Abstract: Certain aspects of the present disclosure relate to precise position determination for the downhole placement and position of the tubing-side portion of a behind-casing measurement system. The position determination can be used to establish precise alignment of the system and thus prevent signal loss. A system according to some aspects includes a casing-side antenna mountable between a well casing and a formation wall and a processing device connected to the casing-side antenna. The processing device is operable to measure signal intensities for a signal received from at least one tubing-side antenna, calculate a position of the tubing-side antenna relative to the casing-side antenna based on the signal intensities, and transmit the position to the surface.

Abstract: Detecting discontinuities in a well casing according to some aspects includes actively monitoring the electric current response in an antenna or in antennas during the insertion of a tubing string. The method does not require permanent magnets, or any hardware elements beyond those that are already present in a typical behind-casing measurement system. A system according to some aspects includes an antenna that is mounted in or on a tubing string and a voltage source that can be connected to the antenna. A processing device is connected to the antenna and the voltage source. The processing device applies an AC voltage to the antenna and monitors a current generated in the antenna while the AC voltage is being applied.

Abstract: A downhole network-interface unit provides remote diagnostics and control for a downhole communications network. A network-interface unit may convert native format signals from downhole devices to a signal to be sent to a surface controller. Remote diagnostics of signal anomalies in the downhole network can be provided by the network-interface unit to provide diagnostics information, such as measurements or signal waveforms, to the surface. In some examples, the network-interface unit can also segment the downhole network as needed to maintain network health and integrity. Network segmentation can take place automatically in response to determining an anomalous condition or can be directed from a surface controller.

Abstract: A downhole networking interface unit provides conversion between multiple native format signals of downhole instruments to power line communication messages exchanged with a controller positionable at the surface of a wellbore. Certain aspects and features provide methods of power line communication. In one aspect, a computing device may send and receive messages in a power line communication format over a cable to and from at least one downhole device. The computing device may send and receive messages in the power line communication format to and from a network interface unit that can be coupled to the cable. The network interface unit may have multiple interfaces for communicating downhole using differing types of native signals for differing types of downhole devices such as sensor, instruments, and inductive couplers.

Abstract: A tubing string can be at a first position in a wellbore and can move to a second position in the wellbore with respect to a casing string. The tubing string can include a first tubing-side antenna and a second tubing-side antenna coupled at different locations on the tubing string. The first tubing-side antenna can communicatively couple to a casing-side antenna when the tubing string is at the first position in the wellbore, and can be out of communication range with the casing-side antenna when the tubing string is at the second position. The second tubing-side antenna can be coupled at a second location that is spaced a distance from the first location on the tubing string such that the second tubing-side antenna communicatively couples to the casing-side antenna when the tubing string is at the second position.

Abstract: Detecting discontinuities in a well casing according to some aspects includes actively monitoring the electric current response in an antenna or in antennas during the insertion of a tubing string. The method does not require permanent magnets, or any hardware elements beyond those that are already present in a typical behind-casing measurement system. A system according to some aspects includes an antenna that is mounted in or on a tubing string and a voltage source that can be connected to the antenna. A processing device is connected to the antenna and the voltage source. The processing device applies an AC voltage to the antenna and monitors a current generated in the antenna while the AC voltage is being applied.

Abstract: Certain aspects of the present disclosure relate to precise position determination for the downhole placement and position of the tubing-side portion of a behind-casing measurement system. The position determination can be used to establish precise alignment of the system and thus prevent signal loss. A system according to some aspects includes a casing-side antenna mountable between a well casing and a formation wall and a processing device connected to the casing-side antenna. The processing device is operable to measure signal intensities for a signal received from at least one tubing-side antenna, calculate a position of the tubing-side antenna relative to the casing-side antenna based on the signal intensities, and transmit the position to the surface.

Abstract: A downhole networking interface unit provides conversion between multiple native format signals of downhole instruments to power line communication messages exchanged with a controller positionable at the surface of a wellbore. Certain aspects and features provide methods of power line communication. In one aspect, a computing device may send and receive messages in a power line communication format over a cable to and from at least one downhole device. The computing device may send and receive messages in the power line communication format to and from a network interface unit that can be coupled to the cable. The network interface unit may have multiple interfaces for communicating downhole using differing types of native signals for differing types of downhole devices such as sensor, instruments, and inductive couplers.

Abstract: A downhole network-interface unit provides remote diagnostics and control for a downhole communications network. A network-interface unit may convert native format signals from downhole devices to a signal to be sent to a surface controller. Remote diagnostics of signal anomalies in the downhole network can be provided by the network-interface unit to provide diagnostics information, such as measurements or signal waveforms, to the surface. In some examples, the network-interface unit can also segment the downhole network as needed to maintain network health and integrity. Network segmentation can take place automatically in response to determining an anomalous condition or can be directed from a surface controller.

Abstract: An antenna system can include casing-side antennas and a full wave rectifier. The casing-side antennas can be coupled to a casing string that is positioned in a wellbore for communicatively coupling to a tubing-side antenna positioned in the wellbore. Each of the casing-side antennas can include a conductive wire positioned to carry current that can be induced on the conductive wire in response to an electromagnetic field from the tubing-side antenna. A direction, relative to a common antenna junction point, of the current on the conductive wire can be opposite to the direction, relative to the common antenna junction point, in which an adjacent casing-side antenna is positioned to carry current induced in response to the electromagnetic field. The full-wave rectifier can be conductively coupled to the casing-side antennas for converting alternating current that can be generated on the casing-side antennas into direct current.

Abstract: A shunt current regulator can be used to maintain current levels at downhole device on a tubing encapsulated cable and improve communication speed between the surface and downhole devices. The shunt current regulator reduces the current noise on the tubing encapsulated cable allowing for higher bitrate transfer. In some aspects, a sensing element monitors the current drawn and generates a sense signal. In other aspects, a compensation signal is generated from the sense signal. The compensation signal may be used as input to control a transistor to regulate the current drawn from the tubing encapsulated cable. The transistor can dissipate power to stabilize the current drawn or provide compensation current to increase the current drawn.

Abstract: A tubing string can be at a first position in a wellbore and can move to a second position in the wellbore with respect to a casing string. The tubing string can include a first tubing-side antenna and a second tubing-side antenna coupled at different locations on the tubing string. The first tubing-side antenna can communicatively couple to a casing-side antenna when the tubing string is at the first position in the wellbore, and can be out of communication range with the casing-side antenna when the tubing string is at the second position. The second tubing-side antenna can be coupled at a second location that is spaced a distance from the first location on the tubing string such that the second tubing-side antenna communicatively couples to the casing-side antenna when the tubing string is at the second position.

Abstract: An antenna system can include casing-side antennas and a full wave rectifier. The casing-side antennas can be coupled to a casing string that is positioned in a wellbore for communicatively coupling to a tubing-side antenna positioned in the wellbore. Each of the casing-side antennas can include a conductive wire positioned to carry current that can be induced on the conductive wire in response to an electromagnetic field from the tubing-side antenna. A direction, relative to a common antenna junction point, of the current on the conductive wire can be opposite to the direction, relative to the common antenna junction point, in which an adjacent casing-side antenna is positioned to carry current induced in response to the electromagnetic field. The full-wave rectifier can be conductively coupled to the casing-side antennas for converting alternating current that can be generated on the casing-side antennas into direct current.

Abstract: An electric system for measurement and control in an oil/gas well using transmission of electric signals and supply of electric power. The system is provided with a current loop having an essentially constant current in a current loop and a number of downhole network nodes (1N) which are connected to the system.

Abstract: An electric system especially for measurement and control in an oil/gas well using transmission of electric signals and supply of electric power. The system is provided with a current loop (5,6) having an essentially constant current in a current loop and a number of downhole network nodes (1N) which are connected to the system.