Abstract: A system for performing downhole logging operations includes a conductor coil configured to alternate between producing a magnetic field and measuring a magnetic field induced in a formation, a power supply couplable to the conductor coil for providing an electrical control current to conductor coil, and a signal acquisition system couplable to the conductor coil. The system further includes a permanent magnet coupled to the conductor coil, and a multi-state switch operable in a first state and a second state. In the first state, the conductor coil is coupled to an output of the power supply and decoupled from an input of the signal acquisition system. In the second state, the conductor coil is coupled to the input of acquisition electronics and decoupled from the output of the power supply.

Abstract: Methods and apparatus for evaluating an earth formation for generating a numerical model comprising an expression equating a representation for the effective conductivity under Archie's law with respect to direct current with a function for the effective conductivity representative of the mixing model with respect to direct current; and solving a system of equations to obtain values for the Archie parameters including at least i) the expression; ii) a second expression equating a first order variation of the representation with a first order variation of the function with respect to water saturation of the formation (Sw); and iii) a third expression equating a first order variation of the representation with a first order variation of the function with respect to porosity of the formation (?). The second and third expressions may equate derivatives of the representation with derivatives of the function.

Abstract: A multi-frequency tuning circuit includes a first branch including a first inductor and a first capacitor arranged in series and a second branch including a second inductor and a second capacitor arranged in series. The circuit is arranged within a circuitry module configured to be positioned between a source and a load, the first branch and the second branch both associated with loads, from the source, having low impedance frequencies. In order to improve transmitter antenna output power for downhole tools, the tuning circuit creates high impedance at operating frequencies between frequencies corresponding to low impedance.

Abstract: Methods, systems, devices, and products for taking multi-component induction tool measurements of a three-dimensional space from an interior of a plurality of nested tubulars in a borehole in an earth formation and estimating the property for each of the at least two tubulars using the multi-component induction tool measurements. The multicomponent induction tool measurements may be responsive to a property corresponding to at least two conductive tubulars of the plurality of nested tubular. Taking multi-component induction tool measurements may include taking three-dimensional low-frequency sinusoidal frequency domain waveform resistivity measurements and taking three-dimensional transient EM measurements with the multi-component induction tool.

Abstract: A multi-frequency tuning circuit includes a first branch including a first inductor and a first capacitor arranged in series and a second branch including a second inductor and a second capacitor arranged in series. The circuit is arranged within a circuitry module configured to be positioned between a source and a load, the first branch and the second branch both associated with loads, from the source, having low impedance frequencies. In order to improve transmitter antenna output power for downhole tools, the tuning circuit creates high impedance at operating frequencies between frequencies corresponding to low impedance.

Abstract: Methods and apparatus for evaluating an earth formation intersected by a borehole. Methods include using at least one transmitter to generate electromagnetic (EM) waves propagating through the formation; generating measurement signals at at least one receiver responsive to the propagating EM waves; taking a plurality of propagation measurements from the measurement signals representative of the propagating EM waves, where each propagation measurement of the plurality comprises at least one of: i) a relative phase shift between a first wave of the plurality of propagating EM waves and a second wave of the plurality of propagating EM waves; and ii) a relative attenuation between a first wave of the plurality of propagating EM waves and a second wave of the plurality of propagating EM waves; and performing a single inversion which uses the plurality of propagation measurements as input and generates at least one petrophysical parameter as output.

Abstract: A system for performing downhole logging operations includes a conductor coil configured to alternate between producing a magnetic field and measuring a magnetic field induced in a formation, a power supply couplable to the conductor coil for providing an electrical control current to conductor coil, and a signal acquisition system couplable to the conductor coil. The system further includes a permanent magnet coupled to the conductor coil, and a multi-state switch operable in a first state and a second state. In the first state, the conductor coil is coupled to an output of the power supply and decoupled from an input of the signal acquisition system. In the second state, the conductor coil is coupled to the input of acquisition electronics and decoupled from the output of the power supply.

Abstract: A system for performing downhole logging operations includes a power supply for providing a current and a conductor coil electrically coupled to receive the current from the power supply. The system further includes a switch electrically coupled to the power supply for controlling current provided to the conductor coil and enabling a pulse of current to be supplied to the conductor coil for an “on” duration and turning off current provided to the conductor coil for an “off” duration after the “on” duration, in which the “off” duration lasts longer than the “on” duration. The system also includes a permanent magnet coupled to the conductor coil. The conductor coil receives the pulse of current from the power supply during the “on” duration and not receiving current during the “off” duration. The pulse of current causes the permanent magnet to reverse polarity and generate a transient magnetic field.

Abstract: Systems, devices, and methods for estimating a value of a downhole parameter of interest. Aspects include an apparatus for evaluating a tubular. The apparatus may include a sensor including an electromagnetic acoustic transducer (EMAT) device configured to be conveyed into the tubular. The EMAT device may include measurement circuitry comprising at least one conductive coil; and a magnet array comprising magnets arranged with a corresponding direction of magnetization of each magnet oriented according to a configuration producing a greater magnetic flux on a first side of the array than on a second side opposing the first side. The magnetic flux produced from the second side may be substantially zero. In embodiments, the configuration of magnets comprises at least a first set of permanent magnets in a linear Halbach configuration.

Abstract: Methods, systems, devices, and products for taking multi-component induction tool measurements of a three-dimensional space from an interior of a plurality of nested tubulars in a borehole in an earth formation and estimating the property for each of the at least two tubulars using the multi-component induction tool measurements. The multicomponent induction tool measurements may be responsive to a property corresponding to at least two conductive tubulars of the plurality of nested tubular. Taking multi-component induction tool measurements may include taking three-dimensional low-frequency sinusoidal frequency domain waveform resistivity measurements and taking three-dimensional transient EM measurements with the multi-component induction tool.

Abstract: A nuclear magnetic resonance apparatus for estimating properties of an earth formation includes a carrier configured to be deployed in a borehole in the earth formation and at least one transmitting assembly disposed in the carrier and configured to generate an oscillating magnetic field in a volume of interest within the earth formation. The apparatus also includes at least one receiving assembly disposed in the carrier and configured to detect a nuclear magnetic resonance (NMR) signal originating in the volume of interest. In this apparatus, the receiving assembly includes at least a first longitudinal region with a loop coil and a butterfly coil, the loop coil central axis being located over a region of the magnet assembly where a static magnetic field is predominantly along an azimuthal direction to the carrier and the butterfly coil being at least partially overlapped with the loop coil to reduce mutual coupling.

Abstract: Nuclear magnetic resonance apparatuses and methods for estimating properties of an earth formation are provided. An apparatus includes a carrier configured to be deployed in a borehole, at least one transmitting assembly configured to generate an oscillating magnetic field in a volume of interest within the earth formation, at least one receiving assembly configured to detect a nuclear magnetic resonance (NMR) signal originating in the volume of interest; and a magnet assembly configured to generate a static magnetic field in the formation from a primary side of the magnet assembly. The magnet assembly includes an array of longitudinally elongated magnets having a rotating pattern of magnetic orientations, the array configured to generate the static magnetic field in the volume of interest, and the static magnetic field strength is higher at the primary side than the field strength at a side of the magnet assembly that is opposite the primary side.

Abstract: Systems, methods, and devices for evaluation of an earth formation intersected by a borehole using a logging tool. Methods include exciting an upper and lower transmitter; receiving signals at a plurality of receivers between the upper and lower transmitter; estimating a phase shift attributable to a volume of interest of the formation adjacent to a section of the carrier corresponding to the plurality of receivers by estimating phase shifts attributable only to portions of the volume of interest adjacent to corresponding portions of the section between each adjacent pair of receivers of the plurality of receivers; wherein each adjacent pair is positioned at a corresponding distance that is no more than half of the shortest wavelength of those wavelengths associated with the received signals. Estimating a phase shift between an adjacent pair of receivers may be carried out using a first relative phase value; and a second relative phase value.

Abstract: Methods and apparatus for evaluating an earth formation intersected by a borehole. Methods include using at least one transmitter to generate electromagnetic (EM) waves propagating through the formation; generating measurement signals at at least one receiver responsive to the propagating EM waves; taking a plurality of propagation measurements from the measurement signals representative of the propagating EM waves, where each propagation measurement of the plurality comprises at least one of: i) a relative phase shift between a first wave of the plurality of propagating EM waves and a second wave of the plurality of propagating EM waves; and ii) a relative attenuation between a first wave of the plurality of propagating EM waves and a second wave of the plurality of propagating EM waves; and performing a single inversion which uses the plurality of propagation measurements as input and generates at least one petrophysical parameter as output.

Abstract: Systems, devices, and methods for estimating a value of a downhole parameter of interest. Aspects include an apparatus for evaluating a tubular. The apparatus may include a sensor including an electromagnetic acoustic transducer (EMAT) device configured to be conveyed into the tubular. The EMAT device may include measurement circuitry comprising at least one conductive coil; and a magnet array comprising magnets arranged with a corresponding direction of magnetization of each magnet oriented according to a configuration producing a greater magnetic flux on a first side of the array than on a second side opposing the first side. The magnetic flux produced from the second side may be substantially zero. In embodiments, the configuration of magnets comprises at least a first set of permanent magnets in a linear Halbach configuration.

Abstract: A method for inverting dielectric logging tool measurement data to estimate an electrical characteristic of an earth formation includes: receiving measurement data from the logging tool having a transmitter antenna and receiver antennas spaced known distances from the transmitter antenna; establishing an equation relating magnetic field measurements made by the receiver antennas to the distances and a wave vector; establishing an error equation that quantifies a difference between the magnetic field measurements made by the receiver antennas to magnetic field measurements made by the receiver antennas that would be obtained with an estimated formation electrical characteristic; calculating an error using the error equation for an initial estimated value of the wave vector that comprises a term having a first number multiplied times a second number of radians to provide a plurality of calculated errors; and determining a minimum error from the plurality of calculated errors to estimate the electrical character

Abstract: A nuclear magnetic resonance apparatus for estimating properties of an earth formation includes a carrier configured to be deployed in a borehole in the earth formation and at least one transmitting assembly disposed in the carrier and configured to generate an oscillating magnetic field in a volume of interest within the earth formation. The apparatus also includes at least one receiving assembly disposed in the carrier and configured to detect a nuclear magnetic resonance (NMR) signal originating in the volume of interest. In this apparatus, the receiving assembly includes at least a first longitudinal region with a loop coil and a butterfly coil, the loop coil central axis being located over a region of the magnet assembly where a static magnetic field is predominantly along an azimuthal direction to the carrier and the butterfly coil being at least partially overlapped with the loop coil to reduce mutual coupling.

Abstract: Methods and apparatus for evaluating an earth formation for generating a numerical model comprising an expression equating a representation for the effective conductivity under Archie's law with respect to direct current with a function for the effective conductivity representative of the mixing model with respect to direct current; and solving a system of equations to obtain values for the Archie parameters including at least i) the expression; ii) a second expression equating a first order variation of the representation with a first order variation of the function with respect to water saturation of the formation (Sw); and iii) a third expression equating a first order variation of the representation with a first order variation of the function with respect to porosity of the formation (?). The second and third expressions may equate derivatives of the representation with derivatives of the function.

Abstract: Systems, methods, and devices for evaluation of an earth formation intersected by a borehole using a logging tool. Methods include exciting an upper and lower transmitter; receiving signals at a plurality of receivers between the upper and lower transmitter; estimating a phase shift attributable to a volume of interest of the formation adjacent to a section of the carrier corresponding to the plurality of receivers by estimating phase shifts attributable only to portions of the volume of interest adjacent to corresponding portions of the section between each adjacent pair of receivers of the plurality of receivers; wherein each adjacent pair is positioned at a corresponding distance that is no more than half of the shortest wavelength of those wavelengths associated with the received signals. Estimating a phase shift between an adjacent pair of receivers may be carried out using a first relative phase value; and a second relative phase value.

Abstract: An apparatus for estimating a property of an earth formation includes: a carrier configured to be conveyed through a borehole penetrating an earth formation; a first fractal-shaped antenna element disposed on the carrier and configured to at least one of transmit electromagnetic energy into the formation and receive electromagnetic energy from the formation; and a second fractal-shaped antenna element electrically connected to the first fractal-shaped antenna element at a connection and configured to at least one of transmit electromagnetic energy into the formation and receive electromagnetic energy from the formation; wherein the second fractal-shaped antenna element is substantially a mirror image of the first fractal antenna element with respect to a reflection about the connection.