Abstract: A well installation including metallic structure having downhole metallic tubing for conveying product towards the surface, a sub surface safety valve disposed in the downhole metallic tubing for interrupting flow of product towards the surface when closed and allowing flow of product towards the surface when open. Also, valve control means are disposed downhole and arranged for detecting electrical signals in the downhole metallic tubing and for holding the valve open while receiving an electrical signal, and surface signaling means for applying an electrical signal to metallic structure of the well for transmission via the downhole metallic tubing towards the valve control means so as to hold the valve open. The system can be made more robust by ensuring that the control means will only hold the valve open while receiving a signal of given characteristics to help prevent stray currents erroneously holding the valve open.

Abstract: Methods and systems are described for communicating with downhole locations and transmitting power to downhole locations. Use is made of a cable passing someway down into the well. This cable may be connected to a downhole sensor and may be used primarily for communicating with that sensor, but also used in the current techniques described herein. Electrical connection is achieved between the cable and the metallic structure of the well to allow signals to be transferred between the communications tool and the surface via the cable.

Abstract: An aircraft (10) or other conductive body having an electrical conductor which is capable of storing electrical charge, the aircraft comprising: connection means (20, 22, 24) for connecting said conductor with at least one other aircraft (10) having an electrical conductor capable of storing electrical charge so that stored charge can be transferred to and/or received from said at least one other aircraft; and control means (32, 34) for controlling transmission of charge so as to convey information to said at least one other aircraft and/or information extraction means (32, 34) for extracting information from the transmission of charge received from said at least one other aircraft.

Abstract: An aircraft, or other conductive body, (10) comprises transmission means for transmitting information to at least one other aircraft, said transmission means comprising: means (13) for generating an electric field external to the aircraft such that said field can control electrical charge (12) on at least one other aircraft; and means (40) for varying the electric field in accordance with information to be transmitted to said at least one other aircraft so that said at least one other aircraft can determine such information by detection of the control of electrical charge. The conductive body (10) comprises receiver means for receiving information from the transmission means of a similar conductive body, said receiver means comprising: electrical charge storage means (13) for storing electrical charge responsive to control by said transmission means; and detection means (34) for detecting the control of such electrical charge so as to determine information transmitted by said transmission means.

Abstract: Methods of and apparatus for a downhole communication in a well. The well has a metallic structure which includes an insulated metallic, fluid carrying, control line. The method comprises the steps of applying signals to the control line at a first location and extracting the signals from the control line at a second location. There is also provided a downhole communication system for use in a well having a metallic structure. The metallic structure includes an insulated metallic, fluid carrying, control line. The system comprises means for applying signals to the control line at a first location and means for extracting the signals from the control line at a second location. The control line acts as a signal channel. Other methods and apparatus making use of control line carrying no fluid and/or the metallic shielding of cable having insulated metallic shield are also described.

Abstract: A data communication technique for use in producing wells. Signals are transmitted through the product (p) by varying and monitoring flow rate at respective ends of the communication channel. At low data rates robust communication can be provided.

Abstract: Methods and systems for communicating with downhole locations and transmitting power to downhole locations. Use is made of a cable (3) passing someway down into the well. This cable (3) may be connected to a downhole sensor (2) and may be used primarily for communicating with that sensor (2), but also used in the current techniques. Electrical connection is achieved between the cable (3) and the metallic structure of the well to allow signals to be transferred between the communications tool (5) and the surface (4) via the cable (3).

Abstract: A method of operating a downhole component (for example a battery pack) comprising at least one electrolyte based element. The method comprising the steps of locating the component in a downhole environment and whilst the component is in the downhole environment subjecting the element to a pressure in excess of atmospheric pressure to suppress at least one of boiling and evaporation of electrolyte in the element. The component may then be operated at a temperature in excess of that which would be tolerated by the electrolyte based element if not subjected to a pressure in excess of atmospheric pressure.

Abstract: Method systems and apparatus for signalling within pipelines. The systems methods and apparatus make use of a unit locatable within a tubular piece of metallic structure for the transmission and/or reception of signals. The unit includes a magnetic material core (6) which provides a path for magnetic flux through the unit (4). A coil (81) is wound around a portion of the magnetic material core (6) to allow the detection and/or application of magnetic flux in the magnetic core (6). At each end of the core (6) there is pair of arms (63) which are arranged for location adjacent the inside surface of the tubular structure. In use magnetic signals flowing in the tubular structure pass through the core (6) and can be detected via the coil (81) in receive mode and similarly signals flowing in the coil (81) can cause magnetic flux to flow through the core (6) and into the metallic structure in transmit mode.

Abstract: Methods of subsea communication in which a cathodic protection anode is used as a transmitting antenna. The signals are received at a second location by two electrodes which are spaced apart by different distances from the transmitting antenna.

Abstract: Data transmission in pipeline systems A first set of apparatus is arranged for transmitting data from a point in a cased section of a well 1, 3 to a remote location. The apparatus may be used as a relay station 6 to increase operational depth. Signals are applied to and received from the string 1 at the relay station 6 and a selected length of the string 1 is provided with insulating spacer means 9 on either side of the relay station to ensure that the string 1 and casing 3 are effectively isolated for a selected minimum distance. This enables potential differences to be both applied to and detected from the string 1, thus allowing data transmission and reception. A second set of apparatus is arranged for transmitting from an internal unit 408 inside a cased section of the well 401, 403 to the immediate surrounding area outside the casing 403. The internal unit 408 injects current into the string 401. A toroid 415 which surrounds the casing 403 is provided to pick up signals.

Abstract: A subsea navigation system comprising a plurality of spaced antenna means provided on a subsea structure arranged to emit electromagnetic radiation. A detection means is provided on a subsea vehicle for receiving and analyzing the electromagnetic radiation transmitted by the antenna means allowing the subsea vehicle to navigate relative to the subsea structure. Each of the antenna means comprises a cathodic protection anode provided on the subsea structure.

Abstract: A method of operating a downhole component (for example a battery pack) comprising at least one electrolyte based element. The method comprising the steps of locating the component in a downhole environment and whilst the component is in the downhole environment subjecting the element to a pressure in excess of atmospheric pressure to suppress at least one of boiling and evaporation of electrolyte in the element. The component may then be operated at a temperature in excess of that which would be tolerated by the electrolyte based element if not subjected to a pressure in excess of atmospheric pressure.

Abstract: An anode monitoring system for monitoring the integrity of anodes 2 provided on a metallic structure such as a pipeline system 1. A signal circuit Sn including the pipeline 1 and one of the anodes 2 is set up and appropriate signals are looked for at a central station 4. Reception of the signal at the central station 4 is dependent on the integrity of the anode 2 under inspection at that time. If the anode 2 is missing or defective the expected signal is not received and thus the fault in the anode 2 can be detected. A notch filter 5 is inserted in series between each anode 2 and the pipeline 1. The filter 5 provides a high impedance which can be signalled across but does not interfere with the cathodic protection system.

Abstract: An anode monitoring system for monitoring the integrity of anodes 2 provided on a metallic structure such as a pipeline system 1. A signal circuit Sn including the pipeline 1 and one of the anodes 2 is set up and appropriate signals are looked for at a central station 4. Reception of the signal at the central station 4 is dependent on the integrity of the anode 2 under inspection at that time. If the anode 2 is missing or defective the expected signal is not received and thus the fault in the anode 2 can be detected. A notch filter 5 is inserted in series between each anode 2 and the pipeline 1. The filter 5 provides a high impedance which can be signalled across but does not interfere with the cathodic protection system.

Abstract: An anode monitoring system for monitoring the integrity of anodes 2 provided on a metallic structure such as a pipeline system 1. A signal circuit Sn including the pipeline 1 and one of the anodes 2 is set up and appropriate signals are looked for at a central station 4. Reception of the signal at the central station 4 is dependent on the integrity of the anode 2 under inspection at that time. If the anode 2 is missing or defective the expected signal is not received and thus the fault in the anode 2 can be detected. A notch filter 5 is inserted in series between each anode 2 and the pipeline 1. The filter 5 provides a high impedance which can be signalled across but does not interfere with the cathodic protection system.

Abstract: Coupling apparatus for allowing transmission of electrical signals between a flowline (1) and a communications unit (4). The coupling apparatus comprises first (5) and second (8) portions of magnetic material. The first portion is arranged to receive the second portion and at least partially defines a flowline receiving aperture. The first and second portions (5,8) together form a magnetic circuit around the aperture and the second portion carries a winding (9) arranged for electrical connection to the communications unit (4). The winding links with the magnetic circuit when the second portion (8) is received in the first (5) such that an alternating current in the winding will generate a corresponding current in a flowline disposed in the aperture and vice versa. The arrangement allows the first portion to be permanently mounted on a flowline and the second portion to be inserted in situ.

Abstract: A subsurface object location apparatus for determining the position of an object 2 located below a surface S such as a land surface, the surface of the sea or a seabed. A subsurface unit 1 having transmitter means for transmitting inductive signals is mounted on the object 2. A plurality of surface units 3 are disposed at spaced locations at the surface S. Each surface unit 3 has receiver means arranged for receiving the inductive signals. Processing means 4 are provided for determining the location of the object 2 using time difference of arrival techniques in respect of the signals received at the surface units. Cyclic correlation is used in determining the times of reception of signals at the surface units.

Abstract: A data transmission system for use in extracting data from a downhole location in a well is disclosed. The well has electrically conductive downhole structure (2,C) which together with an earth return forms a signal circuit which is used to transmit data. A current source (34) is provided at the wellhead for applying a reference signal to the downhole structure (2,C). Effective impedance varying means (48) are located downhole and used for varying the effective impedance of the signal circuit in dependence on data to be transmitted to the wellhead. Monitoring means (35) for monitoring changes in the reference signal caused by varying the effective impedance of the signal circuit are located at the wellhead. Monitoring these changes allows data to be extracted. A separate reference earthing point may be provided for the monitoring means to alleviate the effect of imperfections in the earth connection (S) used to complete the signal circuit.

Abstract: Data transmission in pipeline systems A first set of apparatus is arranged for transmitting data from a point in a cased section of a well 1, 3 to a remote location. The apparatus may be used as a relay station 6 to increase operational depth. Signals are applied to and received from the string 1 at the relay station 6 and a selected length of the string 1 is provided with insulating spacer means 9 on either side of the relay station to ensure that the string 1 and casing 3 are effectively isolated for a selected minimum distance. This enables potential differences to be both applied to and detected from the string 1, thus allowing data transmission and reception. A second set of apparatus is arranged for transmitting from an internal unit 408 inside a cased section of the well 401, 403 to the immediate surrounding area outside the casing 403. The internal unit 408 injects current into the string 401. A toroid 415 which surrounds the casing 403 is provided to pick up signals.