Abstract: Downhole monitoring systems are described. The systems include a downhole string disposed in a borehole, the string having a downhole tool and the borehole has fluid therein. A sacrificial electrical sensor element is arranged in or on the string. The sacrificial electrical sensor element includes magnetic material at least partially exposed to the fluid and at least one coil arranged in magnetic communication with the magnetic material. A controller is configured to provide an electrical current into the coil, measure an electrical property of the coil that is based on the magnetic material in magnetic communication with the coil, and determine a wear state of the downhole tool based on the measured electrical property.

Abstract: Disclosed is a method and device for determining characteristics of metallic casing and casing attenuation, the method includes the following steps: obtaining the ratio of first magnetic field with metallic casing and without metallic casing at DC mode; obtaining magnetic related parameter of the metallic casing; obtaining magnetic permeability of metallic casing; obtaining the ratio of second magnetic field with metallic casing and without metallic casing at AC mode; obtaining electrical related parameter of the metal casing through the ratio of the second magnetic field and the magnetic related parameter of the metal casing; obtaining electrical conductivity of metallic casing through the electrical related parameter; obtaining casing attenuation of metallic casing through the magnetic related parameter and the electrical related parameter. The beneficial effect of this disclosure is: this method can obtain characteristics and casing attenuation of metallic casing without measuring impedance.

Abstract: A method includes providing a Bottom Hole Assembly (BHA) in a wellbore. The BHA includes a rotary steerable system and a downhole attitude correction and control system. The downhole correction and control system includes a first sensor set, the sensors of the first sensor set positioned near ferromagnetic components of a drill string and a second sensor set, the sensors of the second sensor set positioned further from the ferromagnetic components of the drill string than the sensors of the first sensor set. Corrupted data from the first sensor set and reference data from the second sensor set is obtained, the corrupted data including cross-axis magnetometer and accelerometer measurements. The method additionally includes correcting the corrupted sensor data to form corrected sensor measurements and calculating an estimated azimuth from the corrected sensor measurements. The method further includes steering the rotary steerable system based on the estimated azimuth.

Abstract: A method, system, and apparatus for determining the location of a tool traveling down a wellbore by measuring a first borehole magnetic anomaly with respect to time at two known locations on a tool, comparing the time difference between the two measurements, then calculating the velocity of the tool based on the comparison and then further calculating the distance traveled by the tool in the wellbore based on the velocity calculation.

Abstract: A method, system, and apparatus for determining the location of a tool traveling down a wellbore by measuring a first borehole magnetic anomaly with respect to time at two known locations on a tool, comparing the time difference between the two measurements, then calculating the velocity of the tool based on the comparison and then further calculating the distance traveled by the tool in the wellbore based on the velocity calculation.

Abstract: A method includes generating a ranging model of a drilling wellbore to be drilled and generating a predicted signal along measured depths of the drilling wellbore based on the ranging model. The method includes performing the following operations until the drilling wellbore has been drilled to a defined depth. The following operations include drilling, with a drill string, the drilling wellbore to an increment of the defined depth and detecting, by a sensor positioned on the drill string, an electromagnetic field emanating from a target wellbore. The following operations include determining ranging measurements to the target wellbore at the increment based on the electromagnetic field and calibrating the predicted signal based on the ranging measurements. The following operations include determining ranging accuracy for all deeper depths in the wellbore and making drilling decisions or adjusting drilling operations based on the predicted ranging accuracy for deeper depths.

Abstract: A method for investigating well integrity, the method including pumping a magnetic fluid into an annulus of the well; magnetizing with a magnet the magnetic fluid while in the annulus of the well; moving a magnetic sensing probe through a casing of the well and recording a magnetic field generated by the magnetic fluid; and processing the recorded magnetic field to determine a distribution of magnetic particles into the magnetic fluid in the annulus.

Abstract: A method can include measuring temperature along a relief wellbore, thereby detecting a temperature anomaly in an earth formation penetrated by the relief wellbore, and determining a location of an influx into a target wellbore, based on the temperature anomaly detecting. A thermal anomaly ranging system for use with a subterranean well can include a temperature sensor in a relief wellbore that penetrates an earth formation, the temperature sensor detecting a temperature anomaly in the formation, and the temperature anomaly being caused by an influx into a target wellbore. Another method can include measuring optical scattering in an optical waveguide positioned in a relief wellbore, thereby detecting a temperature anomaly in an earth formation penetrated by the relief wellbore, and determining a location of an influx into a target wellbore, based on the temperature anomaly detecting.

Abstract: A tracking system for communicating a location of a beacon in order to drill a bore path. The beacon is carried by a drill string in a drilling operation. Above-ground trackers are arranged in a path to define an intended underground bore path. The trackers form a multi-node mesh network in communication with a display unit at a drilling rig. A drilling operator guides the drill string in response to tracking data sent from the tracking system.

Abstract: A method includes deploying an electromagnetic (EM) defect detection tool in a borehole having one or more tubular strings. The method also includes collecting measurements by the EM defect detection tool as a function of measured depth or position. The method also includes using the measurements and a first inversion process to determine a defect in the one or more tubular strings. The first inversion process involves a cost function having a misfit term and having a stabilizing term with nominal model parameters. The method also includes performing an operation in response to the determined defect.

Abstract: In some embodiments, an apparatus and a system, as well as a method and an article, may operate to access rock property measurements taken within shale basins; to transform the rock property measurements into Estimated Ultimate Recovery (EUR) estimates for wells operating within the shale basins, the EUR estimates being further based on values for shale thickness, porosity, and hydrocarbon saturation measured within the shale basins; to generate metrics for ranking drilling locations, the drilling locations including wells for which the EUR estimates were generated; and to provide drilling coordinates to control a drilling instrument for recovering shale basin resources in the drilling locations according to the ranked list. Additional apparatus, systems, and methods are disclosed.

Abstract: Born Scattering Inversion (BSI) systems and methods are disclosed. A BSI system may be incorporated in a well system for accessing natural gas, oil and geothermal reserves in a geologic formation beneath the surface of the Earth. The BSI system may be used to generate a three-dimensional image of a proppant-filled hydraulically-induced fracture in the geologic formation. The BSI system may include computing equipment and sensors for measuring electromagnetic fields in the vicinity of the fracture before and after the fracture is generated, adjusting the parameters of a first Born approximation model of a scattered component of the surface electromagnetic fields using the measured electromagnetic fields, and generating the image of the proppant-filled fracture using the adjusted parameters.

Abstract: A surface excitation ranging method includes installing a customized grounding arrangement for a power supply located at earth's surface, wherein the customized grounding arrangement fulfills an impedance criteria or ranging performance criteria. The method also includes conveying an electrical current output from the power supply along a target well with a metal casing. The method also includes sensing electromagnetic (EM) fields emitted from the target well due to the electrical current. The method also includes using distance or direction information obtained from the sensed EM fields to guide drilling of a new well relative to the target well.

Abstract: Planning and real time optimization of one or more modules of a downhole tool provide efficient and cost-effective deployment of a measurement system, for example, for a ranging tool. Considerations of the environment and type of operation may be considered prior to the deployment of a downhole tool such that the downhole tool comprises modules that may be optimized. Certain modules may be activated for specific operations without having to extract the downhole tool as all modules necessary to perform the specific tasks for a given operation are included prior to deployment of the downhole tool. The one or more modules may be optimized in real time based, for example, on received measurements or previous survey results. The modularity of the downhole tool allows for flexibility in fine tuning the tool according to a varying formation environment and other parameters.

Abstract: Systems and methods for utilizing diverse excitation sources in single well electromagnetic ranging. A method may include disposing an electromagnetic ranging tool in a wellbore, wherein the electromagnetic ranging tool may comprise one or more receivers, a coil source and an electrode source; performing a measurement with the one or more receivers of at least one component of a coil-induced magnetic field from the target wellbore to provide a coil measurement, wherein the coil-induced magnetic field may be induced by the coil source; performing a measurement with the one or more receivers of at least component of an electrode-induced electromagnetic field to provide an electrode measurement, wherein the electrode-induced electromagnetic field may be induced by the electrode source; and calculating at least one ranging parameter using, at least in part, the coil measurement and the electrode measurement.

Abstract: A method to produce a magnet arrangement, the method having steps of selecting a depth of investigation to be achieved by a downhole tool, identifying a desired magnetic field strength at the depth of investigation, producing a set of magnets to be incorporated into the downhole tool, sorting the set of magnets based on a quality of each of the magnets and optimizing the set of magnets such that the quality of each of the magnets results, when arranged, in the desired magnetic field strength at the depth of investigation and wherein the optimizing minimizes a cost function of the set of magnets produced.

Abstract: Contrast agents and methods for use in geological applications are provided. Contrast agents can be a nanopolymorph material, such as titania nanotubes, and have a low-frequency dielectric permittivity. Methods of identifying one or more subterranean features during geological exploration are provided. Methods of identifying a ganglion of bypassed oil are provided. Methods of illuminating subterranean fractures in hydraulic fracturing are provided.

Abstract: Production of perforated two-dimensional materials with holes of a desired size range, a narrow size distribution, and a high and uniform density remains a challenge, at least partially, due to physical and chemical inconsistencies from sheet-to-sheet of the two-dimensional material and surface contamination. This disclosure describes methods for monitoring and adjusting perforation or healing conditions in real-time to address inter- and intra-sheet variability. In situ or substantially simultaneous feedback on defect production or healing may be provided either locally or globally on a graphene or other two-dimensional sheet. The feedback data can be used to adjust perforation or healing parameters, such as the total dose or efficacy of the perforating radiation, to achieve the desired defect state.

Abstract: Disclosed embodiments include methods and apparatus for ranging techniques to detect and determine a relative distance and azimuthal direction of nearby target well conductors such as pipes, well casing, etc., from within a borehole of a drilling well. A nearby casing string of a target well can be detected by transmitting an electromagnetic signal from an excitation source located along the target well and measuring a response signal with an antenna on a downhole logging tool in the drilling well. Several different excitation sources for various target wells are utilized to distinguish nearby conductor signals from formation signals. Joint]inversion algorithms are utilized to identify multi]well locations on the basis of measured signal responses from the different excitations sources. The joint]inversions may be implemented in real]time or during post]processing, and used in applications such as SAGD, anti]collision, and relief well development.

Abstract: Methods for drilling a second well in a spatial relationship to a first well include positioning a magnetic field source in a first well or borehole and deploying at least two magnetometers in a second well or borehole. The magnetometers are separated by a known distance and each measure the magnetic field created by the magnetic field source that is located in the first borehole. The magnetic field measurements are used to calculate the locations of the two magnetometers with respect to the magnetic field source. The two locations define the axis of the second borehole with respect to the magnetic field source in the first borehole.

Abstract: Various systems and methods for implementing and using a downhole all-optical magnetometer include downhole all-optical magnetometer sensor, including optical receiving ports that receive light pulses, a depolarizer that depolarizes received light pulses, and a polarizer that polarizes depolarized light pulses from the depolarizer. The sensor further includes a vapor-filled cell through which polarized light pulses from the polarizer are directed, wherein interactions between vapor and a magnetic field within the vapor-filled cell alter at least some of the polarized light pulses, and an optical transmitting port that directs altered light pulses from the vapor-filled cell out of the sensor.

Abstract: A series of electromagnetic field strength measurements is acquired from a sensor at multiple depths in a first well, responsive to an electromagnetic field originating at a second well, via at least one of a direct transmission and a backscatter transmission. A drilling phase associated with drilling operations conducted in the first well is determined. A sensor separation depth associated with the drilling phase is selected. An approximate range between the first well and the second well is calculated, based on the series of electromagnetic field strength measurements and the sensor separation depth.

Abstract: A dynamic real time transmission line monitor, a dynamic real time transmission line monitoring system, and a method of dynamic real time transmission line monitoring. A dynamic real time transmission line monitor includes a housing installable on a transmission line, the housing including a base portion, and a cover portion coupled to the base portion and defining a cavity of the housing together with the base portion; a sensor configured to sense in real time at least one of a temperature, a position, a current, an acceleration, a vibration, a tilt, a roll, or a distance to a nearest object; and an antenna in the cavity of the housing and configured to transmit a signal including information sensed by the sensor away from the monitor in real time.

Abstract: A well ranging apparatus, systems, and methods which operate to detect and determine a relative distance and/or azimuthal direction of nearby target well conductors such as pipes, well casing, etc., from within a borehole of a drilling well. An electromagnetic signal receiver is rotated in a first borehole. During the rotating, an electromagnetic ranging signal is received at the electromagnetic signal receiver. The electromagnetic ranging signal originates from an electromagnetic source in the first borehole or a second borehole. A null in an Earth electromagnetic signal spectrum associated with a signal induced by the rotating within a magnetic field of the Earth is determined. The electromagnetic source to is set to operate at an excitation frequency that is selected based, at least in part, on the determined null.

Abstract: The present disclosure relates to an electrowetting display device and a manufacturing method for the same, using a UV light reactive fluorosurfactant layer. The UV light reactive fluorosurfactant layer can include a UV-cured fluorine based material positioned above a cured UV reactive material. In an embodiment, the electrowetting display device can also include a substrate with a layer of pixel electrodes formed over the substrate, and partition walls formed over at least a portion of the layer of pixel electrodes. In one embodiment, the UV light reactive fluorosurfactant layer can be formed between the partition walls and above an inter-layer insulation film. In another embodiment, the UV light reactive fluorosurfactant layer can be formed between the partition walls and above the layer of pixel electrodes. The electrowetting display can also include a water repellent layer formed over the UV light reactive fluorosurfactant layer.

Abstract: A downhole magnetic ranging tool includes first and second axially spaced magnetic sources deployed in a downhole tool body. The first and second magnetic sources have magnetic moments that axially opposed one another. A magnetic field sensor is deployed axially between the first and second magnetic sources. The tool may be utilized, for example, in subterranean well twinning, well intercept, and well avoidance operations to obtain a separation distance and dip angle between a drilling well and a target well.

Abstract: Embodiments of a multi-axial antenna system and system for measuring subsurface formations are generally described herein. Other embodiments may be described and claimed. In some embodiments, the multi-axial antenna system comprising at least two co-located coils wound around a torroidal-shaped bobbin. Each coil generates a magnetic field in a mutually orthogonal direction. Signals provided to the coils may be adjusted to simulate a tilted-coil antenna system.

Abstract: An improved system and method for ranging while drilling, in effect, induces a dynamic hot spot on the casing of a nearby well. The induced hot spot acts as a magnetic source that can be reliably detected from within the drillstring and in such a manner as to infer the relative position and orientation of the casing to the drillstring. At least some disclosed method embodiments employ one or more rotating magnets in the drillstring, an array of at least two magnetometers in the drillstring and one or more phase-locked loops that are used to enhance the signal to noise ratio of the magnetic signal scattered off of the casing from the rotating magnetic field. The rotating magnet or magnets may be magnetic dipoles or magnetic multipoles, and may be modulated to enable the use of multiple magnetic field sources.

Abstract: A measuring system for determining the distance to a magnetic alternating field source, with a magnetic sensor arrangement, by means of which a characteristic magnetic alternating field signal of the magnetic alternating field source can be recorded, and an evaluation device connected with the magnetic sensor arrangement and by means of which the characteristic magnetic alternating field signals of the magnetic alternating field source recorded by the magnetic sensor arrangement can be evaluated and converted into the distance between the magnetic alternating field source on the one hand and the magnetic sensor arrangement on the other.

Abstract: An apparatus for determining a distance between a first borehole and a second borehole is provided that in one embodiment includes a rotating magnet on a tool configured for placement in the second borehole for inducing magnetization in a magnetic object in the first borehole, a first coil and a second coil placed radially symmetrically with respect to an axis of the tool, the first coil providing a first signal and second coil providing a second signal responsive to a magnetic flux resulting from the magnetization in the magnetic object in the first borehole, and a controller configured to combine the first signal and the second signal and determining distance between the first borehole and the second borehole using the combined signal.

Abstract: Measuring a parameter characteristic of a formation in an oil well with a device configured to generate a sensing field within a volume of the formation and cause a flow through the volume in the presence of the sensing field. The device also comprises sensors responsive to changes in the volume, which indicate existent amounts of fluid, such as hydrocarbon and water saturations and irreducible hydrocarbon and water saturations. Measurements may be made before the flow affects the measuring volume and after onset of the flow through the measuring volume.

Abstract: The present disclosure relates to a method to determine a volume of clearance surrounding a wellbore. A logging tool is provided. The logging tool may be disposed on a wireline, a drill string, or a wired drill pipe. A formation property is obtained using the logging tool. The formation property may include a voltage, a bulk resistivity, a horizontal resistivity, a vertical resistivity, a porosity, a permeability, a fluid saturation, an NMR relaxation time, a borehole size, a borehole shape, a borehole fluid composition, an MWD parameter, or an LWD parameter. The maximum depth of investigation into the subsurface formation is determined using a model response and a noise level, and the volume of clearance is determined using the determined maximum depth of investigation. The maximum depth of investigation and volume of clearance may be determined even though no boundary layers are detected.

Abstract: An apparatus for estimating at least one parameter of interest of an earth formation includes a first sub and a second sub positioned along the conveyance device. The first sub and the second sub cooperate to generate at least one main component measurement and only the second sub is configured to generate at least one cross-component measurement. A method includes conveying a first sub and a second sub along a wellbore formed in the earth formation using a conveyance device, using the first sub and the second sub to generate at least one main component measurement, and using only the second sub to generate at least one cross-component measurement.

Abstract: Disclosed dielectric logging tools and methods employ three or more receive horn antennas positioned between at least two transmit antennas, which can also be horn antennas. The logging tools can operate in the range between 100 MHz and 10 GHz to provide logs of formation permittivity, formation conductivity, standoff distance, and electrical properties of material in the standoff gap. Logs of water-saturated porosity and/or oil movability can be readily derived. The presence of additional receive antennas offers a significantly extended operating range, additional depths of investigation, increased measurement accuracy, and further offers compensation for tool standoff and mudcake effects. In both wireline and logging while drilling embodiments, at least some disclosed dielectric logging tools employ a set of three axially-spaced receive antennas positioned between pairs of axially-spaced transmit antennas.

Abstract: A method and system is provided for minimizing delays in a magnetic ranging method. Delays are minimized by establishing synchronicity between triggering of a three-axis magnetometer and energization of a solenoid assembly deployed in the borehole being drilled and the first borehole, respectively. Synchronicity enables measuring various components of the alternating magnetic field created by energization of the solenoid assembly by the magnetometer, the moment the solenoid assembly is energized. The recorded components are used for computation of steering data for drilling the second borehole relative to the first borehole. The steering data can be determined at the surface or downhole.

Abstract: A bottom hole assembly configured for a subterranean drilling operation having a drill bit; a downhole tool deployed above the drill bit, at least a portion of the downhole tool free to rotate with respect to the drill bit about a longitudinal axis of the bottom hole assembly a sensor sub deployed axially between the drill bit and the downhole tool, the sensor sub configured to rotate with the drill bit about the longitudinal axis of the bottom hole assembly and free to rotate with respect to the downhole tool about the longitudinal axis and a tri-axial magnetic field sensor deployed in the sensor sub.

Abstract: A seismic sesor for a downhole tool positionable in a wellbore penetrating a subterranean formation. The seismic sensor includes a sensor housing, a bobbin supported in the sensor housing along an axis thereof, at least one coil wound about the bobbin (the coil movably supportable within the sensor housing by at least one spring), at least one magnet positionable about the bobbin to generate a magnetic field with the at least one coil whereby seismic vibrations are detectable, and a filler fluid disposed in the sensor housing to buoy the at least one coil whereby gravitational effects may be neutralized.

Abstract: A generally three-part EM gap sub comprising a first conductive cylinder incorporating a male tapered threaded section, a second conductive cylinder incorporating female tapered threaded section, both axially aligned and threaded into each other is described. One or both tapers incorporate slots whereby non-conductive inserts may be placed before assembly of the cylinders. The inserts are designed to cause the thread roots, crests and sides of the tapered sections of both cylinders to be spatially separated. The cylinders can be significantly torqued, one into the other, while maintaining an annular separation and therefore electrical separation as part of the assembly procedure. The co-joined coaxial cylinders can be placed into an injection moulding machine wherein a high performance thermoplastic is injected into the annular space, thereby forming both an insulative gap (the third part) and a strong joint between the cylinders in the newly created EM gap sub.

Abstract: Downhole tools and techniques acquire information regarding nearby conductors such as pipes, well casing, and conductive formations. At least some method embodiments provide a current flow along a drill string in a borehole. The current flow disperses into the surrounding formation and causes a secondary current flow in the nearby conductor. The magnetic field from the secondary current flow can be detected using one or more azimuthally-sensitive antennas. Direction and distance estimates may be obtainable from the azimuthally-sensitive measurements, and can be used as the basis for steering the drillstring relative to the distant conductor. Possible techniques for providing current flow in the drillstring include imposing a voltage across an insulated gap or using a toroid around the drillstring to induce the current flow.

Abstract: In some embodiments, an apparatus and a system, as well as a method and an article, may operate to acquire a first signal from a first magnetometer at least partially disposed within a Helmholtz coil, to acquire a second signal from a second magnetometer having a sensitivity at least one thousand times less than the first magnetometer, to process the second signal to determine a N drive signal, to drive the Helmholtz coil using the drive signal so as to null an ambient Earth magnetic field surrounding the first magnetometer, and to process the first signal as one of a down hole location signal or a down hole telemetry signal, the location signal to determine a range to a sub-surface object, and the telemetry signal to provide data from down hole drilling operations. Additional apparatus, systems, and methods are disclosed.

Abstract: An angular position sensor can include a magnetic device from which a magnetic field emanates, and multiple magnetometers, whereby each magnetometer senses a varying strength of the magnetic field due to relative rotation between components of a well tool. A method of determining an azimuthal position of a shaft which rotates relative to an outer housing can include securing a selected one of at least one magnetic device and at least one magnetometer to the shaft, securing the other of the magnetic device and the magnetometer to the outer housing, a fluid motor rotating the shaft relative to the outer housing in the well, and the magnetometer sensing a varying strength of a magnetic field emanating from the magnetic device as the shaft rotates relative to the housing.

Abstract: A downhole activation system within a tubular. The system includes an axially movable mover. A first magnet attached to the mover. The first magnet axially movable with the mover. A second magnet separated from the first magnet. The second magnet magnetically repulsed by the first magnet. A biasing device urging the second magnet towards the first magnet; wherein movement of the first magnet via the mover towards the second magnet moves the second magnet in a direction against the biasing device. Also included is a method of activating an activatable member in a downhole tubular.

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 apparatus for steering a drilling assembly within a reservoir of an earth formation is disclosed. The drilling assembly is positioned within the reservoir between a conductive upper layer having a DC magnetic field and a conductive lower layer having a DC magnetic field. A sensor of the drilling assembly measures a magnetic field in the reservoir resulting from the DC magnetic field of the conductive upper layer and the DC magnetic field of the conductive lower layer. A processor uses the measured magnetic field to steer the drilling assembly within the reservoir.

Abstract: An apparatus for estimating a property of an earth formation penetrated by a borehole, the apparatus having: a carrier configured to be conveyed through the borehole; a transmitter disposed at the carrier and configured to transmit electromagnetic energy at a first frequency into the formation; a first antenna disposed at the carrier and configured to receive electromagnetic signals from the formation as a result of the transmitted electromagnetic energy interacting with the formation; and an active filter coupled to the antenna and configured to filter electromagnetic signals received by the antenna to let the electromagnetic signals at the first frequency pass for processing to estimate the property.

Abstract: An electromagnetic method and apparatus for determining the azimuthal orientation of a drill bit instrumentation sub (70), with respect to a borehole bottom drilling assembly (150) includes an electromagnet (152) fastened to the drilling assembly to produce an auxiliary alternating electromagnetic field (162) having an axis (163) that is perpendicular to the borehole axis (160). The direction of the field lines (162) generated by this magnet (152) and the simultaneous measurement of an electromagnetic field (36) generated by current flow in a blowout well casing is measured by electromagnetic field sensors in the drill bit instrument sub (70) to determine the direction to a blowout The direction of the auxiliary field (162) produced by the electromagnet (152) makes it possible to determine the direction to the blowout with reference to the direction of drilling without using an intermediate parameter such as, for example, the direction of gravity.

Abstract: A method for estimating a fracture aperture in a formation penetrated by a well includes obtaining at least one of a vertical resistivity (Rv) and a horizontal resistivity (Rh) of the formation; obtaining a mud resistivity (Rmud) or a matrix resistivity (Rmatrix); and estimating the fracture aperture. The estimating of the fracture aperture may be performed by solving the following two equations: Rv=Vhf·Rm+(1?Vhf)·Rmatrix and 1/Rh=Vhf·1/Rmud+(1?Vhf)·1/Rmatrix, wherein Vhf is the fracture aperture.

Abstract: Methods and apparatus for detecting nearby conductors such as pipes, well casing, etc., from within a borehole. A nearby casing string can be detected by transmitting an electromagnetic signal from a first antenna on a downhole logging tool and measuring a response signal with a second antenna. As the tool rotates, the transmitting and measuring are repeated to determine the azimuthal dependence of the response signal. The azimuthal dependence is analyzed to determine an diagonal component and a cross component. The amplitude of the diagonal component is indicative of distance to the conductive feature. Direction can be determined based on the diagonal component alone or in combination with the cross component. Sinusoidal curve fitting can be employed to improve accuracy of the distance and direction estimates. At least one of the antennas is preferably tilted. Measurement results are presented for parallel tilted and perpendicular tilted antennas.

Abstract: A system and methods for facilitating drilling and/or drilling a well in an orientation with respect to an existing well are provided. Specifically, one method in accordance with present embodiments is directed to producing a magnetic field with a magnetic field source positioned in a non-magnetic region of casing within a first well, wherein the first well is cased with alternating regions of magnetic casing and non-magnetic casing. The method may also include producing at least one output from at least one magnetic field sensor capable of sensing directional magnetic field components, wherein the at least one output is based on detection of the magnetic field and wherein the at least one magnetic field sensor is positioned in a second well.

Abstract: A method of drilling a well is disclosed. A first estimate is obtained of a location of the well with respect to a reference well at a selected depth. A magnetic measurement is obtained at the selected depth using a sensor. The obtained magnetic measurement is related to a residual magnetic charge distribution in the reference well. An expected value of the magnetic measurement at the selected depth is determined from the residual magnetic charge distribution. A second estimate is obtained of the location of the well using the first estimate of the location, the obtained magnetic measurement and the expected value of the magnetic measurement. A drilling parameter of the well is altered using the second estimate of the location.