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.

An electrode includes a structure comprising a porous material and an electrically-conductive liquid covering at least a portion of the porous material, wherein the electrode is configured to be immersed in fluids of interest, the electrically-conductive liquid being immiscible in the fluids of interest.

The disclosure relates to a method for monitoring the performances of a cable for carrying a downhole assembly in a wellbore, the cable comprising at least a conductive core and an insulating outer layer, comprising: measuring a downlink telemetry signal, transmitted from a surface control module to the downhole assembly, and/or an uplink telemetry signal, transmitted from the downhole assembly to the surface control module; representing the downlink and/or uplink telemetry signals as a function of a parameter representative of a depth of the downhole assembly, analyzing a variation of the telemetry signal as a function of the parameter in view of an electrical model of an installation including the cable and the downhole assembly disposed in the wellbore, determining location of anomalies of the cable based on the analysis.

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.

A well telemetry system supplies power to downhole sensor nodes employed for obtaining telemetry data in oil wells. The nodes are held in the cement that lines the well and surround the casing. At the surface, an AC power unit is connected to the casing and geological structure that surrounds the cement. Power to nodes is supplied using an AC resonant circuit that generates standing waves of electrical power on the casing. Power from the standing waves is delivered to the nodes which are located at antinodes of the standing wave. The nodes are held in cement that surround the casing, with one of their two electrodes connected to the casing and the other connected to the cement or to geological structure.

Systems and methods are presented for reducing electrical interference in measurement-while-drilling (MWD) data. An example may include, among other features a MWD data acquisition system including an analog data reception for receiving analog MWD data, an analog-to-digital conversion circuit, at least one isolation circuit for electrically isolating the analog data reception circuit and the analog-to-digital conversion circuit from a digital data transmission circuit. In some implementations, the data reception device may be at least partially powered by the battery.

The present invention relates to a method of installing an electrical earthing system, comprising: determining a borehole site, providing a drill string comprised of a conductive material and having a drill bit at an end thereof, and electrically connecting the drill string to an earth test terminal of a resistance testing apparatus, electrically connecting a test electrode or electrodes to a remaining terminal or terminals of the resistance testing apparatus and placing the test electrode(s) around the borehole, drilling the borehole using the drill string, periodically or continuously measuring and recording a total electrical resistance using the resistance testing apparatus, and adjusting the drill string to reduce the total electrical resistance towards a target total electrical resistance, removing the drill rod from the borehole and disconnecting the drill string from the resistance testing apparatus, installing an earthing electrode within the borehole, and backfilling the borehole with backfill ground material.

The present invention relates to a method of installing an electrical earthing system, comprising: determining a borehole site, providing a drill string comprised of a conductive material and having a drill bit at an end thereof, and electrically connecting the drill string to an earth test terminal of a resistance testing apparatus, electrically connecting a test electrode or electrodes to a remaining terminal or terminals of the resistance testing apparatus and placing the test electrode(s) around the borehole, drilling the borehole using the drill string, periodically or continuously measuring and recording a total electrical resistance using the resistance testing apparatus, and adjusting the drill string to reduce the total electrical resistance towards a target total electrical resistance, removing the drill rod from the borehole and disconnecting the drill string from the resistance testing apparatus, installing an earthing electrode within the borehole, and backfilling the borehole with backfill ground material.

A drill string communication system is described. An uphole transceiver can couple a signal onto the drill string at a power that is always greater that a selectable power for a downhole signal. Communication from a drill rig to an inground tool can be re-initiated using a maximum uphole transmit power of an uphole transceiver. A procedure can establish a new set of transmission parameters for a drill string signal to establish communication between the drill rig and the inground tool. The system can include a walkover locator that receives an active/inactive status-controlled electromagnetic locating signal. Responsive to a locating signal degradation, a reconfiguration command can modify the locating signal. The uphole transceiver and a downhole transceiver can automatically modify at least one parameter of a downhole signal. An uphole receiver can apply a compensation response to a transferred signal to compensate for a drill string channel transfer function.

A well system with an electrical control and sensing system includes a first conductor and a second conductor. A first switching circuit is coupled between the first conductor and the second conductor. The first switching circuit includes a first electrically powered device and a first diode coupled to the first electrically powered device. A sensor circuit is coupled between the first conductor and the second conductor. The sensor circuit includes a sensor and a sensor diode coupled to the sensor and configured to permit current flow through the sensor circuit from the second conductor to the first conductor.