Classifications

• • E—FIXED CONSTRUCTIONS
  • E21—EARTH OR ROCK DRILLING; MINING
  • E21B—EARTH OR ROCK DRILLING; OBTAINING OIL, GAS, WATER, SOLUBLE OR MELTABLE MATERIALS OR A SLURRY OF MINERALS FROM WELLS
  • E21B33/00—Sealing or packing boreholes or wells
  • E21B33/02—Surface sealing or packing
  • E21B33/03—Well heads; Setting-up thereof
  • E21B33/035—Well heads; Setting-up thereof specially adapted for underwater installations
  • E21B33/0355—Control systems, e.g. hydraulic, pneumatic, electric, acoustic, for submerged well heads

Definitions

• the present invention relates to a system for the control and monitoring of surface or subsea hydrocarbon production, comprising production equipment to which is supplied hydraulic power and electrical power and signals for the control of valves etc. and the monitoring of signals from sensors etc., respectively, said hydraulic power and electrical power and signals being supplied from a fixed or floating monitoring installation.
• the invention relates to special signal and power transmission methods for usage in both subsea and surface located control and/or monitoring systems.
• the power transmission method requires a device for storage of energy 5 which comprises a part of the system.
• the energy transfer efficiency will be further increased by sending the power as square waves.
• Such a power storing device which is in fact an accumulator when loaded, greatly improves the utilization of the power in the system. The latter is also another 0 significant advantage with the present signal/power transmission method.
• Fig. 1 is a sketch illustrating a subsea oil production installation and a control and monitoring installation 35 having hydraulic and electrical connections therebetween.
• Fig. 2 illustrates in more detail the equipment associated with the installation shown in Fig. 1.
• Fig. 3 is a diagram illustrating the use of filters in connection with the power suply to the equipment.
• Fig. 4A is a power/signal scematic diagram of a conventional system of signal/power frequency multiplexing.
• Fig. 4B is a power/signal scematic diagram of an embodiment of the present signal/power time multiplexing technique.
• Fig. 5 illustrates an embodiment of a solenoid arrangement and switch arrangement in matrix format.
• the control of valves 5 etc. and the monitor ⁇ ing of signals from sensors 4 etc. is performed from a control room 2.
• the control room 2 is usually manned and situated either at a nearby fixed or floating platform 2a onshore. Under many conditions, in particular at medium and large water depths, the power to operate the subsea valves 5 will be supplied through hydraulic fluids under pressure. The hydraulic energy is supplied through one or more hoses or pipes 3.
• a control unit 1 is positioned locally at the subsea installation 1a to distribute pressure to or from actuators 13 which control the valves.
• the control unit 1 also receives, magnifies and codes signals from the subsea installation 1a and transfer these to the control room 2.
• the control unit 1 receives control signals from the control room 2 through a cable 3a which contains electrical conductors.
• Control systems of the described type consist of a surface part and a subsea part connected by cables, see Fig. 2.
• the subsea part 1a contains a control unit 1 which has an hydraulic section 6 and an electrical 7 section.
• the hydraulic energy is supplied to the hydraulic section 6 where the hydraulic pressure is distributed to the different actuators 13 by opening and closing hydraulic valves.
• the hydraulic valves are operated by electromagnets (hereafter referred to as solenoids) which are supplied by electrical signals from the electrical section.
• conduits may be bundled in a single electro-hydraulic cable or in two or more separate cables.
• the present invention provides a combination of three aspects which used together result in considerable ad ⁇ vantages relative to the control of subsea hydrocarbon production wells or other subsea production equipment.
• the advantages involve reduced space requirements, reduced weight of the equipment, and a simpler and less expensive control system.
• the present invention makes it possible to supply power at low voltages. This is an advantage, as all usual organic insulation materials tend to get saturated when in use in subsea environment. Low voltages can be transmitted even through saturated cables without excessive losses. Low voltages have the further advantages of reducing the risk of corrosion as compared to the usual systems.
• the signals for control and monitoring are transmitted through the same cables as the electric power. This is achieved by sending the control signals in certain time intervals.
• the method is called time multiplexing. In periods when no signal transmission is required an un-interrupted power supply can be maintained.
• the electrical power received by the control unit is stored in an internal condensator. The result is that power pulses of sufficient high effect can be transferred to the solenoid valves, while the power supply through the cable can be transferred over time at a low voltage.
• the consequence is that the power supply cables become redundant, as all power supply to the subsea electronics may be transmitted through the signal cables.
• a pluraily of valves can be controlled via a single pair of conductors by transmitting several signals of different frequencies simultaneously.
• the electric power is supplied on a low frequency.
• the signals are transmitted by a so-called frequency multiplexing, whilst the power and signals are separated by so-called time multiplexing, whilst the power and signals are separated by so-called time multiplexing.
• a third characteristic aspect of the invention constitute the solenoid valves in the subsea control unit located in matrix arrangement relative to the lines through which electric power will be supplied.
• a control system based on the invention will comprise a subsea control unit 1 and two main computers 8 located in the control room 2 on the surface.
• a cable 15 links the control unit 1 and one of the main computers 8 in the control room 2.
• the main computer 8 is provided with a lockable panel from which the well actuators can be controlled and from which signal transmitters for pressure and temperature can be recorded.
• the main computer is also provided with an interface to which a smaller computer of standard type may be connected for control and monitoring of signals via keyboard 8a and visual display unit 9.
• the subsea control unit 1 may, according to the invention, comprise an electronic canister 7 containing microprocessor based electronics 16 for receiving, conditioning and transmitting signals. Signals from the control room 2 are transmitted via the signal cable 15 to the electronic canister 7 where the microprocessor based electronics interprets the signals in such a way that the electrical power stored in the capasitor 17a is directed to the desired solenoid valve 14 in order for the valve to trigger and open for the provision of hydraulic fluid and pressure.
• the signals from the supplied electronical power are separated using a filter 11 in conjunction with the electronics power supply 9.
• a filter 12 is also located on the surface unit. The power is converted to direct current and stored in a capacitor 17a.
• the signal cable 15 conducts electric alternating current of a moderate voltage level, typically 24 volts.
• a possible format of the alternating current in the cable is, according to the invention, an interval of low frequency current 13.
• a typical frequency may be 50 Hz.
• the power supply will be switched off and signals 14 transmitted on a somewhat higher frequency.
• a typical value for frequency transmission may be in the range of 1000 to 1300 Hz.
• the solenoid valves 14 in the subsea control unit 1 are triggered by power pulses to the valves solenoid 19.
• the transfer of power to the solenoid 18 coils is by electronic switches 17, see Fig. 5, closing the circuit to the coils 18.
• the connection between solenoids 19 and switches 17 are arranged in the form of a matrix such that two switches must be closed in order for the electric circuit to be completed. Every single solenoid has two associated switches.
• the switches 17 are arranged in two groups. One of the solenoids leads 1-n corresponds to a first group of switches 1n-1nm. The other lead corresponds to the second group column of switches 1m-1nm. In this way only one selected pair of switches will close the circuit to one particular solenoid valve and to this only. The arrangement will reduce the necessary number of switches.
• Fig. 5 there is also illustrated a typical solenoid arrengement, i.e. a solenoid 19 connected between a positive column driver and a negative row driver, with an arc suppressor diode connected therebetween.
• a typical solenoid arrengement i.e. a solenoid 19 connected between a positive column driver and a negative row driver, with an arc suppressor diode connected therebetween.
• the need for separate power supply cables is eliminated.
• the power is supplied through the signal cables.
• Several simultaneously signals may be transmitted through the same conductor by the use of frequency multiplexing.
• Electric power may be transmitted through the same cables by the use of time multiplexing as compared to the signals.
• the number of selector switches is reduced due to a matrix arrangement relative to the solenoid valves to which the power is to be supplied.
• the present invention is different from other known techniques by the fact the the three above aspects are present simultaneously and are used for the control of especially subsea wells.

Landscapes

• Life Sciences & Earth Sciences (AREA)
• Engineering & Computer Science (AREA)
• Geology (AREA)
• Mining & Mineral Resources (AREA)
• Physics & Mathematics (AREA)
• Environmental & Geological Engineering (AREA)
• Fluid Mechanics (AREA)
• General Life Sciences & Earth Sciences (AREA)
• Geochemistry & Mineralogy (AREA)
• Earth Drilling (AREA)
• Arrangements For Transmission Of Measured Signals (AREA)
• Organic Insulating Materials (AREA)

Applications Claiming Priority (3)

Publications (1)

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• 1991
  • 1991-03-20 WO PCT/NO1991/000043 patent/WO1991016523A1/en not_active Application Discontinuation
  • 1991-03-20 EP EP91905871A patent/EP0524952A1/de not_active Ceased
• 1992
  • 1992-10-28 CA CA002081624A patent/CA2081624A1/en not_active Abandoned

Non-Patent Citations (1)

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