Abstract: Measurements made by a multi-component induction logging tool are corrected for tool eccentricity in a deviated borehole. The eccentricity angle is determined from single frequency skin-effect corrected data and is then used to correct multifrequency data. Multifrequency focusing is then applied to the corrected multifrequency data. An inversion is then used to recover formation resistivity and relative dip and azimuth of the borehole.

Abstract: The present disclosure provides a method and apparatus for performing resistivity measurements of a borehole wall using a transverse octupole sensor. The sensor may be a resistivity sensor. Higher resolution is obtained with an octupole sensor than with lower-order-pole sensors. For the resistivity case, the ratio of dual-frequency measurements has reduced sensitivity to standoff.

Abstract: An apparatus, method and computer-readable medium for estimating a resistivity property of an earth formation in a borehole filled with oil-based mud. The method includes conveying a logging tool into a borehole; measuring a plurality of impedance values of the earth formation, each of the plurality of impedance values being obtained at one of a plurality of measure electrodes on the logging tool; determining a coefficient related to an electrical property of the mud from a plurality of pairs of impedance values; estimating the resistivity property of the formation from the determined coefficient; and recording the resistivity property on a suitable medium.

Abstract: A resistivity imaging device injects currents in two orthogonal directions using two pairs of return electrodes and performing impedance measurements of the buttons placed between the returns.

Abstract: A method for simulating a conductivity measured by a resistivity tool disposed in a borehole penetrating a formation, the method including: constructing a main grid extending from the borehole into the formation; constructing an auxiliary grid that is local to the main grid and fitted to a boundary between a first region having a first conductivity and a second region having a second conductivity; discretizing a problem operator on the auxiliary grid applying Maxwell's Equations to a volume represented by the auxiliary local grid, the Maxwell's Equations including a term representing the conductivity of a material in the volume; calculating one-dimensional functions for points on the auxiliary grid; constructing basic functions from the calculated functions; discretizing by the basic functions for points on the main grid; solving the resulting set of equations to obtain the simulated measured conductivity for the resistivity tool; and providing the simulated measured conductivity as output.

Abstract: An apparatus for imaging a subsurface material traversed by a borehole, the apparatus including an imaging pad deployed by a logging instrument, the pad including a plurality of measuring sets, each measuring set including a first current injector electrode, a second current injector electrode, a pair of sensor electrodes disposed between the first current injector electrode and the second current injector electrode, and an output for coupling to an electronics unit adapted for producing the imaging of the subsurface material.

Abstract: Measurements made by a multi-array/multi-frequency induction resistivity logging tool in a borehole are used for determining the length of fractures in an earth formation and the resistivity of the unfractured formation when the fractures have a resistive fluid. A look-up table based on modeling of a fracture by a pair of wings is used.

Abstract: An apparatus, method and computer-readable medium for evaluating an earth formation. A logging tool having a non-conductive mandrel and a conducting sleeve having at least one antenna that are electrically connected is conveyed into a borehole in the earth formation. At least one of the antennae has a coil oriented at a non-zero an angle to a longitudinal axis of the logging tool. The at least one antenna is activated, and an effect of a signal received by a receiver coil on the logging tool due to at least one of (A) an eccentering of the logging tool, and (B) a coil misalignment is reduced.

Abstract: A single-dipole sensor for determining an electrical property of an earth formation, includes a pad consisting essentially of a body and at least one small electrode separated from a large electrode by an insulator; wherein an output of the sensor includes a measurement of an electrical signal through the formation for each small electrode. A method for using the sensor is included, as well as a method for providing images of the earth formation.

Abstract: Measurements made by a four terminal resistivity imaging tool in a borehole using a voltage measurement device with two different input impedances. From the two measurements, formation resistivity is determined with minimal sensitivity to standoff. It is emphasized that this abstract is provided to comply with the rules requiring an abstract which will allow a searcher or other reader to quickly ascertain the subject matter of the technical disclosure. It is submitted with the understanding that it will not be used to interpret or limit the scope or meaning of the claims.

Abstract: A resistivity imaging apparatus includes: a first sensor electrode disposed on an electrode pad and positioned at a first standoff; a second sensor electrode disposed on the electrode pad and adjacent the first sensor electrode, the second sensor electrode positioned at a second standoff; and a return electrode disposed on the electrode pad, wherein the sensor electrodes and the return electrode are configured for injecting current into a formation and receiving a signal from the formation. Other embodiments, methods and computer program products are disclosed.

Abstract: A resistivity imaging device injects currents in two orthogonal directions using two pairs of return electrodes and performing impedance measurements of the buttons placed between the returns.

Abstract: A multicomponent induction logging tool uses a nonconducting mandrel. A central conducting member including wires that electrically connect at least one of the antennas to another of the antennas. Electrodes disposed about the transmitter antenna form a conductive path through a borehole fluid to the central conducting member.

Abstract: Phase-sensitive measurements are made by a resistivity imaging tool in a borehole having non-conductive mud in a conductive earth formation at a plurality of frequencies. From the phase sensitive measurements, the formation resistivity can be determined with higher sensitivity than is possible with the single frequency measurements. Tool standoff can also be determined from a knowledge of the mud resistivity and/or dielectric constant. Formation resistivity may also be determined when the effect of formation capacitance cannot be ignored.

Abstract: Impedance measurements made by a galvanic resistivity tool in a borehole in an earth formation are corrected by a factor that depends on the mud conductivity and the mud dielectric constant. Standoff measurements are not necessary.

Abstract: Measurements made by a resistivity imaging tool in a borehole having non-conductive mud in a conductive earth formation are corrected using the tool standoff. The correction involves removing a calibration signal determined in a medium of high conductivity from the measured impedance. The magnitude and/or the real part of the impedance may be used.

Abstract: A multicomponent induction logging tool uses a nonconducting mandrel with a windowed conducting sleeve. This arrangement reduces effects due to tool eccentering and coil misalignment.

Abstract: A resistivity imaging device injects currents in two orthogonal directions using two pairs of return electrodes and performing impedance measurements of the buttons placed between the returns.

Abstract: A mixed mode tool uses an inductive source and detects galvanic currents and/or potentials at electrodes in proximity to a borehole wall to produce a resistivity image of the earth formation. Alternative, the magnetic field produced by a galvanic current is detected by an antenna coil and used to produce a resistivity image. It is emphasized that this abstract is provided to comply with the rules requiring an abstract which will allow a searcher or other reader to quickly ascertain the subject matter of the technical disclosure. It is submitted with the understand that it will not be used to interpret or limit the scope or meaning of the claims.

Abstract: A mixed mode tool uses an inductive source and detects galvanic currents and/or potentials at electrodes in proximity to a borehole wall to produce a resistivity image of the earth formation.