Abstract: An electromagnetic logging apparatus is disclosed which employs dielectric-filled slot antennas, in conjunction with tuning elements, to obtain improved operation. The apparatus can be used to measure the dielectric constant of formations surrounding a borehole.

Abstract: Apparatus for determining the dielectric constant and/or resistivity of earth formations traversed by a borehole includes a transmitter which transmits electromagnetic energy into the earth formation from a first location in the borehole at a frequency which enables the electromagnetic energy to propagate throughout the surrounding earth formations. Receivers receive electromagnetic energy at two locations in the borehole which are spaced longitudinally from the transmitter provide signals representative of the total electromagnetic fields at the receiver locations. Circuitry determines the dielectric constant and/or resistivity of the formations in accordance with a secondary field ratio and a phase difference derived from the signals provided by the receivers.

Abstract: Method and apparatus for use in introducing electromagnetic energy into subsurface earth formations and acquiring measurements relating to propagation of such energy therethrough. A logging tool body includes a plurality of transmitter and receiver antenna assemblies positionable against the borehole wall. Construction of each antenna assembly includes a cavity-backed slot resonated by lumped elements, the slots being oriented generally with their elongate dimension transverse to the tool body. The transmitters and receivers are interconnected, respectively, to a downhole source of electromagnetic energy operating nominally at 200 MHz and to appropriate receiver circuitry. Formation dielectric constants are determined from phase differences and relative amplitude ratios of energy from the formation incident on the receiver antennas.

Abstract: An electromagnetic logging apparatus is disclosed which employs dielectric-filled button antennas, in conjunction with tuning elements, to obtain improved operation. The apparatus can be used to measure the dielectric constant of formations surrounding a borehole.

Abstract: Well logging techniques are set forth for obtaining improved measurements of formation dielectric permittivity, conductivity, and water-filled porosity. The effects of dielectric and conductivity frequency dispersion are considered and utilized. In a disclosed embodiment, a corrected dielectric permittivity of a formation surrounding a borehole is determined using the following steps: deriving a measured value of formation dielectric permittivity from a logging device which traversed the borehole; deriving a measured value of formation conductivity from a logging device which traversed the borehole; determining a formation dielectric permittivity dispersion value as a function of the measured conductivity; and determining a corrected formation dielectric permittivity from the measured value of dielectric permittivity and the dispersion value.

Abstract: An improved very high frequency induction log is obtained using a tool having a focused transmitter source. The tool utilizes a second transmitter placed on the opposite side of the receivers from the first transmitter, the second transmitter being supplied with current to produce an opposite antenna current direction to the first transducer. The combination of the two transmitters serves to focus the current flow and increase the depth of investigation.

Abstract: A well logging system and method of the present invention determines the dielectric constant and/or conductivity of earth formations some of which have fluid invasion. The system and method of the present invention includes the transmission of electromagnetic energy into the earth formation from a first location in a borehole in the formations at a frequency which enables the electromagnetic energy to propagate throughout the surrounding earth formations. Electromagnetic energy is received by receivers at three locations in the borehole which are spaced longitudinally from the location of the transmission of the electromagnetic energy. The receivers provide signals representative of the total electromagnetic fields at those locations. The dielectric constant and/or resistivity of the earth formations are determined in accordance with portions of the signals from the three receivers corresponding to secondary electromagnetic fields at the three receiving locations.

Abstract: A dielectric well logging system is provided to determine dielectric constant and resistivity in formations invaded by water to determine oil and water saturations of the formations. Plural transmitters are activated in a time division multiplex manner and sensed by receiver coils. The amplitude ratio and phase difference between the signals sensed by the receiver coils are then used to determine dielectric constant and resistivity which may then be used to determine invasion characteristics.

Abstract: The disclosure is applicable to a borehole logging device of the type which includes an elongated body suspendable in a borehole and having at least one transmitting antenna and at least one receiving antenna mounted in spaced relation in the body. Energizing signals are applied to the transmitting antenna to produce electromagnetic energy, a portion of which is received at the receiving antenna after being affected by earth formations surrounding the borehole. In accordance with the disclosed invention, a region of the body is loaded with a dielectric material having a dielectric constant selected to minimize, at the receiving antenna, the effect of spurious transverse magnetic mode components of standing wave electromagnetic energy within the body.

Abstract: An improvement to a conventional one transmitter coil-two receiver coil dielectric well logging sonde permits the well logging sonde to have deeper penetration of the earthen formation when measuring dielectric constants. The improvement includes increased spacing between the receiver coils and the transmitter coil and operation of the transmitter coil at a higher power level.

Abstract: A well logging system and method of the present invention determines the dielectric constant and/or conductivity of earth formations some of which have fluid invasion. The system and method of the present invention include the transmission of electromagnetic energy into the earth formations from a first location in a borehole in the formations at a frequency which enables the electromagnetic energy to propagate throughout the surrounding earth formations. Electromagnetic energy is received by receivers at three locations in the borehole which are spaced longitudinally from the location of the transmission of the electromagnetic energy. The receivers provide signals representative of the received electromagnetic energy. The dielectric constant and/or resistivity of the earth formations are determined in accordance with the signals from the three receivers.

Abstract: An electromagnetic logging apparatus for investigating properties of an earth formation surrounding a borehole comprises an electromagnetic energy transmitter and four receivers supported by a support member, a measurement channel, and a multiplexer for selectively coupling the measurement channel to the receivers. The measurement channel comprises an amplitude processing channel including a highly gain-stabilized amplifier and gain control circuit; a phase processing channel including a highly phase-stabilized amplifier; and a circuit for measuring the amplitude and phase. The gain of the gain-stabilized amplifier is controlled by the gain control circuit in a closed loop feedback arrangement, while the gain of the phase-stabilized amplifier is controlled by the same gain control circuit without the closed loop arrangement.

Abstract: The disclosure is directed to an apparatus and method for subsurface electromagnetic logging in a borehole wherein means are provided to detect transverse magnetic mode components and to either correct for these spurious components in the processing of the received signals or to generate suitable cancelling signals.

Abstract: Transmitting and receiving coils for radio frequency (RF) dielectric well logging are shielded in copper enclosures to substantially remove unwanted electrostatic or capacitive signals introduced by the conductive fluids in the well bore.

Abstract: A method and apparatus for logging rock formations penetrated by a borehole to determine both the resistivity and dielectric constant of the formations. The apparatus comprises an induction logging tool having at least a transmitting coil and two receiver coils and operating in the radio frequency range from 20 to 60 megahertz. The method utilizes both the in-phase and out-of-phase, with respect to the transmitter current, voltage components which are measured at each receiver. The in-phase and out-of-phase voltage components are used to compute the phase shift between the voltage signals and the relative attenuation of the voltage amplitudes between the receivers. The phase shifts and relative attenuations are relatively insensitive to the borehole (e.g., borehole radius and drilling mud resistivity) and can be used as inputs into theoretically constructed nomograms to determine both the resistivity and dielectric constant of the formation.

Abstract: A dielectric well logging system has its coils aligned radially, rather than in alignment, with respect to the longitudinal axis of a sonde which moves the coils through a borehole. Improved shielding is also provided. The coils have different and improved response characteristics.

Abstract: A method and apparatus for logging rock formations penetrated by a borehole to determine both the resistivity and dielectric constant of the formations. The apparatus comprises an induction logging tool having at least a transmitting coil and two receiver coils and operating in the radio frequency range from 20 to 60 megahertz. The method utilizes both the in-phase and out-of-phase, with respect to the transmitter current, voltage components which are measured at each receiver. The in-phase and out-of-phase voltage components are used to compute the phase shift between the voltage signals and the relative attenuation of the voltage amplitudes between the receivers. The phase shifts and relative attenuations are relatively insensitive to the borehole (e.g., borehole radius and drilling mud resistivity) and can be used as inputs into theoretically constructed nomograms to determine both the resistivity and dielectric constant of the formation.