Methods, systems and devices for evaluating an earth formation, including an electromagnetic (EM) well logging apparatus for investigating a formation from a fluid-filled borehole intersecting the formation. Apparatus include a carrier body having a pocket formed in an outer surface, the pocket being defined by a plurality of walls and a bottom; a pad configured to emit EM energy, the pad having an outer face, a plurality of sides complementary to the plurality of walls, and an inner face positioned adjacent to the bottom, wherein the pad is movably disposed in the pocket such that a gap separates at least one wall of the plurality of walls and at least one side of the plurality of sides; and at least one electrically conductive member forming an electrical connection between the carrier body and the pad and covering the gap. The pad may be slideably disposed in the pocket.

A magneto-quasistatic field may be used to align hydrogen of materials within a structure and/or to disrupt the alignment of hydrogen of materials within the structure. Realignment of the hydrogen after the disruption may cause emission of energy from the hydrogen. The characteristic(s) of the energy may be detected and used to generate image(s) of interior portion(s) of the structure.

Apparatus and method are provided wherein by measuring both the electrical permittivity and the electrical conductivity of the measured multiphase fluid, the resultant amplitude and phase angle of the induced complex voltage can be analysed. The phase angle data can be analysed to provide information on the electrically conductive phase, and that information can be employed to analyse the amplitude data, in particular to use the information on the electrically conductive phase to determine the contribution to the amplitude data by the electrically non-conductive phase. This analytical technique enables the electrical permittivity of the electrically non-conductive phase to be accurately determined. By determining the degree of contribution to the complex voltage measurement by both the permittivity and the conductivity, enhanced measurement accuracy of a multiphase fluid can be achieved.

A magnetic susceptibility and conductivity tool (10) which incorporates a transmitter coil (4) energized with a time-varying current from a transmitter coil drive (13). The transmitter coil drive receives a clock signal and induces a data signal (99) including a primary mutual coupling signal and a formation coupling signal. A receiver coil (1) outputs a receiver coil voltage induced by the data signal. A transmitter coil current sense circuit (15) receives current from the transmitter coil and outputs a digital coil current voltage signal. A synthetic null circuit (14) receives the digital current voltage signal and multiplies the digital current voltage signal with a predetermined constant (28) for amplitude of a base primary mutual coupling signal and shifts phase with a predetermined phase offset (27) to output a synthetic null signal (104).

A magnetic susceptibility and conductivity tool (10) which incorporates a transmitter coil (4) energized with a time-varying current from a transmitter coil drive (13). The transmitter coil drive receives a clock signal and induces a data signal (99) including a primary mutual coupling signal and a formation coupling signal. A receiver coil (1) outputs a receiver coil voltage induced by the data signal. A transmitter coil current sense circuit (15) receives current from the transmitter coil and outputs a digital coil current voltage signal. A synthetic null circuit (14) receives the digital current voltage signal and multiplies the digital current voltage signal with a predetermined constant (28) for amplitude of a base primary mutual coupling signal and shifts phase with a predetermined phase offset (27) to output a synthetic null signal (104).

A drill hole logging system (5) incorporates a computing system (58) at the surface and a deployment mechanism (40) for conveying a logging tool (10) configured to measure one or more geophysical parameters into a drill hole (20). A transmission means (57) communicates commands and data representing the geophysical parameters between the surface computing system and the logging tool. A borehole caliper (300) is employed to profile the inside of the borehole.

A drill hole logging system (5) incorporates a computing system (58) at the surface and a deployment mechanism (40) for conveying a logging tool (10) configured to measure one or more geophysical parameters into a drill hole (20). A transmission means (57) communicates commands and data representing the geophysical parameters between the surface computing system and the logging tool. A borehole caliper (300) is employed to profile the inside of the borehole.

A computer-implemented method includes receiving a plurality of sensor signals, each signal of the plurality of sensor signals being tagged with an associated time and depth. The method also includes selecting a baseline signal. The method further includes comparing a selected sensor signal, of the plurality of sensor signals, to the baseline signal. The method also includes determining a difference between the baseline signal and the selected sensor signal exceeds a threshold. The method includes identifying, based at least in part on the difference, a feature of interest associated with the selected sensor signal.

Data filtering and processing techniques for generating improved wellbore resistivity maps are contemplated. In some aspects, a process of the disclosed technology includes steps for receiving a plurality of measurement sets, wherein each measurement set includes electromagnetic field data associated with a geologic formation, performing an inversion on each of the plurality of measurement sets to generate a corresponding plurality of formation profiles, and applying a filter to each of the formation profiles to generate a plurality of profile clusters. In some aspects, the process can further include steps for selecting a representative cluster from among the profile clusters for use in generating a wellbore resistivity map. Systems and machine-readable media are also provided.

Data filtering and processing techniques for generating improved wellbore resistivity maps are contemplated. In some aspects, a process of the disclosed technology includes steps for receiving a plurality of measurement sets, wherein each measurement set includes electromagnetic field data associated with a geologic formation, performing an inversion on each of the plurality of measurement sets to generate a corresponding plurality of formation profiles, and applying a filter to each of the formation profiles to generate a plurality of profile clusters. In some aspects, the process can further include steps for selecting a representative cluster from among the profile clusters for use in generating a wellbore resistivity map. Systems and machine-readable media are also provided.