Abstract: A method to obtain gain-corrected measurements. A measurement tool having one or more arrays is provided, wherein the arrays include two co-located triaxial transmitters and two co-located triaxial receivers. Measurements are obtained using the transmitters and the receivers. Impedance matrices are formed from the obtained measurements and the impedance matrices are combined to provide gain-corrected measurements. The apparatus may alternatively be a while-drilling logging tool having one or more arrays, wherein each array comprises a transmitter, a receiver, and a buck, and wherein the signal received by the receiver is subtracted from the signal received by the buck or vice versa. A slotted shield may be incorporated into either embodiment of the tool. The slots may form one or more island elements. A material is disposed in the slots. The islands and shield body have complementary tapered sides that confine the islands within the shield body.

Abstract: A method for calibrating an electromagnetic core analysis tool is disclosed. The method includes disposing a tilted test loop inside of or outside of a tool having more than one antenna. A uniform test pack, a layered test pack, and an effective media test pack are each disposed in the tool. A signal is induced in a receiver antenna in the tool when a second antenna is energized with a known current of a known frequency. The induced signal is measured and a calibration gain and offset is determined. A corrected signal is produced and compared with the determined signal based on a forward model.

Abstract: An electromagnetic method for obtaining a dip azimuth angle from downhole electromagnetic measurements includes acquiring electromagnetic measurement data in a subterranean borehole from at least one measurement array. The electromagnetic measurement data is processed by a least squares method to obtain the dip azimuth angle. Related systems and apparatuses are also disclosed herein.

Abstract: The apparatus employs the remote field eddy-current (RFEC) inspection technique to electromagnetically measure physical parameters of a metallic pipe. RFEC devices inserted into and displaced along a cylindrical pipes may be used to measure the ratio of pipe thickness to electromagnetic skin-depth and thus allow for the non-invasive detection of flaws or metal loss. Typically these RFEC thickness measurements exhibit a so-called double-indication of flaws, an undesired artifact due to a double-peaked geometrical sensitivity function of the device. The method describes a means by which this double indication artifact may be removed by an appropriate processing of RFEC measurements performed by an apparatus specifically designed for this purpose. The invention is particularly well designed for applications in the oilfield industry.

Abstract: A method for calibrating an electromagnetic core analysis tool is disclosed. The method includes disposing a tilted test loop inside of or outside of a tool having more than one antenna. A uniform test pack, a layered test pack, and an effective media test pack are each disposed in the tool. A signal is induced in a receiver antenna in the tool when a second antenna is energized with a known current of a known frequency. The induced signal is measured and a calibration gain and offset is determined. A corrected signal is produced and compared with the determined signal based on a forward model.

Abstract: A method for correcting formation properties due to effects of a borehole is disclosed. The method includes obtaining voltage measurements using a logging tool disposed in a borehole penetrating a subsurface formation. The method further includes using a processor to: determine a tensor for the formation using the voltage measurement. For a given set of parameters, the processor determines, based upon the voltage measurements, a parameter value for each parameter in a subset of the set of parameters.

Abstract: A logging tool for use in a wellbore is disclosed herein. The logging tool may include a hollow body. Two or more antenna coils may be disposed at least partially within the body and be axially aligned with one another with respect to a longitudinal axis through the body. Each of the two or more antenna coils, in an unrolled view, may have the form of a sinusoidal function that includes a harmonic of order greater than one.

Abstract: A downhole logging tool includes a tool body having a co-located set of antennas located on the tool body and first and second antennas formed from respective first and second pairs of coil windings having a closed-loop pattern. Both the first and second pair of coil windings are arranged on diametrically opposed antenna sections. A cylindrical shield is disposed over the co-located set of antennas and has a first set of vertical slots arranged interposed between each of the underlying antenna sections, a second set of vertical slots arranged over each of the underlying antenna sections, with each of the second set of vertical slots being perpendicular to a portion of the coil winding in the underlying antenna section, and a set of non-vertical slots arranged over each the underlying antenna sections. Each of non-vertical slots is perpendicular to a portion of the coil winding in the underlying antenna section.

Abstract: The apparatus employs the remote field eddy-current (RFEC) inspection technique to electromagnetically measure physical parameters of a metallic pipe. RFEC devices inserted into and displaced along a cylindrical pipes may be used to measure the ratio of pipe thickness to electromagnetic skin-depth and thus allow for the non-invasive detection of flaws or metal loss. Typically these RFEC thickness measurements exhibit a so-called double-indication of flaws, an undesired artifact due to a double-peaked geometrical sensitivity function of the device. The method describes a means by which this double indication artifact may be removed by an appropriate processing of RFEC measurements performed by an apparatus specifically designed for this purpose. The invention is particularly well designed for applications in the oilfield industry.

Abstract: A downhole logging tool includes a tool body having a co-located set of antennas located on the tool body and first and second antennas formed from respective first and second pairs of coil windings having a closed-loop pattern. Both the first and second pair of coil windings are arranged on diametrically opposed antenna sections. A cylindrical shield is disposed over the co-located set of antennas and has a first set of vertical slots arranged interposed between each of the underlying antenna sections, a second set of vertical slots arranged over each of the underlying antenna sections, with each of the second set of vertical slots being perpendicular to a portion of the coil winding in the underlying antenna section, and a set of non-vertical slots arranged over each the underlying antenna sections. Each of non-vertical slots is perpendicular to a portion of the coil winding in the underlying antenna section.

Abstract: The apparatus employs the remote field eddy-current (RFEC) inspection technique to electromagnetically measure physical parameters of a metallic pipe. RFEC devices inserted into and displaced along a cylindrical pipes may be used to measure the ratio of pipe thickness to electromagnetic skin-depth and thus allow for the non-invasive detection of flaws or metal loss. Typically these RFEC thickness measurements exhibit a so-called double-indication of flaws, an undesired artifact due to a double-peaked geometrical sensitivity function of the device. The method describes a means by which this double indication artifact may be removed by an appropriate processing of RFEC measurements performed by an apparatus specifically designed for this purpose. The invention is particularly well designed for applications in the oilfield industry.

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: A method for correcting formation properties due to effects of a borehole is disclosed. The method includes obtaining voltage measurements using a logging tool disposed in a borehole penetrating a subsurface formation. The method further includes using a processor to: determine a tensor for the formation using the voltage measurement. For a given set of parameters, the processor determines, based upon the voltage measurements, a parameter value for each parameter in a subset of the set of parameters.

Abstract: A method to determine one or more borehole corrected formation properties using measurements made using a logging tool disposed in a borehole penetrating an earth formation is disclosed. The measurements are used to determine an apparent conductivity tensor for the formation and, for a set of parameters, a parameter value for each parameter in a subset of the set of parameters. A parameter value for each parameter in the set of parameters not in the subset is provided and a borehole-inclusive modeled conductivity tensor is computed. The apparent conductivity tensor and the borehole-inclusive modeled conductivity tensor are iteratively used to optimize the parameter values, and the optimized parameter values are used to compute an optimized conductivity tensor. A borehole corrected conductivity tensor is computed using the optimized conductivity tensor, and the borehole corrected formation properties are determined using the borehole corrected conductivity tensor and/or the optimized parameter values.

Abstract: A method to obtain gain-corrected measurements. A measurement tool having one or more arrays is provided, wherein the arrays include two co-located triaxial transmitters and two co-located triaxial receivers. Measurements are obtained using the transmitters and the receivers. Impedance matrices are formed from the obtained measurements and the impedance matrices are combined to provide gain-corrected measurements. The apparatus may alternatively be a while-drilling logging tool having one or more arrays, wherein each array comprises a transmitter, a receiver, and a buck, and wherein the signal received by the receiver is subtracted from the signal received by the buck or vice versa. A slotted shield may be incorporated into either embodiment of the tool. The slots may form one or more island elements. A material is disposed in the slots. The islands and shield body have complementary tapered sides that confine the islands within the shield body.

Abstract: The present invention relates to a downhole logging tool having on its tool body a set of co-located antennas, one or more additional antennas spaced longitudinally apart from the set of co-located antennas, an electromagnetically transparent shield circumferentially surrounding the set of co-located antennas, and an electromagnetically transparent shield circumferentially surrounding each of the one or more additional antennas. The downhole logging tool may be a wireline or while-drilling tool, and it may be an induction or propagation tool. The shields may have slots that are locally perpendicular to the windings of underlying coil antennas.

Abstract: A wellbore tool for locating a target wellbore containing a conductive member from a second wellbore and directing the trajectory of the second wellbore relative to the target wellbore includes an electric current driver having an insulated gap; a three-axis magnetometer positioned within a non-magnetic housing that is disposed within a non-magnetic tubular, the three-axis magnetometer positioned below the electric current driver; a drill bit positioned below the three-axis magnetometer; a hollow tubular connected between the electric current driver and the three-axis magnetometer; and a measurement-while-drilling tool. The current driver generates an electric current across the gap to the portion of the tool below the insulated gap. In a method a current is generated across the insulated gap to the portion of the tool below the insulated gap to the conductive material in the target wellbore returning to a portion of the bottom hole assembly above the insulated gap thereby producing a target magnetic field.

Abstract: The apparatus employs the remote field eddy-current (RFEC) inspection technique to electromagnetically measure physical parameters of a metallic pipe. RFEC devices inserted into and displaced along a cylindrical pipes may be used to measure the ratio of pipe thickness to electromagnetic skin-depth and thus allow for the non-invasive detection of flaws or metal loss. Typically these RFEC thickness measurements exhibit a so-called double-indication of flaws, an undesired artifact due to a double-peaked geometrical sensitivity function of the device. The method describes a means by which this double indication artifact may be removed by an appropriate processing of RFEC measurements performed by an apparatus specifically designed for this purpose. The invention is particularly well designed for applications in the oilfield industry.

Abstract: A wellbore tool for locating a target wellbore containing a conductive member from a second wellbore and directing the trajectory of the second wellbore relative to the target wellbore includes an electric current driver having an insulated gap; a three-axis magnetometer positioned within a non-magnetic housing that is disposed within a non-magnetic tubular, the three-axis magnetometer positioned below the electric current driver; a drill bit positioned below the three-axis magnetometer; a hollow tubular connected between the electric current driver and the three-axis magnetometer; and a measurement-while-drilling tool. The current driver generates an electric current across the gap to the portion of the tool below the insulated gap. In a method a current is generated across the insulated gap to the portion of the tool below the insulated gap to the conductive material in the target wellbore returning to a portion of the bottom hole assembly above the insulated gap thereby producing a target magnetic field.

Abstract: The present invention relates to a downhole logging tool having on its tool body a set of co-located antennas, one or more additional antennas spaced longitudinally apart from the set of co-located antennas, an electromagnetically transparent shield circumferentially surrounding the set of co-located antennas, and an electromagnetically transparent shield circumferentially surrounding each of the one or more additional antennas. The downhole logging tool may be a wireline or while-drilling tool, and it may be an induction or propagation tool. The shields may have slots that are locally perpendicular to the windings of underlying coil antennas.