Abstract: A plurality of energy-generator pods, and methods of use, are provided along a rotatable tubular string extending downhole from surface into a wellbore. In embodiments, rotation of the tubular acts as a rotor of the pod and an outer component about the tubular, capable of relative rotation thereabout, forms the stator. The pod can also be equipped with bi-directional wireless electronic data communication including communication uphole to surface from sensors downhole, pod-to-pod, and down-hole communication to downhole tools. Pods can be fit to centralizers already employed for rotary tubular strings, the centralizer portion engaging the wellbore and remaining stationary relative to the rotating centralized tubular.

Abstract: A down-hole tool includes at least one wall. The at least one wall may include a plurality of joined substantially parallel layers of material, a plurality of pockets defined within the at least one wall, each pocket of the plurality of pockets including a plurality of openings formed in consecutive layers of the plurality of joined substantially parallel layers of material, and a plurality of recesses defined within the at least one wall and between layers of the plurality of joined substantially parallel layers of material, the plurality of recesses defining at least one conduit. The down-hole tool also includes at least one electronic component disposed within a pocket of the plurality of pockets and at least one electrical connection disposed within the at least one conduit.

Abstract: Methods, apparatus, systems, and articles of manufacture are disclosed to measure a formation feature. An example apparatus includes a pre-processor to compare a first measurement obtained from a first sensor included in a logging tool at a first depth at a first time and a second measurement obtained from a second sensor included in the logging tool at the first depth at a second time. The example apparatus also include a semblance calculator to: calculate a correction factor based on a difference between the first measurement and the second measurement; and calculate a third measurement based on the correction factor and a fourth measurement obtained from the first sensor at a second depth at the second time. The example apparatus also includes a report generator to generate a report including the third measurement.

Abstract: A method and system for a rotary steerable system (RSS). The method may comprise performing a tool position calculation from the one or more measurements and creating one or more event flags based at least in part on a location of the RSS in a formation, wherein the one or more event flags are created by an information handling system disposed on a bottom hole assembly. The method may also comprise selecting an algorithm for the tool position calculation based on the one or more event flags. The system may comprise one or more sensors configured to take one or more measurements and an information handling system disposed on a bottom hole assembly.

Abstract: A resistivity-measuring sensor disposable within a drillstring includes a sensor body having a longitudinal axis, wherein the sensor body is separable from and disposable in the drillstring at a radially offset distance from the longitudinal axis of the drillstring. The sensor further includes a transmitting antenna disposed along a length of the sensor body, a receiving antenna disposed along a length of the sensor body, and an electronics section contained within the sensor body for generating and receiving signals to and from the transmitting and receiving antennas.

Abstract: A resistivity measurement while drilling (MWD) device, including: a transmitting module arranged on an outer surface of a drill collar, for generating an induced current between the drill collar and surrounding formation by inductive coupling; a receiving electrode group including at least two electrodes, for receiving a measured current that reaches the electrode from the induced current through corresponding formation, two electrodes in the receiving electrode group being multiplexing electrodes; a resistivity calculation module configured to be connected to all or a part of the electrodes in the receiving electrode group in a measurement mode of the resistivity MWD device, to calculate the measured current received by a corresponding electrode and obtain resistivity of formation corresponding to the corresponding electrode; and a data transmission module configured to be connected to the multiplexing electrodes in a transmission mode of the resistivity MWD device, for transmitting calculated resistivity to

Abstract: A system for guiding a well comprises a current source, a ground terminal electrically connected to the current source and grounded at the surface of the Earth, a reference wellbore comprising an intermediate casing (IC) that includes an IC electrical discontinuity and is electrically conductive between that the IC discontinuity and the IC bottom hole, a reference conductor electrically connected to the current source, a tubular that includes a tubular string electrical discontinuity (TSED), is electrically conductive between the TSED and the tubular bottom hole end (TBHE), and is inserted into the reference wellbore through the IC. Electrical connections exist between the tubular, the reference conductor, and the reference wellbore between the TSED and the TBHE, whereby current flowing through the reference conductor produces a magnetic field; magnetic sensors to sense the magnetic field and a guided wellbore is steered in response to the sensed magnetic field.

Abstract: The present disclosure introduces an apparatus for downhole measurement of a formation resistivity. The apparatus includes a probe having a button electrode, a first guard electrode insulated from the button electrode, a second guard electrode insulated from the first guard electrode, and a return electrode positioned external to the second guard electrode. The apparatus also includes an electrical source for setting a voltage drop between the second guard electrode and the return electrode, a first impedance (RBOG) electrically coupled between the button electrode and the second guard electrode, and a second impedance (RIGOG) electrically coupled between the first guard electrode and the second guard electrode.

Abstract: Various resistivity logging tools, systems, and methods are disclosed. At least some system embodiments include a logging tool and at least one processor. The logging tool provides transmitter-receiver coupling measurements that include at least direct coupling along the longitudinal tool axis (Czz), direct coupling along the perpendicular axis (Cxx or Cyy), and cross coupling along the longitudinal and perpendicular axes (Cxz, Cyz, Czx, or Czy). The processor performs a multi-step inversion of said transmitter-receiver coupling measurements to obtain values for model parameters. Based at least in part on the model parameters, the processor determines borehole corrections for the transmitter-receiver coupling measurements and may further provide one or more logs derived from the borehole corrected transmitter-receiver coupling measurements.

Abstract: Methods and tools for detecting casing position downhole is presented. The method utilizes electromagnetic (EM) tools with tilted antenna systems to detect casing position. Sometimes titled antenna designs also increase EM tools' sensitivity to formation parameters, which can lead to false signals for casing detection. In addition, it is very difficult to distinguish measured signals between a casing source and a formation source. The methods presented help to distinguish between the two sources more clearly. The methods and tools presented also help to minimize those environmental effects, as well as enhance the signals from a surrounding conductive casing. The methods herein provide ideas of EM tool's design to precisely determine casing position within a certain distance to casing position.

Abstract: An insert to convert a conventional rotary drill bit to a rotary steerable bit for a rotational directional drilling system. The insert comprises a cylindrical body adapted to be arranged within an intermediate space of the drill bit for receiving drilling fluid from a drill string and selectively directing the drilling fluid to nozzles of the drill bit. The insert may be rotatable and connected to a geostationary platform. Alternatively, the insert may be fixated in the drill bit, combined with a flow diverter connected to a geostationary platform. The insert is suitable to be introduced in the drill bit at a drilling location, including remote locations and off-shore rigs.

Abstract: Methods and tools for detecting casing position downhole is presented. The method utilizes electromagnetic (EM) tools with tilted antenna systems to detect casing position. Sometimes titled antenna designs also increase EM tools' sensitivity to formation parameters, which can lead to false signals for casing detection. In addition, it is very difficult to distinguish measured signals between a casing source and a formation source. The methods presented help to distinguish between the two sources more clearly. The methods and tools presented also help to minimize those environmental effects, as well as enhance the signals from a surrounding conductive casing. The methods herein provide ideas of EM tool's design to precisely determine casing position within a certain distance to casing position.

Abstract: Systems and methods are provided to obtain multiple resistivity measurements using a resistivity tool eccentered and rotating in a wellbore, which may be used to ascertain information relating to a drilling fluid in the wellbore. One such system includes a resistivity tool and data processing circuitry. The resistivity tool may become eccentered in a wellbore filled with drilling mud at least when the wellbore is at least partially deviated. The resistivity tool may also rotate within the wellbore and to obtain at least two resistivity measurements at different corresponding angles of rotation within the wellbore. The data processing circuitry may determine a mud phase angle by comparing the resistivity measurements obtained by the resistivity tool.

Abstract: A cutting element for an earth-boring drilling tool comprises a cutting body having a cutting surface thereon, and a sensor coupled with the cutting surface, the sensor configured to determine resistivity of a contacting formation. An earth-boring drilling tool comprises a bit body and an instrumented cutting element coupled with the bit body. The cutting element includes a cutting body having a cutting surface thereon, and at least one sensor located proximate the cutting surface. The at least one sensor is oriented and configured to determine resistivity of a contacting formation. A method of determining resistivity of a subterranean formation during a drilling operation comprises energizing a sensor of an instrumented cutting element of a drill bit, sensing a return signal flowing on or through the subterranean formation through the instrumented cutting element, and determining a resistivity of the subterranean formation based, at least in part, on the return signal.

Abstract: A system and apparatus for configuring a well logging assembly having an elongate sub with a bore therethrough, a leading end connection and a trailing end connection, a plurality of sets of recesses in an exterior wall of the sub to receive a plurality of sets of inserts, each having a threaded exterior surface, a plurality of internally threaded retainer rings, and a plurality of well logging devices securable to the exterior wall of the sub using the retainer rings to threadably engage the inserts received in the recesses. The system enables convenient configuration and reconfiguration of the well logging assembly by enabling convenient securing of a first well logging instrument to the sub at a variety of spacings from a second well logging instrument to provide a variety of depths of investigation into a geologic formation penetrated by a drill string containing the well logging assembly.

Abstract: An apparatus and method of performing a wellbore operation. The apparatus includes a drill bit that has a cavity at an end thereof and a communication device placed in the cavity. The communication device includes a first section and a second section. An outer dimension of the second section is greater than an outer dimension of the first section. The second section includes a conduit configured to allow passage of a conductor from the drill bit to a location outside the drill bit so as to provide a direct connection of the conductor from the drill bit to an element outside the drill bit.

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: 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: Systems and methods are provided to obtain multiple resistivity measurements using a resistivity tool eccentered and rotating in a wellbore, which may be used to ascertain information relating to a drilling fluid in the wellbore. One such system includes a resistivity tool and data processing circuitry. The resistivity tool may become eccentered in a wellbore filled with drilling mud at least when the wellbore is at least partially deviated. The resistivity tool may also rotate within the wellbore and to obtain at least two resistivity measurements at different corresponding angles of rotation within the wellbore. The data processing circuitry may determine a mud phase angle by comparing the resistivity measurements obtained by the resistivity tool.

Abstract: A drilling system includes integral drill bit body and logging while drilling tool body portions. There are no threads between the drill bit and the LWD tool. In one exemplary embodiment the drilling system includes a unitary tool body, i.e., a tool body formed from a single work piece. In another exemplary embodiment the drill bit body portion is welded to the LWD tool body portion. At least one LWD sensor is deployed in the drill bit. The drilling system enables multiple LWD sensors to be deployed in and near the bit (e.g., on both the side and bottom faces of the bit). The absence a threaded connection facilitates the placement of electrical connectors, LWD sensors, and electronic control circuitry at the bit.

Abstract: The present disclosure relates to a method to determine a characteristic of a subsurface formation using a downhole logging tool. A downhole logging tool having the ability to make substantially concurrent disparate measurements on the subsurface formation is provided and substantially concurrent disparate measurements on the formation using the downhole logging tool are made. Those measurements are used to solve a system of equations simultaneously and the solution to the system of equations is used to determine the characteristic of the subsurface formation.

Abstract: A drill bit assembly for measuring reservoir formation properties comprises a bit head and a pin body, and an electrically insulated gap joint between two conductive parts of the drill bit assembly. The bit head has a cutting end and an opposite connecting end with an engagement section. The pin body comprises a connecting end with an engagement section. The pin connecting end is connected to the bit head connecting end such that the engagement sections overlap. The electrically insulating gap joint can fill a gap between the bit head and pin body engagement sections such that the bit head and pin body are mechanically connected together at the connecting ends but electrically separated. Alternatively or additionally, the pin body can have two pieces which are separated by an electrically insulating gap joint.

Abstract: An instrument for measuring a property of a subsurface material, the instrument including: a magnetic material surrounding a volume in at least two dimensions; and a receiver adapted for receiving energy related to the property of the subsurface material; wherein the receiver is disposed at an exterior surface of the magnetic material.

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: Methods for making calibrated microresistivity logging measurements in nonconductive drilling fluid are disclosed. A calibrated measurement parameter (e.g., a calibrated electrical impedance or a calibrated potential difference) is obtained and further utilized to compute a formation resistivity. The methods tend to be particularly well suited for drilling applications in which the borehole environment is highly resistive (i.e., boreholes in which both the drilling fluid and the formation have a high resistivity).

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: A system for automating service operations at a well includes a service rig having at least one input device, an engine connected to an engine electronic control unit having a engine controller area network, a plurality of crown sheeves, a cable, an output device, a communication infrastructure, and at least one of a computer and an operator station; at least one remote server in electronic communication with the communication infrastructure; and a web portal in electronic communication with the at least one remote server.

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 method of logging an invaded geological formation comprises the steps of: (i) operating plural receivers in order to receive signals generated by one or more transmitters and thereby create logs of overlapping lengths of a bore formed in the said geological formation, the respective said receivers logging distinct depths of penetration, as previously defined, of the geological formation measured with respect to the bore; (ii) recording the resultant values in a two-dimensional plot one of whose axes represents the respective depth of penetration of the said formation to which each said log corresponds; (iii) establishing whether the resulting plot appears to approach an asymptote; and if so (iv) determining the value of the asymptote.

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.

Abstract: A microresistivity logging tool includes a measuring electrode deployed in and electrically isolated from a guard electrode. The measuring electrode is radially recessed with respect to at least a portion of the guard electrode. The raised portion of the guard electrode preferably extends radially outward from the tool body such that it contacts the borehole wall during drilling. A return electrode is spaced and electrically insulated from the guard electrode. Tools in accordance with the present invention enable good current focusing to be achieved while at the same time providing protection for the measuring electrode.

Abstract: A logging sonde includes a tube defining a sealed chamber inside. An isolation layer is disposed on an exterior of the tube. At least one sensor is disposed on an exterior of the isolation layer. The sensor includes a lead in passing through a wall of the tube. An elastomer jacket is disposed on an exterior of the sensor and the isolation layer. A method for making a sonde includes affixing an electrically insulating isolator to an exterior of a tube. An hydraulic seal layer is affixed over an exterior of the isolator. A sensor is affixed over the exterior of the seal layer. An electrical connection is made from the sensor to an interior of the tube through the hydraulic seal layer and through the isolator. An elastomer jacket is applied over the exterior of at least part of the sensor and the exterior of the seal layer.

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 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 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: A drilling system includes integral drill bit body and logging while drilling tool body portions. There are no threads between the drill bit and the LWD tool. In one exemplary embodiment the drilling system includes a unitary tool body, i.e., a tool body formed from a single work piece. In another exemplary embodiment the drill bit body portion is welded to the LWD tool body portion. At least one LWD sensor is deployed in the drill bit. The drilling system enables multiple LWD sensors to be deployed in and near the bit (e.g., on both the side and bottom faces of the bit). The absence a threaded connection facilitates the placement of electrical connectors, LWD sensors, and electronic control circuitry at the bit.

Abstract: An integrated electrode resistivity and EM telemetry tool and obtaining both formation resistivity and telemetry data from the integrated tool. An integrated electrode resistivity and EM telemetry tool having a drill collar including a first portion and a second portion separated by an insulated gap and telemetry cartridge carrying telemetry circuitry including a voltage source generating a voltage drop across the insulated gap and an axial current on a drill string that returns through an earthen formation includes an insulated measure electrode connected to the first portion, and resistivity measurement circuitry functionally connected to the measure electrode and the telemetry circuitry.

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: Transducer apparatus for subsurface use. A tubular configured for subsurface disposal is equipped with a cylindrical transducer module formed of a non-conductive material. The module is mounted to surround a section of the tubular and includes a transducer element disposed thereon such that only a surface of the element is exposed along the exterior of the module body. The transducer element is linked to a lead routed through the cylindrical body to exit near the inner bore of the body. The ends of the cylindrical body are covered with a material to form a hydraulic seal. A method for constructing the transducer apparatus.

Abstract: This invention is directed to a downhole method and apparatus for simultaneously determining the horizontal resistivity, vertical resistivity, and relative dip angle for anisotropic earth formations. The present invention accomplishes this objective by using an antenna configuration in which a transmitter antenna and a receiver antenna are oriented in non-parallel planes such that the vertical resistivity and the relative dip angle are decoupled. Preferably, either the transmitter or the receiver is mounted in a conventional orientation in a first plane that is normal to the tool axis, and the other antenna is mounted in a second plane that is not parallel to the first plane. This invention also relates to a method and apparatus for steering a downhole tool during a drilling operation in order to maintain the borehole within a desired earth formation.

Abstract: A resistivity sub including a resistivity sensor forms part of a bottom hole drilling assembly. The sensor is maintained at a substantially fixed offset from the wall of a borehole during drilling operations by, for example, a stabilizer. In WBM, galvanic sensors may be used, with or without commonly used focusing methods, for obtaining a resistivity image of the borehole wall. In OBM, capacitive coupling may be used. The apparatus is capable of using other types of sensors, such as induction, MPR, shielded dipole, quadrupole, and GPR sensors. 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. 37 CFR 1.72(b).

Abstract: A method and apparatus for obtaining a resistivity measurement of an earth formation surrounding a borehole in an MWD device uses the drillbit and the adjacent portion of the drill collar as a focusing electrode for focusing the measure current from a measure electrode on the face or side of the drillbit. This provides the ability to see ahead of and azimuthally around the drillbit.

Abstract: An unfocused resistivity imaging device horizontal and vertical currents conveyed into the borehole. Pad mounted electrodes are used to make voltage measurements in orthogonal directions. The voltage measurements are then rotated to give principal resistivity measurements in an anisotropic formation with dipping beds.

Abstract: A device, method and system for measuring characteristics of a geologic formation using a floating reference signal having a mud chamber, an electrode disposed within the mud chamber, and an electrically conductive plate disposed within the mud chamber, the plate separated from the electrode. An alternating current source is provided on the electrode, whereby an electric field is be maintained between the electrode and the conductive plate. An opening in the mud chamber allows drilling fluids to pass there through.

Abstract: Logging-while-drilling apparatus and methodologies for measuring streaming potential in an earth formation are provided. The apparatus and methodologies can be utilized to find information relevant to the drilling operations. In particular, since the streaming potential measurement relates directly to fluid flow, the streaming potential measurements can be used to track flow of fluids in the formation. In turn, this information may be used to find information relevant to the drilling operations, such as under-balanced drilling conditions, abnormal formation pressures, open fractures, the permeability of the formation, and formation pressure.

Abstract: A method for correcting data from at least one sensor electrode in a sensor includes determining a potential difference (V) between two electrodes; from the potential difference (V), determining a by-pass current (Ic) for the at least one sensor electrode; and from the by-pass current (Ic) and a measured current (I), determining a corrected current (J) for the at least one sensor electrode. A computer program product and other embodiments are provided.

Abstract: A downhole tool for formation logging includes a tool body configured to move in a borehole; and at least one sensor module mounted in at least one mounting location on the tool body, wherein the at least one sensor module is interchangeable with other sensor modules that make different measurements. A downhole tool may further comprise a measurement system disposed in the tool body, wherein the measurement system is operatively coupled to the at least one sensor module.

Abstract: An azimuthally sensitive electromagnetic measurement tool is provided. The tool may be suitable, for example, to measure azimuthal variations of electrical properties of a subterranean formation. The tool includes a transmitter disposed to transmit electromagnetic energy into a subterranean formation and a longitudinally spaced receiver. At least one of the transmitter and the receiver includes a sector antenna. The sector antenna includes an exposed length of antenna wire that forms an arc about a portion of a circumference of the tool body. In one exemplary embodiment, the receiver includes first and second sector antennae, which, in combination, subtend a circular angle of about 360 degrees about the circumference of the tool body without substantially overlapping one another.

Abstract: A resistivity sub including a resistivity sensor forms part of a bottom hole drilling assembly. The sensor is maintained at a substantially fixed offset from the wall of a borehole during drilling operations by, for example, a stabilizer. In WBM, galvanic sensors may be used, with or without commonly used focusing methods, for obtaining a resistivity image of the borehole wall. In OBM, capacitive coupling may be used. The apparatus is capable of using other types of sensors, such as induction, MPR, shielded dipole, quadrupole, and GPR sensors.