Abstract: A through-casing formation monitoring system may include a casing string positioned within a wellbore, a power source electrically coupled to a first transmitter configured to produce a magnetic field, a magnetic induction sensor positioned within the casing string such that the magnetic induction sensor allows a continued operation of the wellbore, a fiber optic cable coupled to an electro-optical transducer within the magnetic induction sensor, and an optical interrogation system configured to receive measurements from the magnetic induction sensor via the fiber optic cable.

Abstract: A system includes a drillstring with an electromagnetic (EM) transmitter in a first borehole. The system also includes at least one fiber optic sensor deployed in a second borehole. The system also includes a processor configured to demodulate a data stream emitted by the EM transmitter based on EM field measurements collected by the at least one fiber optic sensor.

Abstract: A through-casing formation monitoring system may include a casing string positioned within a wellbore, a power source electrically coupled to the casing string, a voltage sensor electrically coupled to an inner surface of the casing string such that the voltage sensor allows a continued operation of the wellbore, a fiber optic cable coupled to an electro-optical transducer within the voltage sensor, and an optical interrogation system configured to measure an electric potential applied to the electro-optical transducer via the fiber optic cable.

Abstract: An example method for modeling a geological formation includes receiving a set of measurements from an electromagnetic logging tool and representing at least one characteristic of the geological formation as at least one continuous spatial function. At least one coefficient of the at least one continuous spatial function may be determined based, at least in part, on the set of measurements. At least one characteristic of the geological formation may be determined based, at least in part, on the at least one continuous spatial function.

Abstract: An antenna assembly includes a tool mandrel having a tool axis, and a coil including a plurality of windings wrapped about the tool mandrel at a winding angle offset from the tool axis. A soft magnetic band radially interposes the coil and the tool mandrel and extends about a circumference of the tool mandrel at a band angle orthogonal to the winding angle. The soft magnetic band includes a plurality of inserts, and a gap is defined between each laterally adjacent insert and the gap extends parallel to the tool axis.

Abstract: A communication system for use in a wellbore can include a first cylindrically shaped band that can be positioned around a first outer housing of a first subsystem of a well tool. The first cylindrically shaped band can be operable to electromagnetically couple with a second cylindrically shaped band. The second cylindrically shaped band can be positioned around a second outer housing of a second subsystem of the well tool. The first cylindrically shaped band can electromagnetically couple with the second cylindrically shaped band via an electromagnetic field or by transmitting a current to the second cylindrically shaped band through a fluid in the wellbore.

Abstract: An example logging tool may include at least one transmitter antenna and at least one receiver antenna. A first high-impedance metamaterial may be disposed between the transmitter antenna and the receiver antenna. The first high-impedance metamaterial may include a periodic arrangement of patches, each of the patches being electrically coupled to a ground plane using a via.

Abstract: An antenna assembly includes a tool mandrel having a tool axis, and a plurality of coils are collocated about the tool mandrel and each include a plurality of windings wrapped about the tool mandrel. A soft magnetic band radially interposes the plurality of coils and the tool mandrel and includes a plurality of inserts that form two or more annular arrays axially spaced from each other and extend about the tool mandrel at an angle orthogonal to the tool axis. The inserts in each annular array are circumferentially spaced from each other.

Abstract: A method includes introducing a resistivity logging tool including one or more transmitter coils and one or more receiver coils into a wellbore. First and second signals are then transmitted with a first transmitter coil at first and second frequencies, respectively, and a first receiver coil receives first and second response signals based on the first and second signals. A ratio between the first and second response signals is then calculated to obtain a ratio signal, and the ratio signal is processed in an inversion algorithm. One or more formation characteristics of the subterranean formation may then be determined based on the ratio signal as processed by the inversion algorithm.

Abstract: Permanent electromagnetic (EM) monitoring of the regions around and between wells may employ a casing string positioned within a borehole through the subsurface formations of interest. At least two passivated electrodes are mounted on the casing string to sense electric fields in the formation. Though only capacitively coupled to the formation, the passivated electrodes nevertheless provide a potential difference to an electro-optical transducer, which in turn modifies a property of the light passing along an optical fiber attached to the casing string. An interface unit senses the modified property to derive a measure of the electric field between each pair of passivated electrodes. The passivated electrodes have a contact surface that is conductive but for one or more layers of non-reactive (and thus electrically insulating) materials. Illustrative materials include metal oxides, polymers and ceramics, but the layers are preferably kept very thin to maximize the coupling capacitance with the formation.

Abstract: 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.

Abstract: Systems and methods are provided for using opto-electrical networks to control downhole electronic devices. A system is provided that can include an optical transmitter. The optical transmitter can generate a first electrical signal associated with a radio frequency or a frequency bandwidth of the radio frequency. The optical transmitter can also convert the first electrical signal to an optical signal. The optical transmitter can further transmit the optical signal over a fiber-optic cable to an optical receiver deployed in a wellbore. The system can include the optical receiver. The optical receiver can convert the optical signal to a second electrical signal associated with the radio frequency or the frequency bandwidth. The optical receiver can also control an electronic device in the wellbore that is identified from the radio frequency or the frequency bandwidth of the second electrical signal.

Abstract: Permanent electromagnetic (EM) monitoring of the regions around and between wells may employ a casing string positioned within a borehole through the subsurface formations of interest. At least two passivated electrodes are mounted on the casing string to sense electric fields in the formation. Though only capacitively coupled to the formation, the passivated electrodes nevertheless provide a potential difference to an electro-optical transducer, which in turn modifies a property of the light passing along an optical fiber attached to the casing string. An interface unit senses the modified property to derive a measure of the electric field between each pair of passivated electrodes. The passivated electrodes have a contact surface that is conductive but for one or more layers of non-reactive (and thus electrically insulating) materials. Illustrative materials include metal oxides, polymers and ceramics, but the layers are preferably kept very thin to maximize the coupling capacitance with the formation.