Abstract: A method and system for resistivity imaging may comprise disposing a downhole tool into a borehole, wherein the downhole tool comprises a pad and a plurality of electrodes disposed on the pad, taking an impedance measurement with the plurality of electrodes, applying a correction to the measured impedance by using a relaxation constant of the measured impedance to find a corrected impedance for each electrode of the plurality of electrodes, and constructing an image from the corrected impedance, wherein the image maps formation impedance. The system for resistivity imaging may comprise a downhole tool, a conveyance for disposing the downhole tool in a borehole, and an information handling system. The downhole tool may further comprise an arm and a pad wherein the pad comprises a plurality of electrodes and at least one return electrode.

Abstract: Apparatus and methods can be implemented to monitor the condition of the production and intermediate casing strings in oil and gas field operations. A series of measurements can be made in a multi-pipe structure and received responses can be operated on by employing a mapping optimization procedure in which a surrogate model is updated. Estimates of one or more properties of the pipes of the multi-pipe structure can be generated using coefficients of the updated surrogate model. Additional apparatus, systems, and methods are disclosed.

Abstract: A method and system for estimating a mud angle. A method may include disposing a downhole tool into a borehole, energizing a button array, transmitting a current from the electrode into a formation, recording the current from the formation with a return electrode to obtain a plurality of measurements, identifying at least one low resistivity zone from the plurality of measurements to produce a measurement set, inverting the measurement set to find a mud angle vector, removing the mud angle vector from the measurement set to obtain a corrected measurement, and obtaining an electrical image using the corrected measurement. A system may include a downhole tool, a conveyance, and an information handling system. The downhole tool may further include at least one electrode and at least one return electrode.

Abstract: An improved measurement method and system particularly suited for graphite electrodes which correlates point cloud measurements collected from a CMM probe and laser scanner with an optimized model of the measured electrode to confirm the electrode is within tolerance or identify out of tolerance areas. The innovative method and system include a CMM probe either controlled by the operator or other forms of robotic automation, a laser scanner, and optimized models measured against the measured electrode and a computer server controlling a processing program for sorting and processing the collected measurements and optimized models. The described system and method therefore integrates a blend of technologies to precisely check the electrode for defects and to predict the performance within an electric arc furnace.

Abstract: A method of electrically logging a section of a wellbore includes circulating an oil-based wellbore fluid within the wellbore and allowing filtration of the oil-based wellbore fluid to form a conductive filtercake on a wall of the wellbore; placing within the wellbore a wellbore logging tool with at least one pad capable of applying a current to a portion of the conductive filtercake and wellbore wall; applying electrical current from the at least one pad; and collecting an electrical log of the portion of the wellbore that has had electrical current applied thereto.

Abstract: A variety of methods and systems are disclosed, including, a method for improving resistivity imaging, comprising: disposing a downhole tool into a borehole, wherein the downhole tool comprises a pad and a button array disposed on the pad; taking a measurement with the button array at a location in the borehole; selecting a projection angle; obtaining a corrected measurement from the projection angle and the measurement; and constructing an image using the corrected measurement. A system for improving resistivity imaging, comprising: a downhole tool, wherein the downhole tool comprises: an arm, and a pad; a conveyance; and an information handling system, wherein the information handling system is configured to take a measurement with the button array at a location in the borehole; select a projection angle; obtain a corrected measurement from the projection angle and the measurement; and construct an image using the corrected measurement.

Abstract: The disclosed embodiments include systems and methods to evaluate formation resistivity. In one embodiment, a method to evaluate formation resistivity proximate a wellbore is provided. The methods includes receiving data indicative of resistivity measurements of a formation proximate a wellbore at different distances within a range of distances from the wellbore. The method also includes analyzing the data to determine approximate formation resistivity of the formation at different distances from the wellbore. The method further includes generating at least one curve, each indicative of an approximate formation resistivity of the formation at the different distances from the wellbore, overlaying the at least one curve on a graph indicative of the formation resistivity of the formation within the range of distances from the wellbore, and providing the at least one curve overlaid on the graph for display on a device.

Abstract: In some embodiments, an apparatus and a system, as well as a method and an article, may operate to estimate a value for a mud cake parameter to provide an estimated mud cake parameter value; to generate, in a solution operation, a formation parameter value and an adjusted mud cake parameter value using the estimated mud cake parameter value; and to provide corrected galvanic tool resistivity measurements based on at least the adjusted mud cake parameter value. Additional apparatus, systems, and methods are disclosed.

Abstract: A method that includes deploying a casing with a multi-electrode configuration over a dielectric layer in a downhole environment. The method also includes collecting electromagnetic (EM) measurements using the multi-electrode configuration, and processing the EM measurements to obtain a characterization of fluids in an annulus between the casing and a borehole wall. A related system includes a casing deployed downhole, the casing having a multi-electrode configuration and a dielectric layer between the casing and the multi-electrode configuration. The system also includes a controller for directing collection of EM measurements using the multi-electrode configuration, and a processor that processes the EM measurements to obtain a characterization of fluids in an annulus between the casing and a borehole wall.

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: Method and articles for evaluating mud effect in imaging tool measurements are described. In an example, the method includes taking a plurality of measurements with a sensor positioned down a borehole, the sensor offset from a wall of the formation by a layer of mud, each measurement having an associated azimuth angle and depth. The plurality of measurements are related into a measurement set with each of the plurality of measurements having the same azimuth angle and depth within a designated depth range. The method includes determining, with a motion sensor, a relative position change of the sensor of each of the measurements within the measurement set and determining the offset of the sensor, one or more formation property, and one or more mud property.

Abstract: Models of fluid flow in wells in formation of a subsurface earth reservoir are formed by computers based on measurements obtained by well logging tools run in the wells and measurements of formation rock characteristics obtained from laboratory data. The models so formed are used to form measures of injection/production profiles and assist reservoir engineers in allocation of production and injection wells for the reservoir, and in other reservoir production planning and analysis.

Abstract: Methods of determining a spatial distribution of an injected tracer material within a subterranean formation are disclosed, including flowing the tracer material, which includes a tracer electrical capacitance that differs from a formation electrical capacitance of a region of the subterranean formation, into the region of the subterranean formation via a wellbore. Subsequent to the flowing, the methods also include providing an input electromagnetic signal to the region of the subterranean formation. Responsive to the providing, the methods further include receiving an output electromagnetic signal from the subterranean formation. The methods further include determining the spatial distribution of the tracer material within the subterranean formation based, at least in part, on the output electromagnetic signal.

Abstract: Apparatus and techniques are described, such as for obtaining information indicative of a formation resistivity, such as using an array laterolog apparatus. For example, an electrical excitation is coupled from a well tool in a borehole to a geologic formation through which the borehole extends, the excitation coupled through excitation electrodes on the well tool selected according to a specified excitation mode, and induced voltages are received from the geologic formation resulting from the excitation using monitor electrodes selected according to the specified excitation mode. In some examples, a voltage difference between a first pair of monitor electrodes is estimated through use of the induced voltage received through at least one additional monitor electrode.

Abstract: Apparatus and methods operable to determine a resistivity of a subterranean formation surrounding a wellbore. One such method includes using an apparent impedance function depending on a frequency variable and a plurality of unknown parameters, at least one of the unknown parameters depending on a formation impedance of the subterranean formation. The method also includes applying a voltage, at each of a plurality of frequency values, between electrodes of a resistivity tool that is disposed in the wellbore. The method also includes measuring, across the electrodes, a plurality of apparent impedance values, each corresponding to a different one of the frequency values. The method still further includes determining the unknown parameters based on the frequency values and the apparent impedance values, and estimating the formation resistivity based on an expression that includes at least one of the unknown parameters.

Abstract: An electromagnetic field measuring device utilizes metamaterials to manipulate electromagnetic fields. Such a device is useful in a variety of applications including, for example, downhole gradiometric ranging.

Abstract: Methods, systems, and devices for evaluating an earth formation intersected by a borehole using information from standard resolution measurements. Methods include generating an image representative of the formation over an interval of borehole depth, the image having a second resolution greater than the first resolution. Generating the image may be carried out by identifying layers corresponding to lithotype facies within the interval, the layers defined by boundaries having boundary locations along the borehole; and using a unified characterization of the formation within the interval determined from the standard resolution measurements and the boundary locations within the interval to solve for a value for the formation parameter corresponding to each layer consistent with the unified characterization of the interval. The unified characterization may be an average value for the formation parameter within the interval.

Abstract: In some embodiments, an apparatus, system, and method may operate to transmit a current from an electrode at a first azimuthal location into a borehole wall in a geological formation, and to receive the first current at a second electrode at a second azimuthal location in the borehole wall. The first and second azimuthal locations are disposed approximately along the same longitudinal location of the borehole wall. The current may be adjusted to maintain a selected voltage profile between the electrodes at the first and second azimuthal locations, and the electrodes at the first and second azimuthal locations may be members of two different sets of azimuthally] differentiated electrodes. Additional apparatus, systems, and methods are disclosed.

Abstract: A method and a resistivity image logging tool connected or connectable to one or more processing devices process geological log data to construct missing information from destroyed or occluded parts using cues from observed data. The geological log data signals can be generated through use of the logging tool having one or more electrodes interacting with a formation intersected by a borehole. The processing involves the steps of: in respect of one or more data dimensions associated with missing values in a log data set, decomposing the signal into a plurality of morphological components; and morphologically reconstructing the signal such that missing values are estimated.

Abstract: A method for signal communication between a well drilling instrument and the Earth's surface includes generating an electromagnetic field in an instrument disposed in drill string used to drill a wellbore. The electromagnetic field comprises encoded measurements from at least one sensor associated with the instrument. A signal is measured corresponding to an amplitude, phase or frequency of the electromagnetic field. The measurements are decoded from the measured signal. The measured signal comprises at least one of a voltage imparted across a capacitive electrode proximate ground surface and a galvanic electrode in contact with the ground surface, and a voltage imparted across two capacitive electrodes each proximate a ground surface and separated from each other by a known distance.

Abstract: The invention relates to measuring and generating electrical fields downhole. In one embodiment a system is provided that includes an amplifier connected to a first electrode in electrical contact with the Earth via an operative capacitive coupling. An additional electrode and amplifier are disposed in the borehole opposite the first electrode and constitute a first pair of electrodes spaced in a direction orthogonal to the axis. A second electrode is part of a group of counter electrodes spaced from each other and disposed outside the borehole. The first pair of electrodes and the amplifiers are configured to be one of a source that generates an electrical field in a direction substantially orthogonal to the axis of the borehole and a sensor that measures an electric field substantially orthogonal to the axis of the borehole.

Abstract: An example method for downhole surveying and measuring may include receiving a measurement from a receiver of a conformable sensor, the measurement corresponding to a response of a downhole element to an electromagnetic signal generated by a transmitter of the conformable sensor. A parameter of the downhole element may be determined based, at least in part, on the received measurement. A visualization of a feature of the downhole element may be generated based, at least in part, on at least one of the received measurement and the determined parameter.

Abstract: Disclosed embodiments include well ranging apparatus, systems, and methods which operate to measure electromagnetic field strength components associated with an electromagnetic field originating at a first well, via direct transmission or backscatter transmission, using at least one ranging electromagnetic field strength sensor attached to a housing, to provide ranging measurements. Further activities may include obtaining distorting field strength measurements using one or more reference electromagnetic field strength sensors, which may form or be attached in a closed loop path around the housing; and determining an approximate range between the first well and a second well in which the ranging electromagnetic field strength sensors are disposed, based on the ranging measurements and the distorting field strength measurements. Additional apparatus, systems, and methods are disclosed.

Abstract: Probes for an inspection system for a substantially round hole in a material are provided. One version of the probe may include a flexible sheet shaped and biased to substantially conform with a portion of an interior of the substantially round hole; and a plurality of sensors disposed on the flexible sheet, each sensor configured to transmit a non-destructive signal into the material for inspecting the substantially round hole.

Abstract: An apparatus and method for estimating the at least one resistivity parameter using at least one processor to estimate capacitance information, wherein the capacitance information is estimated using only one selected frequency electromagnetic signal. The apparatus may include at least one measure electrode. The apparatus may also include a transverse antenna. The method may include imparting an electric current at only one selected frequency into a formation using the at least one measure electrode. The method may also include using capacitance information to estimate a standoff between the at least one measure electrode and a borehole wall. In some embodiments, the estimated capacitance information may be used to reduce errors due to eccentricity.

Abstract: Multi-array laterolog tool systems and methods acquire a set of array measurements sufficient to provide laterolog tool measurements of differing array sizes. Such systems and method offer multiple depths of investigation while offering greater measurement stability in borehole environments having high resistivity contrasts. In at least some system embodiments, a wireline or LWD tool body has a center electrode positioned between multiple pairs of guard electrodes and a pair of return electrodes. At least some of the guard electrodes are positioned between component electrodes of associated split monitor electrodes that enable more accurate measurement of the guard electrode potential. The tool's electronics provide a current from the center electrode to the pair of return electrodes and currents from each pair of guard electrodes to the pair of return electrodes. Each of the currents may be distinguishable by frequency or distinguishable by some other means.

Abstract: The invention is concerned with a tool and method for determining standoff from a formation though mud. The tool comprising a first electrode located at a distance from the formation for measuring a first impedance. A second electrode is located at a second distance from the formation for measuring a second impedance. A processing unit measures a difference between the first impedance and the second impedance, uses the difference to determine a conductivity of the mud and based thereon, determines the standoff of at least one of the first and the second electrode.

Abstract: Resistivity in subsurface earth at locations kilometers away from wells in the reservoirs is mapped and monitored. An electromagnetic source with an electrode is deployed a borehole in the reservoir, and a group of sensors at counter electrodes is deployed at a number of other locations radially spaced at some distance from the well. The source transmits a current which flows to the counter electrodes causing an electromagnetic field which is sensed at the sensors. The source is activated at different depths in the well and ratios of the electromagnetic field sensed with the source at different depths used to obtain data to map the resistivity. The sensors are capable of sensing electromagnetic fields along two orthogonal axes, and the measurements at a sensor along these axes used to reduce undesirable effects of noise and other factors on the data measurements.

Abstract: Errors produced in a borehole to surface electromagnetic (BSEM) survey by near surface electrical anomalies on the estimates of formation properties are reduced. The effects of variations in subsurface electrical resistivity near the surface are separated from electrical resistivity changes at locations in the formations of interest far from the measurement region. A survey system includes one or more electrodes to inject electrical current at formation depth within a borehole, one or more counter electrodes which collect such current on the surface of the earth, and one or more electrodes to inject current on the surface. A transmitter is selectively connectable to different sets of the electrodes to cause a current to flow between the selected electrode sets. The resultant fields from the current flow are sensed and processed. The effects of near surface anomalies are detectable in the data and removable from the survey data of interest regarding the formations.

Abstract: Disclosed is an apparatus for estimating a property of an earth formation penetrated by a borehole containing an oil-based drilling fluid. The apparatus includes an electrode disposed at a carrier and configured to inject alternating current into the formation. An electrically conductive plate is disposed between the first electrode and a borehole wall. An electrical insulator is disposed between and contacts the first electrode and the conductive plate. The apparatus is configured to prevent the drilling fluid from being disposed between the first electrode and the conductive plate. A first sensor is used to measure an electric field established between the first electrode and the conductive plate. A processor is configured to receive a measurement of the electric field to use as a floating reference signal to determine a phase difference with respect to a measured electrical quantity related to the injected electrical current in order to estimate the property.

Abstract: Disclosed is an apparatus for estimating a property of an earth formation penetrated by a borehole. The apparatus includes a plurality of electrodes disposed downhole and configured to inject an electrical current into the earth formation using an applied voltage and/or measure electrical current resulting from an injection of the electrical current. The apparatus also includes a processor configured to perform a series of formation measurements that include injecting current into the earth formation using a unique subset of electrodes in the plurality of electrodes and measuring current in the earth formation using one or more electrodes not used for the current injecting. The processer sums the measured currents for the electrodes wherein the sum of electrical currents for at least one electrode that measured electrical current is substantially in phase with the applied voltage; and uses the sum of in phase currents to estimate the property.

Abstract: Multi-array laterolog tool systems and methods acquire a set of array measurements sufficient to provide laterolog tool measurements of differing array sizes. Such systems and method offer multiple depths of investigation while offering greater measurement stability in borehole environments having high resistivity contrasts. In at least some system embodiments, a wireline or LWD tool body has a center electrode positioned between multiple pairs of guard electrodes and a pair of return electrodes. The tool's electronics provide a current from the center electrode to the pair of return electrodes and currents from each pair of guard electrodes to the pair of return electrodes. Each of the currents may be distinguishable by frequency or distinguishable by some other means. This novel arrangement of currents provides a complete set of measurements that enables one tool to simultaneously emulate a whole range of laterolog tools.

Abstract: The invention is concerned with a tool for imaging a formation, the tool comprising: a pad capable of alignment adjacent a wall of the formation. The pad has located thereon an imaging electrode for injecting current into the formation. There is a first return electrode separated from the imaging electrode for receiving the injected current. There is at least one recessed electrode that is located at a different distance from the wall of the formation as the other electrodes.

Abstract: The invention is concerned with a tool and method for imaging a formation through a substantially non-conductive medium. The tool comprises first circuitry for injecting a current into the formation, wherein a complex impedance to the current is measured. Second circuitry for determining a phase angle of an impedance of the non-conductive medium and third circuitry for determining a component of the complex impedance that is orthogonal to the phase angle.

Abstract: The invention is concerned with a tool and method for determining a downhole parameter. The tool is located in mud surrounded by a formation and comprising a first electrode spaced at a distance from the formation for measuring a first impedance. There is a second electrode located at a second distance from the formation for measuring a second impedance. There is a processing unit for measuring a difference between the first impedance and the second impedance and wherein the parameter is determined based on the difference.

Abstract: System and methods of generating calibrated downhole images of a subterranean formation (110) surrounding a wellbore (105). The method involves measuring open hole and cased hole measurements with a downhole tool (132); determining (698) open hole parameters (e.g., Z90) from the cased hole parameters, known parameters and the open hole measurements; and generating (699) downhole outputs from the determined open hole parameters.

Abstract: Multi-array laterolog tool systems and methods acquire a set of array measurements sufficient to provide laterolog tool measurements of differing array sizes. Such systems and method offer multiple depths of investigation while offering greater measurement stability in borehole environments having high resistivity contrasts. In at least some system embodiments, a wireline or LWD tool body has a center electrode positioned between multiple pairs of guard electrodes and a pair of return electrodes. At least some of the guard electrodes are positioned between component electrodes of associated split monitor electrodes that enable more accurate measurement of the guard electrode potential. The tool's electronics provide a current from the center electrode to the pair of return electrodes and currents from each pair of guard electrodes to the pair of return electrodes. Each of the currents may be distinguishable by frequency or distinguishable by some other means.

Abstract: An apparatus for estimating a property of an earth formation penetrated by a borehole, apparatus including: a carrier configured to be conveyed through the borehole; a transducer disposed at the carrier and configured to transmit and/or receive electromagnetic energy into and/or from the earth formation to estimate the property; wherein the transducer includes a plurality of inductively coupled elements in a series, each element configured to transmit and/or receive electromagnetic energy and at least a first connection to a first element in the plurality and a second connection to a second element in the plurality with at least one of the first element and the second element being disposed between end transducer elements in the series.

Abstract: A method and a system for providing electromagnetic measurement in a rock formation are provided. The system includes a borehole casing having a plurality of casing segments. At least two casing segments of the plurality of casing segments are electrically isolated from each other. The system further includes an electromagnetic source positioned on a surface of the earth. The electromagnetic source is connected to the at least two casing segments. The electromagnetic source is configured to energize the at least two casing segments so as to generate an electromagnetic field in the rock formation around the borehole casing.

Abstract: A valve position sensor of a sliding sleeve of a flow control valve comprising a sleeve displacement converting means for converting a sleeve displacement into a radial displacement, and a measuring means for detecting the radial displacement and correlating the radial displacement to the position of the sliding sleeve within the flow control valve.

Abstract: A system and method for imaging properties of subterranean formations in a wellbore is provided. The system comprises a formation sensor for collecting currents injected into the subterranean formations, the formation sensor positionable on a downhole tool deployable into the wellbore. The system comprises a controller for controlling the formation sensor and a formation imaging unit. The formation imaging unit comprises a current management unit for collecting data from the currents injected into the subterranean formations, the currents having at least two different frequencies. The formation imaging unit comprises a drilling mud data unit for determining at least one drilling mud parameter, a formation data unit for determining at least one formation parameter from the collected data, and an inversion unit for determining at least one formation property by inverting the at least one formation parameter.

Abstract: Techniques related to making resistivity measurements of an underground formation surrounding a borehole involve using a tool having an insulating pad mounted on the conductive body of the tool. The pad has a current injector electrode and a current return electrode electrically isolated from each other and mounted on a face of the pad. The pad is positionable in use to be adjacent the wall of the borehole. At least two impedance ratios are determined. The first is the ratio of the electrical impedance between the current injector electrode and the tool body and the electrical impedance between the current return electrode and the tool body. The second is the ratio of the electrical impedance between the current injector electrode and the formation, and the electrical impedance between the current return electrode and the formation on the other hand.

Abstract: A system and method for imaging properties of subterranean formations in a wellbore is provided. The system comprises a formation sensor for collecting currents injected into the subterranean formations, the formation sensor positionable on a downhole tool deployable into the wellbore. The system comprises a controller for controlling the formation sensor and a formation imaging unit. The formation imaging unit comprises a current management unit for collecting data from the currents injected into the subterranean formations, the currents having at least two different frequencies. The formation imaging unit comprises a drilling mud data unit for determining at least one drilling mud parameter, a formation data unit for determining at least one formation parameter from the collected data, and an inversion unit for determining at least one formation property by inverting the at least one formation parameter.

Abstract: Disclosed is an adaptive borehole correction (ABC) technique based on an inversion approach that advantageously corrects shallow laterolog measurements for borehole effects, including determining and accounting for unknown tool eccentricity. The algorithm is based on simplex radial 1-D inversion where at every logging up to four unknowns are determined, namely tool eccentricity, Rt, Rxo, and Lxo. After that a borehole correction methodology is employed wherein the tool response in a borehole with real mud resistivity Rm is modified to a response in the borehole with virtual mud resistivity equal to Rxo.

Abstract: Techniques related to making resistivity measurements of an underground formation surrounding a borehole involve using a tool having a pad mounted on the body of the tool. The pad has a current injector electrode and a current return electrode mounted on the pad face and arranged such that the current injector and return electrodes are electrically isolated from each other when in use. Two impedance ratios are determined. The first is a ratio of the electrical impedance between the current injector electrode and the tool body, and the electrical impedance between the current return electrode and the tool body. The second is a ratio of the electrical impedance between the current injector electrode and the formation, and the electrical impedance between the current return electrode and the formation. The tool is arranged such that the two impedance ratios differ by 25% or less of the larger impedance ratio.

Abstract: A method analyzes a subterranean formation. At least one property of a well casing in the subterranean formation is determined and a plurality of current source vectors at respective positions along a trajectory of the well casing are determined. The effect of the well casing is determined based upon the plurality of current source vectors and the at least one property of the well casing.

Abstract: An apparatus and method for conducting resistivity logging in a borehole. The apparatus may include a housing configured for fluid isolation, an electrical conductor penetrating the housing and a sealing interface. The apparatus may also include at least one of: an electrical component inside the housing and an electrode disposed on the exterior of the housing. The apparatus is configured to allow the electrical conductor to be moved, while maintaining the sealing interface, between an electrically connected state and an electrically disconnected state with at least one of: the electrical component and the electrode. The method may include using the apparatus for resistivity logging operations.

Abstract: A method of treating a subsurface formation includes circulating at least one molten salt through at least one conduit of a conduit-in-conduit heater located in the formation to heat hydrocarbons in the formation to at least a mobilization temperature of the hydrocarbons. At least some of the hydrocarbons are produced from the formation. An electrical resistance of at least one of the conduits of the conduit-in-conduit heater is assessed to assess a presence of a leak in at least one of the conduits.

Abstract: A formation measurement and processing technique which reduces the effects of standoff between a resistivity tool and a borehole wall where the resistivity tool utilizes capacitive coupling between the tool and the formation to obtain resistivity data useful to generate a resistivity image of the formation. Reduction of standoff effects is achieved through the use of multi-frequency, phase sensitive measurements to identify a measured resonance frequency that may be used to produce an image that utilizes measurements least affected by the tool standoff and unknown or unspecified inductance of the tool. Reduction of standoff effects are the most pronounced in the case of the low resistivity formations and oil-based, low-conductive drilling fluids.

Abstract: Disclosed is an apparatus for estimating a property of an earth formation penetrated by a borehole having a substantially non-conducting liquid. The apparatus includes: a downhole tool having a transmitter electrode configured to convey an electric current into the earth formation. A measurement electrode is configured to receive the electric current from the earth formation, wherein the electric current bridges as least one of a first gap between the transmitter electrode and the formation and a second gap between the measurement electrode and the formation. A compensating circuit coupling the transmitter electrode to the measurement electrode is configured to reduce a reactive component of a total current received by the measurement electrode. A receiver coupled to the measurement electrode is configured to measure the total current to estimate the property.