Abstract: A method of determining anisotropy in a borehole is disclosed. An array of measurements along the borehole is obtained and a first depth in the borehole is selected. An arbitrary plane oriented with respect to the borehole at the first depth is designated and an anisotropy for the first depth with respect to the arbitrary plane is determined. The arbitrary plane is repositioned at the first depth and an anisotropy for different positions of the arbitrary plane at the first depth is determined. A minimum anisotropy coefficient with respect to the arbitrary plane at the first depth is identified based on anisotropy for different positions of the arbitrary plane. An anisotropy tensor for the first depth is then identified.

Abstract: An apparatus for making directional resistivity measurements of a subterranean formation includes a resistivity tool with a longitudinal axis and an outer surface, a first antenna deployed below the outer surface and having an axial mode coil for processing an axial electromagnetic wave and a transverse mode coil for processing a transverse electromagnetic wave to form a joint-coil structure, a second antenna deployed below the outer surface and spaced at an axial distance from the first antenna, at least two sets of slots with different orientations formed on the outer surface. A corresponding method for making directional resistivity measurements includes rotating a resistivity tool in a borehole, utilizing a transmitter-receiver antenna group formed in the resistivity tool to process a superimposition of the axial and transverse electromagnetic waves, and computing a resistivity-related measurement from the superimposition of the axial and transverse electromagnetic waves received on the receiver antenna.

Abstract: Systems and methods are disclosed for reducing boundary-related artifacts in logs taken from resistivity logging tools. Such tools often exhibit “horns” at boundaries between formation beds having different resistivities. A boundary indicator signal serves to identify the location of these boundaries. When derived from an azimuthally-sensitive resistivity tool, the bed boundary indicator may have a magnitude and shape that serves to nearly eliminate the horns even in high-dip angle environments. Logs that are processed to eliminate these artifacts are expected to be more accurate and thus easier to interpret.

Abstract: A method of processing data from an electromagnetic resistivity logging tool which includes a transmitter coil and a receiver coil is disclosed. The electromagnetic resistivity logging tool is placed at a desired location. The transmitter coil and the receiver coil are positioned at a first azimuthal angle. A signal is transmitted from the receiver coil. The receiver coil then receives a signal. The signal at the receiver coil, a tilt angle of the transmitter coil, a tilt angle of the receiver coil and the first azimuthal angle are then used to calculate a first complex voltage representing at least one component of the received signal.

Abstract: The present disclosure relates to a method to determine the vertical resistivity of a subsurface formation. A downhole logging tool having a plurality of spaced antennas, at least one of which is a transverse antenna, at least two of which are tilted antennas, and at least two of which are axial antennas is provided. Measurements involving the transverse and/or the tilted antennas of the downhole logging tool are obtained. Voltage ratios are formed using the measurements, and conditioning factors are formed by raising the determined voltage ratios not involving the transverse antenna to some arbitrary power. The sum of the exponents of the conditioning factors preferably equals one. A voltage ratio involving the transverse antenna is multiplied by the conditioning factors, and the vertical resistivity of the subsurface formation is determined using the resulting ratio.

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: A microresistivity logging tool includes a transmitter coil and at least one receiver coil deployed on a tool body. The transmitter coil and receiver coil define axes that are preferably substantially perpendicular to the tool axis.

Abstract: A method comprising: estimating a change in a characteristic of a subterranean formation into which a fluid has been injected via a well extending into the subterranean formation; building a multi-dimensional model balancing mass of the injected fluid, wherein the model is based on the estimated characteristic change; utilizing the model to determine the sensitivity of a borehole gravity tool in the well; measuring gravity with the borehole gravity tool at a plurality of stations along the well; and utilizing the model and the gravity measurements to locate the injected fluid in the subterranean formation.

Abstract: An apparatus and method for estimating a parameter of interest in a borehole penetrating an earth formation using a receiver and a transmitter, both disposed on a carrier, with aligned magnetic moments to correct for bending of carrier during borehole investigations. The apparatus may include a transmitter with at least two substantially perpendicular coils and a receiver with at least one coil oriented with at least one or the transmitter coils. The method may include aligning the magnetic moment of the transmitter and the magnetic moment of the receiver prior to estimating the parameter of interest. The method may include supplying a constant electric current to one of the transmitter coils while supplying a varying electric current to another of the transmitter coils. The method may include estimating a direction of bending or angle of bending of the carrier.

Abstract: A logging while drilling tool includes a directional resistivity antenna and an antenna shield having. The shield has at least one slot having at least one electrically open end formed therein. The antenna shield may include a base portion and a plurality of spaced apart fingers extending away from the base portion such that the finger ends are electrically isolated from the tool body and from one another. The antenna shield may alternatively include a plurality of spaced apart plates that are electrically isolated from the tool body and from one another. These antenna shields have been found to provide suitable physical protection for sensitive antenna components while at the same time being substantially transparent to both z-mode and x-mode electromagnetic waves.

Abstract: An apparatus configured to evaluate an earth formation that includes a tuned transmitter antenna and an untuned broadband receiver antenna. The transmitter antenna being configured to generate electromagnetic energy and the untuned broadband antenna configured to produce an output responsive to the generated electromagnetic energy. The untuned, broadband receiver antenna is configured reduce to reduce tool complexity, antenna coupling, and cross-talk between conductors to the antenna assemblies. The method includes using the apparatus in earth formation evaluation.

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: A directional resistivity tool includes a pair of transmitters deployed between at least one pair of receivers. Each of the transmitters and receivers preferably includes collocated z-mode and x-mode antennae. Exemplary embodiments may further include additional receivers, for example, additional pairs of receivers deployed axially about the transmitters or one or more deep reading receivers deployed on one axial end of the transmitters. Tools in accordance with the invention enable directional resistivity measurements to be acquired at multiple depths of investigation using fewer transmitter firings than conventional tools.

Abstract: A system and method to determine earth formation properties by positioning a logging tool within a wellbore in the earth formation, the logging tool having a tool rotation axis and a first, a second, and a third tilted transmitter coil, and a tilted receiver coil; rotating the logging tool about the tool rotation axis; energizing each transmitter coil; measuring a coupling signal between each transmitter coil and the receiver coil for a plurality of angles of rotation; determining a coupling tensor; and determining the earth formation properties using the coupling tensor.

Abstract: Methods and related systems are described for making an electromagnetic induction survey of a formation surrounding a cased section of a borehole. An electromagnetic transmitter and/or receiver is deployed into the cased section of the borehole. Electromagnetic survey measurements and impedance measurements relating to impedance of the transmitter and/or receiver are made while deployed in the section of the borehole. Compensation is made for the attenuation amplitude and/or phase in the electromagnetic survey measurements due to the conductive casing. The compensation is based on the impedance measurements and equivalent circuit parameters. The impedance measurements are correlated with numerical modeling results of a purely inductive electromagnetic transducer, and calculated equivalent circuit parameters are combined with the numerical modeling results.

Abstract: This disclosure relates to a downhole logging tool for acquiring data in an earth formation. In one embodiment, the downhole logging tool has a tool body with a longitudinal axis, a set of antennas located on the tool body and including coil windings forming a closed-loop pattern, and a shield disposed over the antennas and having an arrangement of slots with each slot being substantially perpendicular to a proximate portion of at least one of the underlying coil windings, wherein the path length around each slot is more than twice the length of the distance between the slot and a directly adjacent slot along an arc of the coil windings. The downhole logging tool may be a wireline or while-drilling tool, and it may be an induction or propagation tool.

Abstract: Methods and related systems are described for making electromagnetic measurements of a subterranean rock formation through a conductive casing of a borehole. A number of transmitters/receivers are deployed into single well having a conductive casing. A magnetic field is induced through the conductive casing and into a surrounding subterranean rock formation, and the magnetic field is detected by the receivers. The receivers have main windings, feedback winding and bucking windings. One of the receiver coils in the tool string is excited at a time, and induced voltages at all of the other receiver coils, either in straight mode, or in feedback mode, are measured.

Abstract: A method for drilling a wellbore proximate a salt structure includes measuring formation resistivity azimuthally. A map of spatial distribution of resistivity is determined from the azimuthal resistivity measurements. A distance from the wellbore to an edge of the salt structure is determined from the three dimensional volume map.

Abstract: A method for determining orientation of an electrically conductive formation proximate an electrically substantially non-conductive formation includes measuring multiaxial electromagnetic induction response within the substantially non-conductive formation using an instrument disposed in a wellbore drilled through the formations. A difference from zero conductivity is determined for each component measurement of the multiaxial electromagnetic induction response. The differences are used to correct the measured response of each component measurement in the electrically conductive response. The corrected component measurements are used to determine the orientation of the conductive formation.

Abstract: A downhole induction resistivity assembly comprises a mandrel. Disposed around the mandrel are coils of wire disposed circumferentially around magnetic field concentrators. The coils of wire and the magnetic field concentrators are disposed on an outer diameter of the mandrel. A magnetic field deflector, of magnetic permeability greater than the mandrel, is disposed intermediate the coils and the mandrel.

Abstract: A transmitter antenna assembly for transient electromagnetic well logging instrument comprises an antenna coil coupled with a current source and a magnetic core having residual magnetization. Switching current in the antenna coil results in magnetization reversal in the magnetic core and change in magnetic dipole moment of the antenna. After the magnetization reversal is complete the current is removed and the new vector of magnetic dipole of the antenna maintains constant (steady-state phase of the antenna dipole) due to magnetic hysteresis of magnetic material employed for the magnetic core. No power expenditure during the steady-state phase of the magnetic dipole facilitates highly effective generation and fast switching of a large magnetic dipole. The magnetic core also serves as a shield between the antenna coil and any conductive part of the antenna assembly.

Abstract: A method is provided for determining formation resistivity, anisotropy and dip from wellbore measurements includes moving a well logging instrument through subsurface formations. The instrument includes longitudinal magnetic dipoles and at least one of tilted and transverse magnetic dipoles. Formation layer boundaries and horizontal resistivities of the formation layers are determined from longitudinal magnetic dipole measurements. Vertical resistivities of the formation layers are determined by inversion of anisotropy sensitive measurements. Improved vertical resistivities of the formation layers and dips are determined by inverting symmetrized and anti-symmetrized measurements. Improved vertical resistivities, improved boundaries and improved dips are determined by inversion of the all dipole measurements. Improved horizontal resistivities, further improved layer boundaries and further improved dips are determined by inversion of all dipole measurements.

Abstract: Methods and related systems are described for determining the casing attenuation factor for various frequencies from measurements of the impedance of the transmitting or receiving coil of wire of. The compensation is based on two relationships. The first relationship is between one or more measured impedance parameters and the product of casing conductivity, casing thickness and electromagnetic frequency. The second relationship is between the casing correction factor and the product of casing conductivity, casing thickness and electromagnetic frequency.

Abstract: A combined resistivity tool incorporating both induction/propagation antennas and lateral resistivity antennas disposed in recesses of downhole tubulars, in which a lateral resistivity antenna includes an insulating base layer disposed in the recess; a toroidal antenna disposed over the insulating base layer; and a shield disposed over the recess.

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. A first transmitter electrode and a second transmitter electrode are disposed at the carrier and configured to inject an electrical current into the earth formation. A first measurement electrode and a second measurement electrode are disposed at the carrier and configured to measure the electrical current to estimate the property of the earth formation. A first bucker amplifier is coupled to the first measurement electrode and a second bucker amplifier is coupled to the second measurement electrode, wherein the first and second bucker amplifiers are configured to equalize electrical potentials of areas in front of the first and second measurement electrodes.

Abstract: A method for determining a formation type within a wellbore includes forming the wellbore such that the wellbore intersects fractures within a formation. Hydrocarbons are produced from the formation. An induction tool is disposed into the wellbore after producing the hydrocarbons. A resistivity of a portion of the formation is measured with the induction tool. The resistivity of the portion of the formation is compared with a known formation type. The formation type of the portion of the formation is determined based on the resistivity. A characteristic of the formation type is output.

Abstract: The invention is a method for inverting reservoir bi-axial anisotropy and identifying complicated fracture/cross-bedding system (104) by using tri-axial induction logs and wellbore survey/image log data. An inversion method is disclosed that uses all nine components that can be measured by tri-axial induction tools (101), plus borehole azimuth and deviation data, to solve for the tri-axial induction response in an arbitrary anisotropic formation due to the non-orthogonal bedding plane and fracture plane (or cross bedding plane). A mathematical formula is provided relating the conductivity tensor in the tool's reference frame to the conductivity tensor in a reference plane associated with the fracture/cross bedding planes (102). This equation is inverted (103) to yield the conductivity tensor components in the fracture/cross bedding coordinate system, along with dip and azimuth angles for both the fracture/cross bedding planes and the tool.

Abstract: Methods and related systems are described for making an electromagnetic induction survey of a formation surrounding a cased section of a borehole. An electromagnetic transmitter and/or receiver is deployed into the cased section of the borehole. Electromagnetic survey measurements and impedance measurements relating to impedance of the transmitter and/or receiver are made while deployed in the section of the borehole. Compensation is made for the attenuation amplitude and/or phase in the electromagnetic survey measurements due to the conductive casing. The compensation is based on the impedance measurements and equivalent circuit parameters. The impedance measurements are correlated with numerical modeling results of a purely inductive electromagnetic transducer, and calculated equivalent circuit parameters are combined with the numerical modeling results.

Abstract: A down-hole tool provided with a transmitter system for inducing a transient electromagnetic field in an earth formation has an induction coil with a number of windings to generate essentially a magnetic dipole field. The number of windings is divided into two or more groups of windings arranged to cooperatively generate the essentially magnetic dipole field when energized. Switching means are arranged to essentially simultaneously terminate the energizing of the groups of windings. The groups of windings are electrically isolated from each other or connected in parallel to each other, at least when the energizing is terminated. A transient electromagnetic field may thus be induced in an earth formation by essentially simultaneously terminating energizing each group of windings by operating the switching means. A transient electromagnetic response signal may be recorded, and used in a method of producing a mineral hydrocarbon fluid.

Abstract: An apparatus, method and computer-readable medium are provided for estimating a resistivity property of an earth formation. A logging tool includes a first antenna arrangement and a second antenna arrangement of the logging tool; and at least one device for maintaining the first antenna arrangement and the second antenna arrangement in proximity to a wall of the borehole. The first antenna arrangement and the second antenna arrangement may be at substantially the same axial location on the logging tool. Alternately, the first antenna arrangement and the second antenna arrangement may be at different axial positions on the logging tool. Extendible arms of the logging tool are configured to extend one or more of the first antenna arrangement and the second antenna arrangement against a face of the borehole.

Abstract: The disclosure provides an apparatus and method for estimating one or more formation properties downhole. The apparatus includes a tool body that has a longitudinal axis. The tool body has a number of metallic pillars that are attached to or are an integral part of the tool body. Antenna wires may be positioned on the tool body between the pillars in a plurality of orientations to provide a multidirectional antenna. An insulating material is used to cover the antenna wires. A high magnetic permeability material is placed between the antenna wires and the tool body. The antenna may be configured to operate as a transmitter or as a receiver for a resistivity sensor or an NMR sensor.

Abstract: The present disclosure relates to determining attenuation factors relating to an electromagnetic signal passing through, a conductive material seen by a real sensor. A sensor is provided and disposed proximate to the material. An alternating current is passed through the sensor and the impedance of the sensor is measured. The impedance of an ideal coil is obtained from the measured impedance using electromagnetic modeling combined with a circuit analysis of the coil impedance, and the attenuation factors for the real coil in straight or feedback mode are determined by electromagnetic modeling of casing attenuation factors and impedance of an ideal coil combined with equivalent circuit modeling of the sensor transfer functions. The attenuation factors seen by the real sensor may be determined in real-time or post-survey. The material may be magnetic or non-magnetic.

Abstract: A method and apparatus provide a time-dependent calibration to essentially eliminate pipe effect in pulse-induction logging while drilling. Use of two receivers to provide calibration and measurement information allows determination of formation properties in a downhole environment while eliminating the effect of tool effects.

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 current sensor measures an electrical current flowing in well casing or other magnetic structure. The current sensor can be installed in a tool for performing electromagnetic (EM) induction surveying in a wellbore lined with an electrically conductive casing. The tool includes an EM element to transmit or receive a magnetic field through the casing. The measured current using the current sensor can be used to relate the change of casing effect on the EM element (e.g., an induction receiver) placed inside the well casing for performing the EM induction survey.

Abstract: Methods and systems for characterizing a formation are disclosed. A tool is placed in the formation. The tool comprises a perpendicular antenna set and a parallel antenna set. The perpendicular antenna set comprises at least one transmitter antenna oriented perpendicular to at least one receiver antenna and the parallel antenna set comprises at least one transmitter antenna oriented parallel to at least one receiver antenna. Data is obtained from the tool and used to determine a compensated geosignal for each of the perpendicular antenna set and the parallel antenna set. The determined compensated geosignal is used to characterize the formation.

Abstract: A transient electromagnetic (TEM) signal is recorded in an earth formation during vibration of a logging tool. Concurrently, accelerometer measurements are made. The accelerometer measurements are used to correct the TEM signal for the vibration using the accelerometer measurement and a transfer function relating the TEM signal and the accelerometer. The transfer function may be determined using measurements in a water tank or by using the tail end of the TEM measurements.

Abstract: A downhole induction resistivity assembly that comprises a downhole tool string component. The tool string component comprises an induction transmitter. The transmitter is adapted to induce an induction field in the surrounding formation. A first induction receiver is spaced apart from the transmitter and is adapted to measure the induction field. A magnetic field generating mechanism is disposed adjacent on either or both sides of the transmitter and adapted to guide the transmitter's signal into the formation. A second induction receiver is disposed in close proximity to the magnetic field generating mechanism and is adapted to measure the magnetic field generated by the mechanism.

Abstract: Structure for deep MWD resistivity measurements suitable for both geo-steering and measurements ahead of the drill bit is disclosed. Alternating current is transmitted through a loop and an induction signal is measured by a two-coil bucking receiving system placed at some distance from the transmitter. To further reduce a parasitic effect of the currents in the pipe, a conductive copper shield wrapping around the pipe is used. The length of the shield is about one and one-half to two times longer than the longest transmitter/receiver spacing of the structure. The transmitter/receiver system is located in the center of the described electromagnetic shield.

Abstract: A method for providing an image of a formation surrounding a wellbore, includes: obtaining an apparent conductivity curve from main components of resistivity measurements of the formation; performing fitting for cross-components of the resistivity measurements; calculating scaling factors from the cross-component data; scaling apparent conductivity data by the calculated scaling factors; and plotting the scaled conductivity data to provide the image of the anisotropic formation. A system and a computer program product are disclosed.

Abstract: Methods for imaging geological structures include injecting magnetic materials into the geological structures, placing at least one magnetic probe in a proximity to the geological structures, generating a magnetic field in the geological structures and detecting a magnetic signal. The at least one magnetic probe may be on the surface of the geological structures or reside within the geological structures. The methods also include injecting magnetic materials into the geological structures, placing at least one magnetic detector in the geological structures and measuring a resonant frequency in the at least one magnetic detector. Methods for using magnetic materials in dipole-dipole, dipole-loop and loop-loop transmitter-receiver configurations for geological structure electromagnetic imaging techniques are also disclosed.

Abstract: Logging tools having protected tilted antennas are disclosed, along with construction methods therefor. In one method embodiment, a tilted antenna on a retrievable segment of a downhole tool is constructed by: forming an elliptical recess on the segment; forming an antenna within the elliptical recess; and forming an elliptical pattern of windows over and perpendicular to the axis of the elliptical antenna. Some tool embodiments comprise a retrievable segment of a downhole tool having an elliptical recess; an elliptical antenna disposed within the elliptical recess; and an elliptical pattern of windows formed over and perpendicular to the plane of the elliptical antenna.

Abstract: An apparatus for evaluating an earth formation, the apparatus including: a logging tool configured to be conveyed through a borehole penetrating the earth formation; a coil inductively coupled to the earth formation, the coil being disposed at the logging instrument; and a circuit coupled to the coil wherein the circuit and the coil form an oscillator circuit, the oscillator circuit being configured to oscillate when a circuit parameter of the oscillator circuit satisfies an oscillation criterion, the circuit parameter being related to a property of the earth formation.

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

Abstract: 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: An eddy current probe testing apparatus structured to operate concurrently in a driver pick-up mode and said impedance mode is provided. The eddy current probe has two coils. The eddy current probe testing apparatus also includes a signal producing device, an output device, and a switch assembly. The switch assembly is structured to switch how an input signal from the signal producing device is provided to the two coils.

Abstract: A method for determining electromagnetic induction properties of subsurface rock formations includes determining an eccentering angle of a well logging instrument disposed in a wellbore. The instrument includes at least one triaxial induction transmitter and at least one triaxial induction receiver. The eccentering angle is determined from symmetric cross component measurement differences. The triaxial induction measurements made from the at least one receiver are rotated to an apparent eccentering angle of zero. At least one electromagnetic induction property is determined from the rotated triaxial induction measurements.

Abstract: A downhole drill string component is disclosed comprising a substantially cylindrical cage with a hollow bore. An inner diameter of the cage is slideably connectable to a mandrel. A stab connection originates from one end of the cage and a plurality of downhole drill string instruments is circumferentially disposed around an outer diameter of the cage.

Abstract: Method, devices and systems are provided for measuring deformation in subterranean formations. Such methods include introduction of spaced-apart depth magnetic markers along the longitudinal length of a well bore and measuring the position of each depth marker over time so as to determine deformation of the subterranean formation. In certain embodiments, depth markers comprise rare earth magnets. In further embodiments, orientation of each magnetic bullet is determined over time to determine the change in orientation of each magnetic bullet. Advantages of the methods and devices herein include, but are not limited to, improved accuracy and reliability of deformation measurements and reduced environmental impact due to the avoidance of radioactive markers used by the present invention.

Abstract: A logging tool and method to make subsurface measurements is disclosed, wherein the tool is placed within a borehole penetrating a formation. The tool has a transmitter antenna and a receiver antenna spaced apart along a longitudinal axis of the tool, and at least one of the transmitter or receiver antennas has a dipole moment that is non-coaxial with the longitudinal axis of the tool. The at least one non-coaxial antenna can rotate relative to the other antenna. Energy is transmitted from the transmitter antenna and a signal associated with the transmitted energy is measured at the receiver antenna while the at least one non-coaxial antenna rotates relative to the other antenna.