing possible future developments, the author has restricted this discussion to those concepts which are currently under development - the art-of-the-possible in ten year's time will be a different story

In the continued search for hydrocarbons, exploration and production operations are moving increasingly further offshore and into increasingly deeper water For our purposes, deep water can be defined as in excess of 1000 m It has been demonstrated that current technology can operate at these depths, however moving into yet deeper water will impose increased difficulties and alternative technologies may become technically and economically more attractive than the current solutions It is these technologies, and the reasons for their development, that are addressed here

This paper starts by considering modem subsea control systems and then examines the driving factors for future system developments by comparing the functional needs of both drilling and production systems The author's perception of likely future developments in production and drilling systems is then presented and discussed


Modem subsea control systems are generally electro-hydraulic multiplexed (EH-Mux) systems, whereby hydraulic power is generated at the surface and transmitted to one, or more, subsea control pods by means of an umbilical In essence, a control pod comprises of a number of solenoid-operated hydraulic pilot valves such that the hydraulic fluid may be directed to the various hydraulic actuators which control the relevant subsea equipment (valves, rams, chokes etc)

Where larger volume flow rates are required to operate actuators - typically in drilling control systems - additional hydraulically piloted valves may be used such that the solenoid valve controls flow to the pilot stage of the valve which in turn controls the supply of high pressure fluid to the actuator The electrical control signals for the solenoid valves are transmitted from the surface via a multiplexed signal channel and de-multiplexed and error-checked within the subsea electronics package In addition to transmission and confirmation of control signals, the two-way multiplexed link allows system status information and subsea instrumentation read-back data to be transmitted to the surface from the pod

Figure1 illustrates the schematic form of a generic electro-hydraulic multiplexed control system Such systems have replaced earlier direct hydraulic systems as increased umbilical lengths, due to increased step-distances and greater depths, have resulted in unacceptably long hydraulic response times

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