Abstract: According to embodiments of the disclosure, a downhole tool for taking acoustic measurements in a wellbore is provided. The tool may have an acoustic dipole transmitter with a piston made from a soft magnetic material, mounted on a centering spring between the first coil and the second coil, which moves the piston bi-directionally along a longitudinal axis when energized. The tool may also have a feedback winding on at least one of the first or second coils. The tool may also have a circuit for energizing the first and second coils which includes an input for receiving a signal responsive to the position of the piston relative to the coils and a processor for determining an output waveform used to generate an acoustic signal.

Abstract: An acoustic tool for evaluating a geologic formation includes a housing member disposed between transmitter and receiver sections of the acoustic tool. The housing member defines a change in direction in an acoustic path extending therethrough such that acoustic signals traveling through the housing member are delayed and disrupted. The delay and disruption may isolate the acoustic signals traveling through the housing member from acoustic signals traveling through the geologic formation. Thus, the acoustic tool may facilitate identification and evaluation of acoustic signals traveling through the geologic formation.

Abstract: A disclosed high-purity dipole transmitter has a longitudinal axis, an oscillation axis, and a side axis, each of the axes being mutually orthogonal. The transmitter includes an outer shell having external surfaces for displacing fluid along the oscillation axis. The transmitter also includes a reaction mass positioned inside the outer shell. The transmitter also includes an electromagnetic actuator that drives the outer shell relative to the reaction mass. The transmitter also includes a pair of matching springs separated along the longitudinal axis, where each spring is coupled between the outer shell and the reaction mass to enable compliant dipole motion of the outer shell along the oscillation axis while suppressing motion along other axes. Each spring includes a beam arrangement with each beam extending lengthwise in a direction parallel to the side axis and being thinnest in a direction parallel to the oscillation axis.

Abstract: The disclosure addresses multiple embodiments of an acoustic isolator, and an acoustic logging tool which incorporates the acoustic isolator. The acoustic isolator is configured to minimize acoustic transmissions which could otherwise adversely affect acoustical measurements being made by an acoustic receiver. The described acoustic isolators include a plurality of longitudinally arranged mass members coupled to a central supporting structure, in a configuration to reduce acoustic transmissions in at least selected frequency ranges.

Abstract: A method and system of performing quality control for a downhole tool. An acoustic source is employed to generate a Stoneley wave, and acoustic receivers generate signals indicative of the Stoneley wave. A reference value is calculated from the signals to assess the quality of the receivers. The reference value may be for a selected receiver or a selected receiver ring. The reference value is compared to a threshold deviation to determine if the reference value is outside the threshold deviation. If the reference value is outside of the threshold deviation, the deviation for one of the selected receiver or the selected receiver ring is corrected.

Abstract: A disclosed high-purity dipole transmitter has a longitudinal axis, an oscillation axis, and a side axis, each of the axes being mutually orthogonal. The transmitter includes an outer shell having external surfaces for displacing fluid along the oscillation axis. The transmitter also includes a reaction mass positioned inside the outer shell. The transmitter also includes an electromagnetic actuator that drives the outer shell relative to the reaction mass. The transmitter also includes a pair of matching springs separated along the longitudinal axis, where each spring is coupled between the outer shell and the reaction mass to enable compliant dipole motion of the outer shell along the oscillation axis while suppressing motion along other axes. Each spring includes a beam arrangement with each beam extending lengthwise in a direction parallel to the side axis and being thinnest in a direction parallel to the oscillation axis.

Abstract: Various systems and methods for implementing and using a variable stiffness downhole tool housing include cylindrical segments positioned along a common axis, with a pair of segments each coupled to a bulkhead and positioned at either axial end of the tool housing. The housing also includes a flexible cylindrical sleeve, positioned along the common axis between two of the plurality of cylindrical segments, that includes a first and second region with an outer diameter no larger than a common segment inner diameter and a third region located between the first and second regions and with an outer diameter no larger than a common segment outer diameter (the first and second regions each at least partially inserted into an end of one segment). A stiffness controller controls the stiffness of the tool housing by controlling at least part of an axial force exerted between the two segments.

Abstract: According to embodiments of the disclosure, a downhole tool for taking acoustic measurements in a wellbore is provided. The tool may have an acoustic dipole transmitter with a piston made from a soft magnetic material, mounted on a centering spring between the first coil and the second coil, which moves the piston bi-directionally along a longitudinal axis when energized. The tool may also have a feedback winding on at least one of the first or second coils. The tool may also have a circuit for energizing the first and second coils which includes an input for receiving a signal responsive to the position of the piston relative to the coils and a processor for determining an output waveform used to generate an acoustic signal.

Abstract: An acoustic tool for evaluating a geologic formation includes a housing member disposed between transmitter and receiver sections of the acoustic tool. The housing member defines a change in direction in an acoustic path extending therethrough such that acoustic signals traveling through the housing member are delayed and disrupted. The delay and disruption may isolate the acoustic signals traveling through the housing member from acoustic signals traveling through the geologic formation. Thus, the acoustic tool may facilitate identification and evaluation of acoustic signals traveling through the geologic formation.

Abstract: A method and system for calculating formation porosity is presented. The method includes calculating formation porosity of a borehole by obtaining complex dielectric constant measurements with a high frequency dielectric tool. Next, a dielectric constant of formation water is derived from the complex dielectric constant measurements. Finally, a formation porosity is determined based at least in part on the measured complex dielectric constant and the derived dielectric constant formation water.

Abstract: The disclosure addresses acoustic receivers including an acoustic isolator structure, and an acoustic logging tool which incorporates the acoustic receiver. The acoustic receiver isolation structure is configured to minimize acoustic transmissions which could otherwise adversely affect acoustical measurements being made by an acoustic receiver. The described acoustic receiver includes a plurality of longitudinally arranged mass members coupled to a central supporting structure, in a configuration to reduce acoustic transmissions in at least selected frequency ranges.

Abstract: The disclosure addresses multiple embodiments of an acoustic isolator, and an acoustic logging tool which incorporates the acoustic isolator. The acoustic isolator is configured to minimize acoustic transmissions which could otherwise adversely affect acoustical measurements being made by an acoustic receiver. The described acoustic isolators include a plurality of longitudinally arranged mass members coupled to a central supporting structure, in a configuration to reduce acoustic transmissions in at least selected frequency ranges.

Abstract: In some embodiments, an apparatus and a system, as well as a method and an article, may operate to rotate a rotatable driving member having at least one driving lobe, and to periodically contact at least one cam on a unitary driven member with the at least one driving lobe during rotation of the rotatable driving member, to set the driven member in motion. This motion can be used to launch an acoustic wave along an axis substantially orthogonal to the axis of rotation of the driving member, where the driving member disposed completely within the driven member. The signature of the acoustic wave can be at least partially determined by the profile of the cam and the rotation rate of the driving member. Additional apparatus, systems, and methods are disclosed.

Abstract: The disclosure addresses acoustic receivers including an acoustic isolator structure, and an acoustic logging tool which incorporates the acoustic receiver. The acoustic receiver isolation structure is configured to minimize acoustic transmissions which could otherwise adversely affect acoustical measurements being made by an acoustic receiver. The described acoustic receiver includes a plurality of longitudinally arranged mass members coupled to a central supporting structure, in a configuration to reduce acoustic transmissions in at least selected frequency ranges.

Abstract: Various systems and methods for implementing and using a variable stiffness downhole tool housing include cylindrical segments positioned along a common axis, with a pair of segments each coupled to a bulkhead and positioned at either axial end of the tool housing. The housing also includes a flexible cylindrical sleeve, positioned along the common axis between two of the plurality of cylindrical segments, that includes a first and second region with an outer diameter no larger than a common segment inner diameter and a third region located between the first and second regions and with an outer diameter no larger than a common segment outer diameter (the first and second regions each at least partially inserted into an end of one segment). A stiffness controller controls the stiffness of the tool housing by controlling at least part of an axial force exerted between the two segments.

Abstract: In some embodiments, an apparatus and a system, as well as a method and an article, may operate to rotate a rotatable driving member having at least one driving lobe, and to periodically contact at least one cam on a unitary driven member with the at least one driving lobe during rotation of the rotatable driving member, to set the driven member in motion. This motion can be used to launch an acoustic wave along an axis substantially orthogonal to the axis of rotation of the driving member, where the driving member disposed completely within the driven member. The signature of the acoustic wave can be at least partially determined by the profile of the cam and the rotation rate of the driving member. Additional apparatus, systems, and methods are disclosed.

Abstract: A method for analyzing a subterranean formation porosity is disclosed. The apparent dielectric constant of the subterranean formation and an apparent resistivity of the subterranean formation are measured. The measured values are used to determine a measured formation loss tangent. The formation water loss tangent can be expressed by the water dielectric constant and the water resistivity. The measured formation loss tangent and the formation water loss tangent are then used to determine at least one of an actual dielectric constant of the subterranean formation water and an actual resistivity of the subterranean formation water. The actual formation porosity may be obtained using the estimated water resistivity and water dielectric constant.

Abstract: A method for analyzing a subterranean formation porosity is disclosed. The apparent dielectric constant of the subterranean formation and an apparent resistivity of the subterranean formation are measured. The measured values are used to determine a measured formation loss tangent. The formation water loss tangent can be expressed by the water dielectric constant and the water resistivity. The measured formation loss tangent and the formation water loss tangent are then used to determine at least one of an actual dielectric constant of the subterranean formation water and an actual resistivity of the subterranean formation water. The actual formation porosity may be obtained using the estimated water resistivity and water dielectric constant.

Abstract: A method and system for calculating formation porosity is presented. The method includes calculating formation porosity of a borehole by obtaining complex dielectric constant measurements with a high frequency dielectric tool. Next, a dielectric constant of formation water is derived from the complex dielectric constant measurements. Finally, a formation porosity is determined based at least in part on the measured complex dielectric constant and the derived dielectric constant formation water.

Abstract: A method for analyzing a subterranean formation porosity is disclosed. The apparent dielectric constant of the subterranean formation and an apparent resistivity of the subterranean formation are measured. The measured values are used to determine a measured formation loss tangent. The formation water loss tangent can be expressed by the water dielectric constant and the water resistivity. The measured formation loss tangent and the formation water loss tangent are then used to determine at least one of an actual dielectric constant of the subterranean formation water and an actual resistivity of the subterranean formation water. The actual formation porosity may be obtained using the estimated water resistivity and water dielectric constant.