GB1595529A

GB1595529A - Control system for subsea oil well heads

Info

Publication number: GB1595529A
Application number: GB12537/78A
Authority: GB
Original assignee: Tecnomare SpA
Current assignee: Tecnomare SpA
Priority date: 1977-04-01
Filing date: 1978-03-30
Publication date: 1981-08-12
Also published as: FR2385887B1; DK138578A; FR2385887A1; CA1109783A; IT1071925B; NL7803402A; JPS53123302A; DE2813768B2; DE2813768C3; DE2813768A1; NO781093L

Description

(54) CONTROL SYSTEM FOR SUBSEA OIL WELL HEADS (71) We, TECNOMARE S.p.A., an Italian company, of S. Marco, 2091, Venezia, Italy, do hereby declare the invention for which we pray that a patent may be granted to us, and the method by which it is to be performed, to be particularly described in and by the following statement: This invention relates to a control system for use in controlling a subsea oil well head.

According to the present invention, there is provided a submersible control system for use in controlling a subsea oil-well head, the system comprising (a) an electricallypowered hydraulic unit adapted to be hydraulically-connected to the valves of the oil-well for actuation thereof; (b) an electrical circuit including means adapted to receive command signals transmitted (i) acoustically through sea water and/or (ii) electrically along a cable or along an oil flow pipe, the electrical circuit being electrically connected to the hydraulic unit so as to be capable of controlling the operation of the hydraulic unit in response to the command signals; (c) an electrical power generator and means for supplying the generated electrical power from the generator to the hydraulic unit and to the electrical circuit; and (d) a unit for interconnection of hydrualic lines for control from the surface with hydraulic lines for control from the electrically-powered hydraulic unit.

The system according to the present invention does not require frogmen for its erection and operation. It can be remotely controlled both acoustically and by cable and also by electrical signals sent along the pipe lines for the oil. It can be fed with electrical power from a subsea radio-isotope generator.

The control system of the invention may form part of a modular system consisting of a lower module and an upper module, the lower module consisting of components which are intended to stay on the sea bed for a long period of time and the upper module being a control system of the invention (and consequently consisting of components which require occasional upkeep).

The well-head, since the control system is integrated thereon, does not require any connection to the terminal platform, apart from pipe lines for the oil (and apart from, possibly, a cable for transmitting the command signals). In this way, the problems associated with the use of subsea electric power cables and connectors are avoided.

The electrical circuit preferably includes (i) means adapted to transmit acoustic signals through sea water, and/or (ii) an alarm system for automatically closing the valves of the well in the event of (a) damage to the system of remote transmission or to the feed system. (b) an irregular condition of operation of the well, (c) a break in an oil flow pipe, or (d) a lack of propagation of the acoustic signals. The electrical circuit is preferably adapted to actuate simultaneously a number of subsea well heads in the event of alarm conditions on the surface platform.

The hydraulic unit is preferably housed in a steel container partitioned into two chambers by a plate through which are formed all of the passageways required for electrical and hydraulic interconnection both between the two chambers and between either chamber and the exterior. The hydraulic components of the hydraulic unit, including a hydraulic pump, are preferably housed in one of the two chambers, this chamber being pressure compensated and immersed in oil. Preferably, the hydraulic unit includes two hydraulic circuits, namely a high-pressure circuit and a low-pressure circuit, fed by the same hydraulic pump.

The hydraulic unit preferably includes a safety system for the automatic release of hydraulic pressure from the actuators of the valves of the well to close the well in the event of (a) damage to the feed system, (b) irregular pressure conditions in the well, (c) damage to the remote transmission system, or (d) defective reception of the command signals.

The control system is preferably constructed in the form of a module, and adapted to be used on well heads differing in the number of valves to be actuated and to be calibrated for different operative conditions.

The electrical power generator is preferably an electrical power generator of low electrical power output, e.g. a radio-isotope generator.

The control system is preferably adapted for use in sea water of a depth of up to 600 metres.

For a better understanding of the invention, reference will now be made, by way of example, to the single figure of the accompanying drawing, showing a control system of the invention.

The control system includes a housing 1 for control electronic circuit, connected to hydrophones and to a transmitting station for receiving and sending acoustic signals.

The control circuit may instead be adapted to receive and send electrical signals transmitted by electric cable and subsea conduits.

The control circuit encodes the signals received from the well head and decodes the signals sent to the well head.

The control circuit is adapted to operate the cut-off valves for the well (via an intermediate electrically-powered hydraulic unit in a housing 2), to send analogic data (inter alia pressure readings and electric voltage readings), to send signals giving the position of the cut-off valves of the well, and to send alarm signals (including signals indicating a blockage of the well).

The control circuit is connected to the hydraulic unit contained in the housing 2.

The housing is partitioned into two chambers which are mutually connected by an interconnecting plate through which are formed passageways for electrical and hydraulic interconnection both between the two chambers and between either chamber and the outside. These interconnections are used, inter alia, for actuating valveoperating members, for identifying their position, and for reading the pressure in the well-head.

In the top chamber, under atomospheric pressure, is housed an interface unit along with storage batteries for feeding power both to the hydraulic unit and to the control circuit. The interface unit controls the starting and stopping of an electric motor which drives the hydraulic unit, on the basis of signals given by pressure-stats installed on the hydraulic accumulators (all of the electric signals from the hydraulic unit and from the apparatus mounted on the well head are sent to the control circuit, and vice versa).

In the lower chamber, which is pressurecompensated and is thus under a pressure the same as that at the well head, the hydraulic unit and its electric motor are enclosed in an oil-bath. The electric motor actuates a pump which is intended to load appropriate hydraulic accumulators.

The hydraulic accumulators actuate the actuators for the cut-off valves of the well at the instant of time at which cut-off is required and within the times which are provided for actuating such valves. The transfer of hydraulic fluid to the actuators takes place by directional electromagnetic valves which are controlled by the control circuit.

A radio isotope generator 3 supplies the necessary electric power to the entire system via the storage batteries installed in the top chamber of the housing 2.

For controlling the valves in the well head during operation from the surface, there is provided a cut-off block 4 which enables the hydraulic system installed on the well head to be cut off by appropriate hydraulicallyactuated valves.

WHAT WE CLAIM IS: 1. A submersible control system for use in controlling a subsea oil-well head, the system comprising (a) an electricallypowered hydraulic unit adapted to be hydraulically-connected to the valves of the oil-well for actuation thereof; (b) an electrical circuit including means adapted to receive command signals transmitted (i) acoustically through sea water and/or (ii) electrically along a cable or along an oil flow pipe. the electrical circuit being electrically connected to the hydraulic unit so as to be capable of controlling the operation of the hydraulic unit in response to the command signals; (c) an electrical power generator and means for supplying the generated electrical power from the generator to the hydraulic unit and to the electrical circuit: and (d) a unit for interconnection of hydraulic lines for control from the surface with hydraulic lines for control from the electrically-powered hydraulic unit.

2. A control system as claimed in claim 1, wherein the electrical circuit includes means adapted to transmit acoustic signals through sea water.

**WARNING** end of DESC field may overlap start of CLMS **.

Claims

**WARNING** start of CLMS field may overlap end of DESC **. one of the two chambers, this chamber being pressure compensated and immersed in oil. Preferably, the hydraulic unit includes two hydraulic circuits, namely a high-pressure circuit and a low-pressure circuit, fed by the same hydraulic pump. The hydraulic unit preferably includes a safety system for the automatic release of hydraulic pressure from the actuators of the valves of the well to close the well in the event of (a) damage to the feed system, (b) irregular pressure conditions in the well, (c) damage to the remote transmission system, or (d) defective reception of the command signals. The control system is preferably constructed in the form of a module, and adapted to be used on well heads differing in the number of valves to be actuated and to be calibrated for different operative conditions. The electrical power generator is preferably an electrical power generator of low electrical power output, e.g. a radio-isotope generator. The control system is preferably adapted for use in sea water of a depth of up to 600 metres. For a better understanding of the invention, reference will now be made, by way of example, to the single figure of the accompanying drawing, showing a control system of the invention. The control system includes a housing 1 for control electronic circuit, connected to hydrophones and to a transmitting station for receiving and sending acoustic signals. The control circuit may instead be adapted to receive and send electrical signals transmitted by electric cable and subsea conduits. The control circuit encodes the signals received from the well head and decodes the signals sent to the well head. The control circuit is adapted to operate the cut-off valves for the well (via an intermediate electrically-powered hydraulic unit in a housing 2), to send analogic data (inter alia pressure readings and electric voltage readings), to send signals giving the position of the cut-off valves of the well, and to send alarm signals (including signals indicating a blockage of the well). The control circuit is connected to the hydraulic unit contained in the housing 2. The housing is partitioned into two chambers which are mutually connected by an interconnecting plate through which are formed passageways for electrical and hydraulic interconnection both between the two chambers and between either chamber and the outside. These interconnections are used, inter alia, for actuating valveoperating members, for identifying their position, and for reading the pressure in the well-head. In the top chamber, under atomospheric pressure, is housed an interface unit along with storage batteries for feeding power both to the hydraulic unit and to the control circuit. The interface unit controls the starting and stopping of an electric motor which drives the hydraulic unit, on the basis of signals given by pressure-stats installed on the hydraulic accumulators (all of the electric signals from the hydraulic unit and from the apparatus mounted on the well head are sent to the control circuit, and vice versa). In the lower chamber, which is pressurecompensated and is thus under a pressure the same as that at the well head, the hydraulic unit and its electric motor are enclosed in an oil-bath. The electric motor actuates a pump which is intended to load appropriate hydraulic accumulators. The hydraulic accumulators actuate the actuators for the cut-off valves of the well at the instant of time at which cut-off is required and within the times which are provided for actuating such valves. The transfer of hydraulic fluid to the actuators takes place by directional electromagnetic valves which are controlled by the control circuit. A radio isotope generator 3 supplies the necessary electric power to the entire system via the storage batteries installed in the top chamber of the housing 2. For controlling the valves in the well head during operation from the surface, there is provided a cut-off block 4 which enables the hydraulic system installed on the well head to be cut off by appropriate hydraulicallyactuated valves. WHAT WE CLAIM IS:

1. A submersible control system for use in controlling a subsea oil-well head, the system comprising (a) an electricallypowered hydraulic unit adapted to be hydraulically-connected to the valves of the oil-well for actuation thereof; (b) an electrical circuit including means adapted to receive command signals transmitted (i) acoustically through sea water and/or (ii) electrically along a cable or along an oil flow pipe. the electrical circuit being electrically connected to the hydraulic unit so as to be capable of controlling the operation of the hydraulic unit in response to the command signals; (c) an electrical power generator and means for supplying the generated electrical power from the generator to the hydraulic unit and to the electrical circuit: and (d) a unit for interconnection of hydraulic lines for control from the surface with hydraulic lines for control from the electrically-powered hydraulic unit.

3. A control system as claimed in claim

1 or 2, wherein the electrical circuit includes an alarm system for automatically closing the valves of the well in the event of (a) damage to the system of remote transmission or to the feed system, (b) an irregular condition of operation of the well, (c) a break in an oil flow pipe, or (d) a lack of propagation of the acoustic signals.

4. A control system as claimed in any of claims 1 to 3, wherein the electrical circuit is adapted to actuate simultaneously a number of subsea well heads in the event of alarm conditions on the surface platform.

5. A control system as claimed in any of claims 1 to 4, wherein the hydraulic unit is housed in a steel container partitioned into two chambers by a plate through which are formed all of the passageways required for electrical and hydraulic interconnection both between the two chambers and between either chamber and the exterior.

6. A control system as claimed in claim 5, wherein the hydraulic components of the hydraulic pump, are housed in one of the two chambers, this chamber being pressure compensated and immersed in oil.

7. A control system as claimed in claim 5 or 6, wherein the hydraulic unit includes two hydraulic circuits, namely a highpressure circuit and a low-pressure circuit, fed by the same hydraulic pump.

8. A control system as claimed in any of claims 5 to 7, wherein the hydraulic unit includes a safety system for the automatic release of hydraulic pressure from the actuators of the valves of the well to close the well in the event of (a) damage to the feed system, (b) irregular pressure conditions in the well, (c) damage to the remote transmission system, or (d) defective reception of the command signals.

9. A control system as claimed in any of claims 1 to 8, constructed in the form of a module, and adapted to be used on well heads differing in the number of valves to be actuated and to be calibrated for different operative conditions.

10. A control system as claimed in any of claims 1 to 9, wherein the electrical power generator is an electrical power generator of low electrical power output.

11. A control system as claimed in claim 10, wherein the electrical power generator is a radio-isotope generator.

12. A control system as claimed in any of claims 1 to 11, the system being adapted for use in sea water of a depth of up to 600 metres.

13. A control system for a subsea oilwell head, substantially as hereinbefore described with reference to the accompanying drawing.