Abstract: System and method for controlling the drilling of a second wellbore in close proximity to a first well bore. A computer system obtains information regarding a previously drilled wellbore, as well as information regarding a second wellbore being drilled. Using information obtained from one or more magnetic sensors, the computer system determines an optimal target path for continued drilling of the second wellbore and may issue one or more control signals to one or more control systems coupled to a drilling rig to automatically drill in accordance with the selected path. The computer system can generate a plurality of potential paths using one or more cost curves and/or value curves to determine the optimal path for the second wellbore.

Abstract: Aspects of the subject technology relate to systems and methods for identifying values of mud and formation parameters based on measurements gathered by an electromagnetic imager tool through machine learning. One or more regression functions that model mud and formation parameters capable of being identified through an electromagnetic imager tool as a function of possible tool measurements of the electromagnetic imager tool can be generated using a known dataset associated with the electromagnetic imager tool. One or more tool measurements obtained by the electromagnetic imager tool operating to log a wellbore can be gathered. As follows, one or more values of the mud and formation parameters can be identified by applying the one or more regression functions to the one or more tool measurements.

Abstract: A method for identifying an operating frequency may comprise performing a frequency sweep using one or more injector electrodes disposed on a downhole tool, recording one or more measurements from the frequency sweep, identifying one or more stable frequencies from the frequency sweep, and identifying one or more operating frequencies from the one or more stable frequencies. A system for electrical isolation may comprise a downhole tool, a pad, an arm, wherein the arm is attached to the mounting bracket and the mandrel, and an information handling system connected to the pad through the first set of electronics and the second set of electronics. The downhole tool may comprise a mandrel, a chassis disposed in the mandrel, and a first set of electronics disposed in the chassis.

Abstract: A method and a system for tuning a pad. The method may comprise disposing a downhole tool into a borehole, configuring the pad in a first configuration, taking a first measurement of the formation in the first configuration, configuring the pad in a second configuration, taking a second measurement of the formation in the second configuration, determining a tuning coefficient to reduce a tool body effect in the first measurement and the second measurement, computing a first weighted measurement from the tuning coefficient and the first measurement, computing a second weighted measurement from the tuning coefficient and the second measurement, and computing a tuned impedance from a ratio of the first weighted measurement and the second weighted measurement. A system for determining a formation boundary may comprise a downhole tool, an arm, and a pad. The system may further comprise a conveyance and an information handling system.

Abstract: A logging tool having a transmitter and receiver is positioned in a geological formation. While the logging tool is static, a transmit input signal is applied to a transmitter to cause the transmitter to induce a transmit output signal in the form of an electromagnetic field into a formation. While the logging tool is static, a formation signal is received based on the transmit output signal. The formation signal may be a voltage indicative of an induced polarization in the formation based on the transmit output signal. A complex resistivity of the formation is determined based on the formation signal.

Abstract: A method of electrically logging a section of a wellbore includes circulating an oil-based wellbore fluid comprising a conductive carbon material therein, the oil-based wellbore fluid having a conductivity of at most 0.01 S/m when measured at 20 kHz, within the wellbore while drilling the wellbore with a drill bit on a drill string; applying electrical current from a logging tool on the drill string above the drill bit; and collecting an electrical log of the portion of the wellbore that has had electrical current applied thereto.

Abstract: A system is provided for generating a ramping signal. The system includes a plurality of storage circuits each including an input and an output. The output of a previous storage circuit is connected to the input of a next storage circuit. The storage circuits are configured to propagate a first enable signal based on a first control signal. The system also includes a plurality of first current generating circuits. Each first current generating circuit is coupled to the output of a corresponding storage circuit to receive the propagated first enable signal. The first current generating circuits are configured to generate a first current signal based on the propagated first enable signal.

Abstract: Apparatus and techniques are described, such as for obtaining information indicative of a formation resistivity near a casing, such as using an array laterolog apparatus. For example, raw measurements received from a well tool in a borehole near a casing may indicate a resistivity of a geologic formation through which the borehole extends. Any errors or interference in the raw measurements caused by the proximity of the well tool to the casing may be removed to eliminate the casing effect on the raw measurements. In some examples, a signal and formation libraries that include casing specific parameters may be used in conjunction with non-casing optimized signal and formation libraries to perform correction mapping of raw measurements. The corrections and their application to the raw measurements may be based on the position of a well logging tool with respect to a casing termination point.

Abstract: Systems and methods that relate to monitoring a subterranean formation using casing centralizers. A system for well monitoring comprising: a casing centralizer comprising arms configured to contact a wellbore when the casing centralizer is installed in a wellbore; and a receiver coupled to the casing centralizer and configured to measure an electrical magnitude of a current injected into a subterranean formation through the arms of the casing centralizer.

Abstract: A method for determining a diagnostic condition of a vehicular video connection includes providing a video driver, a video cable, a video driver power supply, a current sensor and a microcontroller. The video driver is powered via the video driver power supply. Current flowing to the video driver from the video driver power supply is sensed via the current sensor. The microcontroller determines a current level sensed by the current sensor during operation of the video driver. An open circuit condition may be determined when the determined current level of the current flowing into the video driver falls below a predetermined quantity, and/or a short to battery condition may be determined when the determined current level of the current flowing into the video driver exceeds a predetermined quantity.

Abstract: Electrically conductive oil-based wellbore fluids and methods of using same are provided. Wellbore fluids provided may contain one or more carbon nanotubes, where the one or more carbon nanotubes have a particular d/g ratio as determined by Raman spectroscopy. Also provided are methods for electrical logging of a subterranean well that include emplacing a logging medium into a subterranean well, wherein the logging medium contains a non-aqueous fluid and one or more carbon nanotubes, where the one or more carbon nanotubes are present in a concentration so as to permit the electrical logging of the subterranean well; and acquiring an electrical log the subterranean well.

Abstract: An example method may include computing a database for an ideal representation of a galvanic tool, and determining internal coupling impedance between at least one monitor electrode of the galvanic tool and a reference. Voltage and current measurements from the galvanic tool positioned within a formation may be received. A formation resistivity from the voltage and current measurements may be calculated based, at least in part, on the database and the determined internal coupling impedances.

Abstract: An arrangement for generating a resistivity image having a drill bit with cutters configured to be placed within a wellbore, the cutters configured to create further sections of the wellbore upon rotation, the drill bit having an end with threads for engagement, at least one section of drill string connected to the drill bit through a matching set of threads for engagement, a receiver toroid connected to the at least one section of drill string along at least a portion of the drill string, a transmitter toroid connected to the at least one section of drill string and located at least a portion of the drill string away from the receiver toroid, at least one stabilizer connected to the at least one section of drill string, a power source connected to the transmitter toroid and the receiver toroid, an electrode arrangement placed at the drill bit, wherein the electrode arrangement is electrically connected to the drill bit through a non-linear circuit element and a computer arrangement connected to the receiver

Abstract: A resistivity logging tool includes a plurality of excitation electrodes, at least one return electrode, and a plurality of monitor electrodes. The resistivity logging tool also includes a controller that determines a set of independent currents to be emitted by at least some of the plurality of excitation electrodes during an excitation cycle based on at least one measured downhole parameter and at least one predetermined constraint.

Abstract: A system for spectral induced polarization measurement of a formation is provided. The system provides an intelligent module to be utilized in performing spectral induced polarization (SIP) measurements for geophysical studies or otherwise. The system includes a instrument that includes a housing configured to be inserted into a surface opening. The housing houses a signal generator that generates an excitation signal. A drive electrode directs the excitation signal into the material adjacent the housing. A plurality of electrodes sense the voltage and/or current in the material adjacent the housing and a processor processes the sensed voltage and/or current to measure a property of the material. The system also provides a configuration in which a plurality of instruments configured for spectral induced polarization measurements are interconnected to provide communication, synchronization, a common reference signal or power.

Abstract: Disclosed are methods and systems that include a multiple-tube electrode assembly. An embodiment discloses an electrode assembly, comprising: a carrier body comprising an elongated support; and electrically conducting surfaces longitudinally spaced along the carrier body, wherein the electrically conducting surfaces are electrically coupled in parallel.

Abstract: A method is provided to transmit an error-correcting code. The method includes receiving a source packet, advancing a sliding encoder window after receiving the source packet, and generating coded packets by, when the padded packet is encoded for a first time, encoding the source packet alone, and, when the source packet is encoded for a number of times after the first time, encoding the source packet with older source packets in the sliding window.

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: A method and apparatus are provided for making directional measurements toward a formation of different resistivity that is proximate to the borehole, but which is not penetrated by the borehole. The methods and apparatus include the use of at least one insulated gap and at least one magnetometer positioned within a non-magnetic housing that is disposed within a non-magnetic tubular. An electric current is applied across the insulated gap, which results in current leaking into the surrounding formations. When a formation of contrasting resistivity is proximate to the logging apparatus, the magnetometer detects a secondary magnetic field due to the contrasting formation. The direction of the secondary magnetic field can be used to determine the direction to the contrasting formation. The magnitude of the secondary magnetic field can be used to determine the distance position to the contrasting formation.

Abstract: An oil-based mud formation imaging tool for measuring electrical properties of surrounding formation includes at least one base plate, a first port and a second port deployed on the base plate, surface conductors covering both sides of the base plate, and inside conductors deployed in the first port and the second ports and with gaps from the edges of the first and second ports. The first port is fed with electromagnetic signals by a waveguide and a coupling is formed between the imaging tool and the surrounding formation accordingly. Resonance signals are induced at the second port to be used to compute corresponding formation resistivity and dielectric constant. A corresponding imaging method is also provided.

Abstract: In some embodiments, an apparatus and a system, as well as a method and an article, may operate to monitor a first condition associated with transmitting or receiving a signal in a formation or on a drill string, or both, over a first selected interval of a drill string located down hole; to monitor a second condition associated with transmitting or receiving the signal in the formation or on the drill string or both, over a second selected interval of the drill string; to compare the first condition to the second condition to provide a comparison result; and based on the comparison result, to select one of the first selected interval or the second selected interval to transmit or receive the signal in the formation or on the drill string, or both. Additional apparatus, systems, and methods are disclosed.

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: In some embodiments, a method of approximating or determining at least one dimension of at least one underground geological feature in a zone of interest proximate to a well bore includes generating an electric field in the zone of interest while the well bore and geological feature at least partially contain conductive fluid. At least two sensing electrodes are provided in the well bore and configured to detect differences therebetween in electric potential caused by at least one target object in the zone of interest and provide data relating thereto to at least one data processing system. The data processing system(s) approximates or determines the dimension(s) of the geological feature(s) based at least partially upon data provided by the sensing electrodes.

Abstract: Various techniques for generating a polar display include a method, which involves receiving information identifying a formation property of an anomaly within a geologic formation from a measurement-while-drilling (MWD) tool that includes several sensors. The formation property is identified by at least one magnitude and at least one distance. The formation property is also identified relative to a corresponding property of the geologic formation. The method also involves receiving information identifying an azimuthal angle from the MWD tool, where the azimuthal angle relates a position of the anomalous formation to a position of a first sensor. The method then generates a graphic, based upon the at least one magnitude and the at least one distance and the azimuthal angle, and displays the graphic on a polar display, in which a center of the polar display corresponds to a location of the borehole in which the MWD tool is located.

Abstract: Disclosed is a method for estimating a property of an earth formation penetrated by a borehole. The method includes: transmitting acoustic waves into the formation from an acoustic source disposed in the borehole and away from a wall of the borehole; generating radial acoustic eigenwaves within a space between the wall of the borehole and the acoustic source using the transmitted acoustic waves; receiving an acoustic signal with an acoustic receiver disposed at the wall of the borehole; sensing an electric field signal with an electric field sensor disposed at the wall of the borehole; and estimating the property using the received acoustic signal and the sensed electric field signal.

Abstract: A method and apparatus is provided for collecting reservoir data. The method includes providing one or more electromagnetic sources for generating an electromagnetic field in a reservoir and providing one or more electromagnetic sensors equipped with capacitive electrodes. The electromagnetic source is located separately from the electromagnetic sensor. The electromagnetic sensor may either be located within a well or at the surface, is capable of measuring the electromagnetic field in three dimensions, and may be isolated from the well fluids. The data collected by the electromagnetic sensors can be used to create a model of the oil reservoir, including the water saturation.

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: A method of approximating or determining at least one dimension or other characteristic of at least one underground geological feature in a zone of interest proximate to a well bore includes generating an electric field in the zone of interest. At least two sensing electrodes are provided in the well bore and configured to detect differences therebetween in electric potential caused by at least one target object in the zone of interest. Proppant containing signal generating devices (SGD) is delivered into the geological feature(s). The SGD generate a detectable signal in response to at least one downhole condition or property. At least one receiver receives the detectable signals and provides data relating thereto. At least one dimension or other characteristic of the geological feature is approximated or determined based at least partially upon data provided by the sensing electrodes and receiver(s).

Abstract: The invention provides a method of receiving and/or transmitting information in a well drilled in a geological formation between a first location and a second location, the well comprising a casing communicating with the geological formation. The method comprises placing a first transducer at a first location, placing a second transducer at a second location. Transmitting an electric signal between the first and second transducers.

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: A self-powered borehole communication assembly including a first electrode member having a first electrode potential and a second electrode member having a second electrode potential different than the first electrode potential. The first and second electrodes form an electrochemical cell when disposed in a borehole fluid that is at least partially electrolytic. The electrochemical cell is operatively arranged for producing a current and a voltage with at least one of the current or the voltage configured to directly convey information related to at least one borehole condition, property, or parameter. A method of communicating is also included.

Abstract: A method of monitoring an extent of a hydrocarbon reservoir (2) below the earth's surface (4), includes the steps of applying a current between a bottom current electrode (6) and a top current electrode (8) that is part of a plurality of electrodes that are spaced apart from one another along a part of the earth's surface located above and optionally over the hydrocarbon reservoir. The bottom current electrode is positioned below the hydrocarbon reservoir. The method includes the step of measuring an electrical potential, which is caused by the current, by means of a measurement electrode (10A) that is also part of the plurality of electrodes. The method includes the step of inferring from the measured electrical potential the extent of the hydrocarbon reservoir, in a direction that is oriented substantially parallel with the earth's surface.

Abstract: A microresistivity logging tool includes a monopole current injection electrode and at least first and second pairs of potential electrodes. The tool may further include a controller configured for making microresistivity anisotropy measurements using a single firing of the monopole current injection electrode. The controller may be configured to compute a two-dimensional tensor of the local formation resistivity from a single firing of the monopole current injection electrode. The use of a single firing tends to decrease measurement time, which in turn tends to improved azimuthal sensitivity in microresistivity anisotropy imaging while drilling applications.

Abstract: A microresistivity logging tool includes a monopole current injection electrode and first and second potential electrodes deployed on a downhole tool body. A controller is configured to apply a high frequency alternating current between the monopole current injection electrode and a return and measure a corresponding AC potential difference between the first and second electrodes.

Abstract: A steerable, magnetic dipole antenna for Measurement-While-Drilling (MWD) or Logging-While-Drilling (LWD) applications. The antenna elements use a hole arrangement in addition to grooves in a steel tool body, which is typically a drill collar. This antenna embodiment is extremely robust, meaning that does not significantly reduce the structural integrity of the tool body in which it is disposed. The antenna embodiment is also relatively wear resistant. The resultant magnetic dipole generated by this antenna is also electrically steerable in inclination angle from a common origin. A variable dipole moment inclination angle combined with independently measured tool rotation orientation during normal drilling allows the antenna to generate a magnetic dipole moment that may be directed at any three dimensional angle and from a common origin point at the centroid of the antenna. The antenna can also be embodied to be more sensitive to resitivity in a particular azimuthal direction.

Abstract: A machine, computer program product, and method to enable scalable parallel reservoir simulations for a variety of simulation model sizes are described herein. Some embodiments of the disclosed invention include a machine, methods, and implemented software for performing parallel processing of a grid defining a reservoir or oil/gas field using a plurality of sub-domains for the reservoir simulation, a parallel process of re-ordering a local cell index for each of the plurality of cells using characteristics of the cell and location within the at least one sub-domain and a parallel process of simulating at least one production characteristic of the reservoir.

Abstract: An apparatus and method for reducing an electric current leakage in a logging tool, particularly relating to reducing electric current leakage by altering a phase difference between a biasing element and an electric current produced by a first power source. The apparatus may include one or more measure electrodes for imparting electric current into a formation, a current meter, at least one current return electrode, a controller, and a biasing element. The method includes adjusting a phase angle difference between the current leaving the measure electrode and a biasing signal applied to the biasing element from a second power source to reduce the current leakage of the apparatus.

Abstract: A system for measuring a resistivity parameter of an earth formation includes: at least one measurement electrode electrically connected to a first electrical source; at least one guard electrode; a shielding electrode interposed between the at least one guard electrode and the at least one measurement electrode, the shielding electrode being electrically connected to a second electrical source independent from the first electrical source, and the guard electrode being electrically connected to a third electrical source independent of the first and second electrical sources; at least one return electrode; insulators positioned between (i) the measurement electrode and the shielding electrode, (ii) the shielding electrode and the guard electrode and (iii) the measurement electrode, the guard electrode and the return electrode; and a processor configured to adjust at least one of the first electrical source and the second electrical source to minimize a current flow through the shielding electrode.

Abstract: A module for use as a subsea electronic module of a subsea well, comprises an input (7) for receiving signals from a sensor arrangement which senses at least one parameter of a well, the module including a plurality of separate, different electronic circuits (9), each of which is selectable to be in communication with said input and each of which is adapted to co-operate with a respective, different form of such a sensor arrangement.

Abstract: Disclosed is an apparatus for estimating a property of an earth formation penetrated by a borehole. The apparatus includes a carrier configured to be conveyed through the borehole and having a first transmitter electrode configured to inject electrical current into the formation and a first measurement electrode configured to receive electrical current for measurement due to the current injection in order to estimate the property of the earth formation. A controller is configured to determine a phase difference between injected electrical current and received electrical current. A first bucker amplifier is coupled to the first measurement electrode and configured to apply a voltage to the first measurement electrode based on the determined phase difference in order for a phase of current received by the first measurement electrode to be substantially in phase with the current injected by the first transmitter electrode.

Abstract: A method used in electrical investigation of geological formations surrounding a borehole comprising: determining S1 a grid of iso-parameter lines GR in a two-dimensional plane, the parameter being an electrical parameter characterizing the geological formation, injecting in a localized manner a survey current IS into a selected zone SZ of the geological formations GF surrounding the borehole BH, and measuring S2 a measured value of a quantity characterizing the electrical parameter of the selected zone based on the survey current, and interpolating S3 an interpolated electrical parameter value of the selected zone SZ based on the measured value and the grid of iso-parameter lines GR.

Abstract: A microresistivity logging tool includes a dual function electrode deployed between a guard electrode and a return electrode. A drive circuit enables the electrical potential of the dual function electrode to be independently controlled so as to control a depth of investigation of a microresistivity measurement. The depth of investigation tends to increase with increasing electrical potential of the dual function electrode.

Abstract: An apparatus and method for performing high transverse resolution voltage measurements in downhole logging tools utilized to determine the resistivity of an adjacent portion of a borehole wall. Two current electrodes 508 and 509 are energized by an excitation source to create an oscillatory electric field in a borehole wall. The voltage drop from each voltage electrode in a row of laterally spaced voltage electrodes 604 is measured relative to a shared voltage electrode 606 longitudinally spaced from the row of electrodes. The differential voltage is used in combination with a measured current flow to determine a resistivity value for the borehole. A second row of laterally spaced voltage electrodes 608 having electrodes laterally offset from the electrodes of the first row is included to provide high transverse resolution. A common mode voltage at the shared voltage electrodes is measured and utilized to minimize the resistivity measurement error.

Abstract: In some embodiments, apparatus useful for determining at least one dimension of at least one geological feature of an earthen formation from a subterranean well bore includes at least two electric current transmitting electrodes and at least two sensing electrodes disposed in the well bore. The electric current transmitting electrodes are configured to create an electric field and the sensing electrodes are configured to detect perturbations in the electric field created by at least one target object.

Abstract: An apparatus and method for minimizing the effects of a common mode voltage signal in downhole logging tools utilized to determine the resistivity of an adjacent portion of a borehole wall. Two current electrodes are energized by an excitation source to create an oscillatory electric field in a borehole wall. A voltage drop across a segment of the borehole wall is measured by two voltage electrodes, and the differential voltage is used in combination with a measured current flow to determine a resistivity value for the borehole wall. A common mode voltage in front of the two voltage electrodes is measured and minimized by controlling the excitation source, thereby reducing the resistivity measurement error.

Abstract: A microresistivity logging tool includes a shield electrode deployed between a guard electrode and a return electrode. A measuring electrode is deployed in and electrically isolated from the guard electrode and first and second potential electrodes are deployed in and electrically isolated from the shield electrode. The tool further includes at least one switch configured to switch the tool between distinct first and second microresistivity measurement modes. The first measurement mode is configured for making microresistivity measurements in conductive (water based) drilling fluid and the second measurement mode is configured for making microresistivity measurements in non-conductive (oil based) drilling fluid, thereby enabling the tool to be utilized in either type of drilling fluid.

Abstract: A method of servicing a wellbore comprising placing an oil-based wellbore servicing fluid comprising an electrical conductivity enhancer into the wellbore and logging the wellbore by resistivity imaging. A method of servicing a wellbore comprising introducing an oil-based drilling fluid to a wellbore, identifying a subsection of the wellbore for imaging, introducing to the subsection of the wellbore a oil-based wellbore servicing fluid comprising a carbon nanotube wherein the servicing fluid comprising the electrical conductivity enhancer mixes with the oil-based drilling fluid; and imaging the subsection of the wellbore.

Abstract: Oil-based mud imaging systems and methods having leakage current compensation. In some embodiments, disclosed logging systems include a logging tool in communication with surface computing facilities. The logging tool is provided with a sensor array having at least two voltage electrodes positioned between at least two current electrodes that create an electric field in a borehole wall, and is further provided with electronics coupled to the current electrodes to determine a differential voltage between the voltage electrodes in response to different current frequencies from the current electrodes. From the voltage measurements at different frequencies, the computing facilities determine borehole wall resistivity as a function of depth and azimuth, and may display the resistivity as a borehole wall image.

Abstract: An apparatus and method for reducing an electric current leakage in a logging tool, particularly relating to reducing electric current leakage by altering a phase difference between a biasing element and an electric current produced by a first power source. The apparatus may include one or more measure electrodes for imparting electric current into a formation, a current meter, at least one current return electrode, a controller, and a biasing element. The method includes adjusting a phase angle difference between the current leaving the measure electrode and a biasing signal applied to the biasing element from a second power source to reduce the current leakage of the apparatus.

Abstract: A method for correcting data from a sensor electrode in a sensor includes determining a potential difference (V) between the sensor electrode and another sensor electrode; from the potential difference (V), determining a by-pass current (Ic) between the sensor electrode and the another sensor electrode; and from the by-pass current (Ic) and a measured current (I) from the sensor electrode, determining a corrected current (J) for the sensor electrode; wherein determining a potential (V1) for the sensor electrode comprises multiplying an intrinsic impedance (Zi1) by the measured current (I). A computer program product and other embodiments are provided.