Abstract: Downhole electrical energy harvesting and communication in systems for well installations having metallic structure carrying electric current, for example CP current. In some instances there is a harvesting module (4) electrically connected to the metallic structure (2) at a first location and to a second location spaced from the first location, the first and second locations being chosen such that, in use, there is a potential difference therebetween due to the electric current flowing in the structure (2); and the harvesting module (4) being arranged to harvest electrical energy from the electric current. In addition or alternatively, there may be communication apparatus (4, 5, 6) for communication by modulation of the current, for example CP current, in the metallic structure (2).

Abstract: Downhole electrical energy harvesting and communication in systems for well installations having metallic structure carrying electric current, for example CP current. In some instances there is a harvesting module (4) electrically connected to the metallic structure (2) at a first location and to a second location spaced from the first location, the first and second locations being chosen such that, in use, there is a potential difference therebetween due to the electric current flowing in the structure (2); and the harvesting module (4) being arranged to harvest electrical energy from the electric current. In addition or alternatively, there may be communication apparatus (4, 5, 6) for communication by modulation of the current, for example CP current, in the metallic structure (2).

Abstract: Downhole electrical energy harvesting and communication in systems for well installations having metallic structure carrying electric current, for example CP current. In some instances there is a harvesting module (4) electrically connected to the metallic structure (2) at a first location and to a second location spaced from the first location, the first and second locations being chosen such that, in use, there is a potential difference therebetween due to the electric current flowing in the structure (2); and the harvesting module (4) being arranged to harvest electrical energy from the electric current. In addition or alternatively, there may be communication apparatus (4, 5, 6) for communication by modulation of the current, for example CP current, in the metallic structure (2).

Abstract: A lateral bore communication system where data signals are transmitted across the break in conductive path between a main bore and a lateral bore using a downhole structure section which has an electrode provided around a tubing portion and separated therefrom by an insulating layer.

Abstract: An electrical power and/or electrical signal transmission system for transmitting electrical power and/or electrical signals from a location on a first side of a metallic wall to a location on a second side of the metallic wall includes a transmitting apparatus having an electrical source and a first transformer. A receiving apparatus has a receiving module for receiving electrical power and/or electrical signals and a second transformer. First and second ends of a primary winding of the second transformer are electrically connected to respective spaced locations on the second, opposite, side of the metallic wall for picking up electrical power and/or electrical signals from the metallic wall. The receiving module is electrically connected to a secondary winding of the second transformer to enable electrical power and/or electrical signals to be transmitted from the electrical source to the receiving module.

Abstract: Downhole electrical power generation apparatus and methods of using stored pressurized gas and/or ambient downhole pressure. One example comprises first and second fluid receiving chambers, a fluid communication path for allowing flow of fluid from the first chamber via the fluid communication path to the second chamber and a turbine generator disposed so that fluid flowing from the first chamber via the fluid communications path to the second chamber operates the turbine generator to generate electrical power.

Abstract: An impressed current cathodic protection arrangement includes an elongate metallic structure to be protected and cathodic protection apparatus which comprises a DC power supply and an anode. One terminal of the power supply is connected to the structure at a connection point and another terminal of the power supply is connected to the anode. The arrangement includes monitoring apparatus for monitoring effectiveness of cathodic protection provided by the cathodic protection apparatus by determining the electrical potential of the structure relative to surroundings at at least one location which is spaced from the connection point.

Abstract: Downhole water level detecting apparatus for detecting the level of water in a formation in the region of a well installation. The detecting apparatus includes a transmitter for applying electrical signals to a signaling loop at a first location. The signaling loop includes a downhole metallic structure of the well installation and an earth return. The detecting apparatus also includes a detector for monitoring electrical signals in the signaling loop, and an evaluation unit arranged for determining a level of water in the formation relative to the downhole metallic structure in dependence on the monitored signals.

Abstract: Downhole water level detecting apparatus for detecting the level of water in a formation in the region of a well installation. The detecting apparatus includes a transmitter for applying electrical signals to a signaling loop at a first location. The signaling loop includes a downhole metallic structure of the well installation and an earth return. The detecting apparatus also includes a detector for monitoring electrical signals in the signaling loop, and an evaluation unit arranged for determining a level of water in the formation relative to the downhole metallic structure in dependence on the monitored signals.

Abstract: A well installation communication system includes downhole metallic structure 2, a downhole communication unit 3, and a surface communication unit 4 arranged for electrical signal communication with the downhole communication unit via a signal channel. The signal channel includes a portion of the downhole metallic structure 2, a portion of cable 5 running within the downhole metallic structure away from said portion of the downhole metallic structure towards the surface and a connection device 6. The connection device 6 is in the signal channel between the portion of metallic structure 2 and the portion of cable 5. The connection device is removeably deployed in the metallic structure, is electrically disconnectably and reconnectably connected to the metallic structure and has a connector portion to which an end of the cable is mechanically and electrically connected.

Abstract: A well installation includes a 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: 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: A lateral bore communication system where data signals are transmitted across the break in conductive path between a main bore and a lateral bore using a downhole structure section which has an electrode provided around a tubing portion and separated therefrom by an insulating layer.

Abstract: An impressed current cathodic protection arrangement includes an elongate metallic structure to be protected and cathodic protection apparatus which comprises a DC power supply and an anode. One terminal of the power supply is connected to the structure at a connection point and another terminal of the power supply is connected to the anode. The arrangement includes monitoring apparatus for monitoring effectiveness of cathodic protection provided by the cathodic protection apparatus by determining the electrical potential of the structure relative to surroundings at at least one location which is spaced from the connection point.

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: Downhole water level detecting apparatus for detecting the level of water in a formation in the region of a well installation. The detecting apparatus includes a transmitter for applying electrical signals to a signaling loop at a first location. The signaling loop includes a downhole metallic structure of the well installation and an earth return. The detecting apparatus also includes a detector for monitoring electrical signals in the signaling loop, and an evaluation unit arranged for determining a level of water in the formation relative to the downhole metallic structure in dependence on the monitored signals.

Abstract: An electrical power and/or electrical signal transmission system for transmitting electrical power and/or electrical signals from a location on a first side of a metallic wall to a location on a second side of the metallic wall includes a transmitting apparatus having an electrical source and a first transformer. A receiving apparatus has a receiving module for receiving electrical power and/or electrical signals and a second transformer. First and second ends of a primary winding of the second transformer are electrically connected to respective spaced locations on the second, opposite, side of the metallic wall for picking up electrical power and/or electrical signals from the metallic wall. The receiving module is electrically connected to a secondary winding of the second transformer to enable electrical power and/or electrical signals to be transmitted from the electrical source to the receiving module.

Abstract: A downhole signal receiving system where a pair of setting devices (51) are used to electrically connect with downhole structure and are connected to one another by a bulk conductor (52). Signals are extracted by using a detecting means (53) that does not interrupt the conduction path. The tool provides a low impedance conduction path along which signals from the surrounding structure can flow to facilitate detection.

Abstract: A flowline electrical impedance generation apparatus for generating a local electrical impedance in a metallic tubing portion of a flowline may be used in place of insulation joints in various systems. The impedance generation apparatus is tuned or tuneable to achieve maximum impedance at chosen frequencies, i.e., frequencies which it is desired to block.

Abstract: Downhole electrical power generation apparatus and methods of using stored pressurized gas and/or ambient downhole pressure. One example comprises first and second fluid receiving chambers, a fluid communication path for allowing flow of fluid from the first chamber via the fluid communication path to the second chamber and a turbine generator disposed so that fluid flowing from the first chamber via the fluid communications path to the second chamber operates the turbine generator to generate electrical power.