A logging tool and a method for in-situ, independent calibration of receiver amplifier electronics separately from transmitter electronics. A logging tool can perform in-situ gain and phase calibration on one or more receiver assemblies, each consisting of at least a receiver amplifier electronics and a receiver antenna, and based on a calculated gain and phase of the receiver assembly, determine the true antenna amplitude and phase associated with a measurement made by the receiver assembly. The logging tool can perform in-situ crosstalk measurement and calibration, by determining a crosstalk matrix for all of the receiver assemblies and for each receiver assembly, removing the crosstalk interference from the measurement made by the receiver assembly.

A logging tool and a method for in-situ, independent calibration of receiver amplifier electronics separately from transmitter electronics. A logging tool can perform in-situ gain and phase calibration on one or more receiver assemblies, each consisting of at least a receiver amplifier electronics and a receiver antenna, and based on a calculated gain and phase of the receiver assembly, determine the true antenna amplitude and phase associated with a measurement made by the receiver assembly. The logging tool can perform in-situ crosstalk measurement and calibration, by determining a crosstalk matrix for all of the receiver assemblies and for each receiver assembly, removing the crosstalk interference from the measurement made by the receiver assembly.

A monitoring well installation comprising metallic casing (2) and a sealing material plug (6) provided downhole in the borehole for sealing the borehole against the egress of fluid from a zone below the plug. There is an uncased length of borehole at least 10 m in length in which the plug seals against the formation. There is provided a downhole sensing tool (3) located below the plug (6) and a communication arrangement (31, 5, 4) for use in transmitting data from the sensing tool towards the surface, which comprises an across plug communication apparatus (5) comprising a pair of spaced contacts (51) contacting the casing and/or the formation and a transmitter located below the plug (6) for transmitting signals carrying data across the plug towards the surface.

A monitoring well installation comprising metallic casing (2) and a sealing material plug (6) provided downhole in the borehole for sealing the borehole against the egress of fluid from a zone below the plug. There is an uncased length of borehole at least 10 m in length in which the plug seals against the formation. There is provided a downhole sensing tool (3) located below the plug (6) and a communication arrangement (31, 5, 4) for use in transmitting data from the sensing tool towards the surface, which comprises an across plug communication apparatus (5) comprising a pair of spaced contacts (51) contacting the casing and/or the formation and a transmitter located below the plug (6) for transmitting signals carrying data across the plug towards the surface.

Systems, methods, and devices for performing real-time detecting and spatially-positioning a waterfront in an oil-producing reservoirs are disclosed. An example method of predicting movement of a waterfront in a reservoir may include generating a plurality of electrical signals having different frequencies with a surface electric source; injecting currents corresponding to the plurality of generated signals into the earth near a well extending into the reservoir with a surface dipole; sensing a vertical component of an electric field generated by each of the injected currents at a location in the reservoir with a sensor; detecting a location of the waterfront within the reservoir based on the received vertical components of the electric fields; and analyzing the detected vertical components of the electric fields taken on at least two different points in time with machine learning to predict a rate of movement of the waterfront within the reservoir.

A transmitter is powered by a regulated battery voltage and is installable in one of a plurality of different housings, each housing is characterized by a different design and each can form part of an inground tool for performing an inground operation in which a drill string extends from a drill rig to the inground tool. An antenna driver drives an antenna based on the regulated voltage to emanate an electromagnetic signal for remote reception. A controller limits power consumption from the regulated voltage so as not to exceed a power consumption threshold, irrespective of installation of the transmitter in any one of the housings when the transmitter would otherwise exhibit a different power consumption for each housing design. A corresponding method is described. Features relating to power consumption threshold modification based on temperature as well as mechanical shock and vibration are described.

A transmitter is powered by a regulated battery voltage and is installable in one of a plurality of different housings, each housing is characterized by a different design and each can form part of an inground tool for performing an inground operation in which a drill string extends from a drill rig to the inground tool. An antenna driver drives an antenna based on the regulated voltage to emanate an electromagnetic signal for remote reception. A controller limits power consumption from the regulated voltage so as not to exceed a power consumption threshold, irrespective of installation of the transmitter in any one of the housings when the transmitter would otherwise exhibit a different power consumption for each housing design. A corresponding method is described. Features relating to power consumption threshold modification based on temperature as well as mechanical shock and vibration are described.

A monitoring well installation comprising metallic casing (2) and a sealing material plug (6) provided downhole in the borehole for sealing the borehole against the egress of fluid from a zone below the plug. There is an uncased length of borehole at least 10 m in length in which the plug seals against the formation. There is provided a downhole sensing tool (3) located below the plug (6) and a communication arrangement (31, 5, 4) for use in transmitting data from the sensing tool towards the surface, which comprises an across plug communication apparatus (5) comprising a pair of spaced contacts (51) contacting the casing and/or the formation and a transmitter located below the plug (6) for transmitting signals carrying data across the plug towards the surface.

A monitoring well installation comprising metallic casing (2) and a sealing material plug (6) provided downhole in the borehole for sealing the borehole against the egress of fluid from a zone below the plug. There is an uncased length of borehole at least 10 m in length in which the plug seals against the formation. There is provided a downhole sensing tool (3) located below the plug (6) and a communication arrangement (31, 5, 4) for use in transmitting data from the sensing tool towards the surface, which comprises an across plug communication apparatus (5) comprising a pair of spaced contacts (51) contacting the casing and/or the formation and a transmitter located below the plug (6) for transmitting signals carrying data across the plug towards the surface.

An illustrative permanent electromagnetic (EM) monitoring system including a casing string positioned inside a borehole penetrating a formation, a source electrode attached to the casing string, an electrically insulating layer on an outer surface of the source electrode that provides a capacitive coupling of the source electrode to the formation, a power supply coupled to the source electrode which injects electrical current into the formation via the capacitive coupling, and a processing unit that determines a formation property based on at least the current received by a return electrode.