Abstract: Systems and methods include a system for deploying and using a customized logging-while-drilling (LWD) tool. A command is provided by a tool control system to a mechanical drive of a LWD tool to cause pads and caliper fingers of the LWD tool to extend radially, lock in place using a locking mechanism, and begin to capture downhole measurements while the LWD tool is deployed in a borehole of a well. Pressure pulse cycles produced by a series of distinct high and low flow rates by the tool control system are provided to create pulses to be detected downhole by pressure transducers. A measurement sequence for caliper and resistivity images is triggered by the tool control system. The measurement sequence is terminated by the tool control system to conserve energy.

Abstract: A system and method for acoustically profiling a wellbore while drilling, and which identifies depths in the wellbore where the wellbore diameter is enlarged or has highly fractured sidewalls. These depths are identified based on monitoring either travel time or signal strength of acoustic signals that propagate axially in the wellbore. Correlating wellbore depth to travel time of a signal traveling downhole inside of a drill string and uphole outside of the drill string yields an average signal velocity in the wellbore. Depths having a lower average signal velocity indicate where the wellbore diameter is enlarged or has highly fractured sidewalls. These depths are also identified by generating separate acoustic signals inside and outside of the drill string, comparing signal strengths of signals reflected from the wellbore bottom, and identifying the depths based on where there is an offset in the strengths of the reflected signals.

Abstract: Acoustic imaging tools and methods use refracted wave amplitudes to generate borehole images, thereby providing a method and tool that is highly sensitive to borehole discontinuities.

Abstract: Apparatus and methods for measurement of pore pressure in rock formations through an open, or cemented and/or cased, borehole are described. Such measurements are achieved using the Dynamic Acoustic Elasticity (DAE) method for characterizing nonlinear parameters by perturbing a selected rock formation volume with a High Amplitude, Low Frequency (HALF) acoustic strain wave, and probing this volume using a Low Amplitude, High Frequency (LAHF) acoustic wave. Time reversal techniques may be employed for focusing acoustic energy Into the formation in the vicinity of the pipe or open hole.

Abstract: Methods and systems are provided that identify relatively large anisotropic horizontal stresses in a formation based on (i) azimuthal variations in the compressional and shear slownesses or velocities of the formation measured from ultrasonic data acquired by at least one acoustic logging tool as well as (ii) cross-dipole dispersions of the formation measured from sonic data acquired by the at least one acoustic logging tool. In addition, the azimuthal variations in the compressional and shear slownesses or velocities of the formation and dipole flexural dispersions of the formation can be jointly inverted to obtain the elastic properties of the rock of the formation in terms of linear and nonlinear constants and the magnitude of maximum horizontal stress of the formation. A workflow for estimating the magnitude of the maximum horizontal stress can employ estimates of certain formation properties, such as overburden stress, magnitude of minimum horizontal stress, and pore pressure.

Abstract: A borehole mapping tool may include a probe casing having first and second ends that is sized to receive at least one location probe. An outer casing sized to be closely received by a borehole surrounds the probe casing so that an interior space is defined therebetween. A first end cap is mounted to a first end of the outer casing so that the first end of the probe casing extends beyond the first end cap. A second end cap is mounted to a second end of the outer casing so that the second end of the probe casing extends beyond the second end cap.

Abstract: A method, including: determining, with a computer, a reflectivity spectrum; generating, with a computer, a target spectrum that is a convolution of a roll-off function and the reflectivity spectrum; and filtering, with a computer, seismic data to cause the seismic data to have the target spectrum.

Abstract: Methods utilizing ultrasonic acoustic logging tools are provided for detecting thin formation layers that present markedly higher compliance than that of the surrounding rock in, for example, a laminated tight hydrocarbon-bearing formation. These layers may be interpreted as presenting potential interfacial and planes of weakness that may have bearing on the extent of a hydraulic fracture propagating across them.

Abstract: Methods are provided for making, processing, and analyzing in situ measurements to indicate presence of thin bedding planes of weakness in a formation. Bedding planes as small as a few inches and smaller are identified using an ultrasonic borehole tool. In one embodiment, detected pseudo-Rayleigh waveforms are processed to determine whether multiple events are detected. If so, lamination and a likely bedding plane of weakness are identified. In another embodiment, a sonic borehole tool is run in conjunction with the ultrasonic borehole tool. Indications of shear and pseudo-shear wave speeds are compared, and where different, a bedding plane of weakness is identified. In another embodiment, a microresistivity imager is run with the ultrasonic borehole tool, and at locations where multiple events are not detected, the image obtained by the imager is inspected to find locations of sharp contrast with adjacent locations to thereby identify bedding planes of weakness.

Abstract: The present invention relates to a system for quickly detecting tunnel deformation, comprising a rail walking mechanism (1) disposed on a subway rail, and an acquisition system (2) disposed on the rail walking mechanism (1); wherein the rail walking mechanism (1) is a T-shaped walking platform, comprising a cross shaft (11), a longitudinal shaft (12) and a stand column (13); the cross shaft (11) and the longitudinal shaft (12) are connected to form the T-shaped platform; tread wheels (16) are disposed at the bottom of the T-shaped platform; one end of the stand column (13) is vertically connected with the cross shaft (11), and the other end of the stand column is used for configuring an operating platform (14) of the acquisition system (2); the acquisition system (2) comprises a fractional laser structured light source (21), industrial focus-fixed cameras (22) and a computer; and the computer is connected with the industrial focus-fixed cameras (22).

Abstract: An inspection system to measure the condition of at least a wall of a ground opening, the inspection system having a head unit for lowering into a borehole during a data collection phase wherein at least one set of test data is collected concerning one or more physical characteristics of the borehole during the data collection phase, the head unit having an internal measurement system and a sensor arrangement with a plurality of sensors facing radially outwardly of a head axis that is generally parallel to at least a portion of a borehole axis, the plurality of sensors allowing the head unit to be moved during the data collection phase without rotation about the head axis, the plurality of sensors at least partially producing the at least one set of test data collected during the data collection phase.

Abstract: A near-bit constant-power wireless short-distance transmission apparatus includes a transmitting portion and a receiving portion. The transmitting portion is connected to a near-bit measurement sub while the receiving portion is connected to a measurement while drilling system. The transmitting portion processes data received by the bit measurement sub and then transmits it to the receiving portion. The receiving portion further processes the information and then transmits it to the measurement while drilling system. An insulating sub is inserted in the transmitting portion and separates the transmitting portion into a transmitting positive pole and a transmitting negative pole, which become electrically isolated from each other. Another insulating sub is inserted in the receiving portion and separates the receiving portion into a receiving positive pole and a receiving negative pole, which become electrically isolated from each other.

Abstract: An example downhole tool incorporating aspects of the present disclosure may include a tool body and a first flexible material coupled to the tool body. A transmitter may be coupled to the first flexible material. A receiver may coupled to the first flexible material, with the receiver having at least two antenna windings positioned in different orientations. A control unit may be communicably coupled to the transmitter and the receiver, the control unit having a processor and a memory device coupled to the processor, the memory device containing a set of instruction that, when executed by the processor, cause the processor to generate an electromagnetic signal in a downhole element using the transmitter, and measure a response of the downhole element to the electromagnetic signal using the at least two antenna windings of the receiver.

Abstract: A data transmission and control device in a multi-node sensor network, comprising a processing control module (110). The processing control module (110) comprises an instruction processing unit, a data processing unit, at least one group of first-type interfaces (J101-J10n), at least one group of second-type interfaces (J201-J20n), one group of fifth-type interfaces (J500) and one group of sixth-type interfaces (J600). The fifth-type interfaces (J500) have communication connections with an external control device (120). The first-type interfaces (J101-J10n) respectively have communication connections with a sensor (140) so as to cooperate with the instruction processing unit to configure and query a parameter of the sensor (140), and to upgrade firmware and report feedback information of the sensor (140) and the processing control module.

Abstract: An example method for removal of stick-slip vibrations may comprise receiving a command directed to a controllable element of a drilling assembly. A smooth trajectory profile may be generated based, at least in part, on the command. A frictional torque value for a drill bit of the drilling assembly may be determined. The example method may further include generating a control signal based, at least in part, on the trajectory profile, the frictional torque value, and a model of the drilling assembly, and transmitting the control signal to the controllable element.

Abstract: A borehole mapping tool may include a probe casing having first and second ends that is sized to receive at least one location probe. An outer casing sized to be closely received by a borehole surrounds the probe casing so that an interior space is defined therebetween. A first end cap is mounted to a first end of the outer casing so that the first end of the probe casing extends beyond the first end cap. A second end cap is mounted to a second end of the outer casing so that the second end of the probe casing extends beyond the second end cap.

Abstract: A photoacoustic imaging apparatus includes a signal processor. The signal processor includes an adding unit configured to add received signals obtained by acoustic wave detecting devices to obtain a summed signal, a normalizing unit configured to normalize the summed signal for each acoustic wave detecting device with reference to an amplitude value in the received signal in the acoustic wave detecting device at the time when a maximum amplitude value in the summed signal is obtained to obtain a normalized signal, a reducing unit configured to subtract the normalized signal from the received signal for each acoustic wave detecting device to obtain a reduced signal in which the amplitude value in the received signal at the time when the maximum amplitude value in the summed signal is obtained is reduced, and an imaging unit configured to generate image data using the reduced signals.

Abstract: A flowmeter for use in a borehole that includes a transmitter and receivers spaced axially away from the transmitter. Energizing the transmitter creates electrical field lines that extend between the transmitter and the receivers, and that pass through fluid flowing past the flowmeter. The magnitude of the electrical field lines at each of the receivers is measured, and varies in response to different types of fluid flowing past the flowmeter, and changes in phase of the fluid. Example transmitters and receivers include coils and electrodes. The transmitters and receivers can define elongate arrays, where the arrays are arranged parallel to, oblique, or perpendicular to an axis of the borehole. Multiple array orientations provide a radial cross sectional image of the flowing fluid. Thus not only can multi-phase flow be detected, but the type of flow regime can be identified.

Abstract: An acoustic logging tool includes a support structure and a set of acoustic transducers coupled to the support structure. The set of acoustic transducers includes a first acoustic transducer and a second acoustic transducer facing the same direction. Each of the first and second acoustic transducers includes a substrate having a first end, a second end, a first side, and a second side. Each acoustic transduce further includes a first piezoelectric element coupled to the first side of the substrate and a second piezoelectric element coupled to the second side of the substrate. The first and second ends of the substrate extend beyond the first and second piezoelectric elements and are fixed to the support structure.

Abstract: Systems, methods, and devices for evaluating proper cement installation in a well are provided. In one example, a method includes receiving acoustic cement evaluation data having a first parameterization. At least a portion of the entire acoustic cement evaluation data may be corrected to account for errors in the first parameterization, thereby obtaining corrected acoustic cement evaluation data. This corrected acoustic cement evaluation data may be processed with an initial solid-liquid-gas model before performing a posteriori refinement of the initial solid-liquid-gas model, thereby obtaining a refined solid-liquid-gas model. A well log track-indicating whether a material behind the casing is a solid, liquid, or gas—may be generated by processing the corrected acoustic cement evaluation data using the refined solid-liquid-gas model.

Abstract: The present invention is a method and an apparatus that can image objects immersed in optically opaque fluids using ultrasound in a confined space and in a harsh environment. If the fluid is not highly attenuating at frequencies above 1 MHz, where commercial ultrasound scanners are available, such scanners can be adapted for imaging in these fluids. In the case of highly attenuating fluids, such as drilling mud, then a low frequency collimated sound source is used.

Abstract: Systems, methods, and software for determining impedance of a casing-cement bond are described. In some aspects, the bond impedance is determined based on results of comparing a measured waveform and a model waveform. The model waveform corresponds to an estimated impedance of the bond and corresponds to a ray tracing of an acoustic signal that accounts for a radiation pattern of the acoustic transmitter and a curvature of the well casing. The measured waveform and the model waveform are generated based on operating an acoustic transmitter and an acoustic receiver within a wellbore comprising the well casing.

Abstract: An example apparatus for downhole cement inspection may include a tool body and an acoustic transmitter coupled to the tool body. An acoustic receiver may be coupled to the tool body at a first distance from the acoustic transmitter. A first array of acoustic receivers may be coupled to and positioned around a circumference of the tool body at a second distance from the acoustic transmitter. The second distance may be greater than the first distance. The acoustic receiver may be one receiver of a second array of acoustic receivers coupled to and positioned around the circumference of the tool body at the first distance. The first distance may be approximately three feet and the second distance may be approximately five feet.

Abstract: An acoustic ranging system utilizes gradiometric data to determine the distance between a first and second well without any knowledge or involvement of the borehole or formation characteristics. An acoustic signal is generated from a downhole or surface source, propagated along a first well, and then received by receivers positioned along the second well. Processing circuitry coupled to the receivers takes a ratio of the absolute signal to the gradient signal in a certain direction to thereby determine the relative position and distance between the two wells.

Abstract: A method for generating a cement bond log, in some embodiments, comprises transmitting sonic or ultra-sonic waves in multiple directions from a logging tool disposed in a wellbore, receiving reflected waves at the logging tool and recording waveforms based on the received waves, processing the waveforms to determine numerical values that indicate a degree of bonding associated with multiple portions of a cement sheath disposed in the wellbore, aggregating the numerical values, and generating a composite image based on the aggregated numerical values.

Abstract: Apparatus and method for characterizing a barrier installed in a borehole traversing a formation including locating an acoustic tool with a receiver and a transmitter at a location in the borehole, activating the acoustic tool to form acoustic waveforms, wherein the receiver records the acoustic waveforms, and processing the waveforms to identify barrier parameters as a function of azimuth and depth along the borehole, wherein the waveforms comprise at least two of sonic signals, ultrasonic pulse-echo signals, and ultrasonic pitch-catch signals.

Abstract: Techniques involve obtaining acoustic data from an acoustic logging tool, where the acoustic data includes waves reflected from the casing, the annular fill material, the formation, and/or interfaces between any of the casing, the annular fill material, and the formation. A crude casing thickness, tool position (e.g., eccentering), mud sound velocity may be estimated using the acoustic data.

Abstract: A device and method for wellbore inspection comprising a downhole tool. The downhole tool may comprise a wireline, a sensor cartridge, and a plurality of centralizers. The method for detecting defects within a wellbore may comprise inserting a downhole tool into a wellbore, wherein the downhole tool comprises a wireline, a sensor cartridge, and a plurality of centralizers. The method also includes producing an acoustic signal with the plurality of centralizers and recording the acoustic signal with a sensor, wherein the sensor records the acoustic signal within an aperture.

Abstract: Controllable tail buoy. At least some of the illustrative embodiments are methods including: towing a sensor streamer and tail buoy through water, the sensor streamer defining a proximal end and a distal end with the tail buoy coupled to the distal end, and the towing with the sensor streamer and the tail buoy submerged; and during the towing controlling depth of the distal end of the sensor streamer at least in part by the tail buoy; and steering the distal end of the sensor streamer at least in part by the tail buoy.

Abstract: An embodiment of a method of estimating characteristics of an earth formation includes: disposing an acoustic tool in a borehole in an earth formation, the acoustic tool including an acoustic multipole transmitter and at least one multipole acoustic receiver; transmitting acoustic signals into the borehole, the acoustic signals generating at least one acoustic body wave that radiates away from the borehole into a far-field formation region; measuring reflected signals including body waves reflected from reflective boundaries in the far-field formation region; identifying a reflective boundary in the formation and reflection attributes associated with the reflective boundary; and estimating at least one of a thickness, distance and a lateral extent of a hydrocarbon formation feature based on the reflected signals and the reflection attributes.

Abstract: An acoustic measurement tool comprises a transmitter for generating acoustic signals and at least one acoustic receiver spaced from the transmitter and configured to receive an acoustic signal, generated by the transmitter, and which has encountered a medium of interest. Moreover, at least one acoustic reference receiver is located adjacent the transmitter and is configured to receive an acoustic signal, generated by the transmitter, prior to the acoustic signal encountering the medium of interest.

Abstract: An instrument for determining fluid properties is provided. The instrument (300) includes a tube (304) receiving the fluid, a single magnet (302) attached to the tube, and a single coil (306) wound around the single magnet. The single coil is coupled to a pulse current source (312) and receives a pulse current that creates a magnetic field in the single coil, the created magnetic field interacting with the single magnet to drive the tube to vibrate. The instrument further includes a detector (306) coupled to the tube, wherein the detector is coupled to measurement circuitry (310) and detects properties of the tube as it vibrates, and the measurement circuitry determines the fluid properties based on the detected properties. The instrument also includes a housing (314) enclosing the tube, the single magnet, and the single coil wound around the single magnet.

Abstract: Apparatus, systems, and methods may operate to emit acoustic pulses into a drilling fluid in a well bore, using a first acoustic transducer in a downhole tool, and detecting the acoustic pulses after reflection from the wall of the well bore, using a second acoustic transducer in the downhole tool. The faces of the first and second acoustic transducers are non-parallel. Further activities include emitting additional acoustic pulses into the drilling fluid using the second acoustic transducer, and detecting them using the second acoustic transducer. The acoustic velocity of the drilling fluid can be determined based on respective travel times. Additional apparatus, systems, and methods are described.

Abstract: Methods and related systems are described for measuring acoustic signals in a borehole during a fracturing operation. The system includes a downhole toolstring designed and adapted for deployment in a borehole formed within a subterranean rock formation. A downhole rock fracturing tool opens and propagates a fracture in the subterranean rock formation. Dipole and/or quadrupole acoustic sources transmit acoustic energy into the subterranean rock formation. A receiver array measures acoustic energy traveling through the subterranean rock formation before, during and after the fracture induction. Geophones mounted on extendable arms can be used to measure shear wave acoustic energy travelling in the rock formation. The toolstring can be constructed such that the sources and receivers straddle the fracture zone during the fracturing.

Abstract: A technique includes providing a source in a first well and a seismic receiver in a second well to detect a seismic event that is caused by the source. The technique includes referencing clocks in the source and receiver to a common reference time frame and determining a time in the reference time frame at which the seismic source generates the seismic event.

Abstract: Methods and apparatus to identify layer boundaries in subterranean formations are described. An example method of identifying a layer boundary of a subterranean formation includes transmitting an acoustic signal from a transmitter into a borehole of the subterranean formation and receiving the acoustic signal at a receiver coupled to the downhole tool and spaced from the transmitter. Additionally, the example method includes logging an energy value associated with the acoustic signal received by the receiver as the downhole tool is moved in the borehole and identifying a change in the logged energy value associated with an impedance change in the subterranean formation to identify the layer boundary.

Abstract: Seismic wave sources and related methods are provided. A seismic wave source includes a housing, plural pillars and an excitation system. The housing is split in two halves along a plane including a longitudinal axis of the housing. The plural pillars are made of piezoelectric elements and are positioned inside the housing to have one end in contact with a semi-cylindrical middle portion of one half of the housing and another end in contact with a semi-cylindrical middle portion of the other half of the housing. The excitation system connected by wires to the plural pillars and is configured to provide electrical signals to the piezoelectric elements. Upon receiving the electrical signals from the excitation system, the pillars generate forces on the housing thereby generating seismic waves.

Abstract: The subject disclosure relates to sonic logging while drilling. A transmitter and at least one receiver are mounted on a drill collar for performing sonic investigations of the formation traversing a borehole.

Abstract: A downhole tool for subsurface disposal is provided. The tool comprises an elongated tool body, an enclosure attached to an exterior surface of the tool body. The enclosure comprises at least one transducer disposed at an angle with respect to a longitudinal axis of the enclosure, and an electronics board coupled to and disposed adjacent to the at least one transducer. The enclosure also defines an internal cavity, and the internal cavity contains a fluid for insulating the at least one transducer from a downhole environment. The fluid is in direct contact with the at least one transducer and the electronics board.

Abstract: A method for attenuating out of band energy emitted from a seismic source used in a marine seismic survey. The method includes disposing the seismic source in a body of water and releasing a gas into a volume of water surrounding the seismic source. The released gas may be configured such that it displaces the volume of water surrounding the seismic source at a rate less than 2.9×106 cubic-meters per cubic-second.

Abstract: An apparatus and method for providing a downhole acoustic source is disclosed. The acoustic source includes a piston configured to oscillate in an axial direction of the acoustic source and produce an acoustic signal in a medium in contact with an exterior surface of the piston, and an elastomer disposed on an interior side of the piston, an acoustic impedance of the elastomer selected to match an acoustic impedance of the piston. A permanent magnet is configured to provide a permanent magnetic field oriented in the axial direction, and a coil disposed on an interior side of the piston produces an alternating magnetic field in the region of the permanent magnetic field. The elastomer may be, for example, a silicon rubber, a silicone jelly, and a silicone oil. A plurality of acoustic sources may be arranged to produce an acoustic dipole configuration or an acoustic quadrupole configuration.

Abstract: An enclosure for housing a transducer and electronics for disposal on a downhole tool. A transducer is disposed at an angle with respect to a longitudinal axis of the enclosure, wherein the enclosure contains a fluid surrounding the transducer. Enclosures also include transducers linked to motor means for selective rotation of the transducers within the enclosure. Enclosures with transducer arrays for phased or targeted signal transmission/detection.

Abstract: A method for attenuating out of band energy emitted from a seismic source used in a marine seismic survey. The method includes disposing the seismic source in a body of water and releasing a gas into a volume of water surrounding the seismic source. The released gas may be configured such that it displaces the volume of water surrounding the seismic source at a rate less than 2.9×106 cubic-meters per cubic-second.

Abstract: Multipole acoustic logging-while-drilling (LWD) tools and associated methods are disclosed herein. In some embodiments, the disclosed acoustic LWD tool comprises a transmitter array and at least one receiver array. The transmitter array generates acoustic waves with an excitation pattern having a cutoff frequency greater than about 3 kHz. The receiver array is spaced apart from the transmitter array and is configured to detect said acoustic waves. Some of the disclosed method embodiments comprise: generating multipole acoustic waves in a fluid-filled borehole using an excitation pattern with a cutoff frequency greater than about 3 kHz; selectively detecting acoustic waves that propagate with said excitation pattern; and determining an acoustic shear wave slowness for a formation penetrated by the borehole.

Abstract: A compact array of transducers is employed as a downhole instrument for acoustic investigation of the surrounding rock formation. The array is operable to generate simultaneously a first acoustic beam signal at a first frequency and a second acoustic beam signal at a second frequency different than the first frequency. These two signals can be oriented through an azimuthal rotation of the array and an inclination rotation using control of the relative phases of the signals from the transmitter elements or electromechanical linkage. Due to the non-linearity of the formation, the first and the second acoustic beam signal mix into the rock formation where they combine into a collimated third signal that propagates in the formation along the same direction than the first and second signals and has a frequency equal to the difference of the first and the second acoustic signals.

Abstract: A borehole receiver for seismic testing has a support frame and an inflatable membrane configured to form a single, compact unit. The inflatable membrane has at least one sensor, such as an accelerometer affixed to the membrane. The at least one accelerometer may be adhesively affixed to an interior portion of the membrane with a cyanoacrylate adhesive. A pneumatic inflation system is used to inflate the membrane with pressurized air. In use, the membrane is slipped over the support frame and secured with a pair of O-rings. Once the borehole receiver is properly positioned in the borehole, pressurized air from the pneumatic inflation system inflates the membrane such that the at least one accelerometer achieves intimate coupling with a wall of the borehole to accurately measure dynamic seismic waves.

Abstract: A vibration source (10) includes an armature bar (12) having a major length dimension, and a driver (20A) positioned about the armature bar. The driver (20A) is movably coupled to the armature bar (12), and includes an electromagnet (40). During operation the electromagnet (40) is activated such that the driver (20A) moves with respect to the armature bar (12) and a vibratory signal is generated in the armature bar. A described method for generating a vibratory signal in an object includes positioning the vibration source (10) in an opening of the object, coupling the armature bar (12) to a surface of the object within the opening, and activating the electromagnet (40) of the driver (20A) such that the driver moves with respect to the armature bar (12) and a vibratory signal is generated in the armature bar and the object.

Abstract: A measurement package for disposal on an apparatus such as a downhole tool or a tool like device. The measurement package including an enclosure, a first acoustic transducer housed within the enclosure, a second acoustic transducer housed within the enclosure and electronics housed within the enclosure that is in communication with the first and second transducers. Further, an acoustic transmitter and receivers can be disposed at an angle with respect to a longitudinal axis of the enclosure. The enclosure can contain attenuative material surrounding the transmitter and receivers, and electronics for controlling the transmitter and receivers and communicating with the downhole tool.

Abstract: In some aspects of the invention, a device, positioned within a well bore, configured to generate and direct an acoustic beam into a rock formation around a borehole is disclosed. The device comprises a source configured to generate a first signal at a first frequency and a second signal at a second frequency; a transducer configured to receive the generated first and the second signals and produce acoustic waves at the first frequency and the second frequency; and a non-linear material, coupled to the transducer, configured to generate a collimated beam with a frequency equal to the difference between the first frequency and the second frequency by a non-linear mixing process, wherein the non-linear material includes one or more of a mixture of liquids, a solid, a granular material, embedded microspheres, or an emulsion.

Abstract: An acoustic borehole logging system for generation and detection of multipole modes used to determine elastic properties of earth formations characterized as inhomogeneous anisotropic solids. The system concurrently generates and senses monopole, dipole, quadrupole and any higher order pole in the borehole/formation system in order to characterize the elastic properties and stress state of material penetrated by the borehole. Multipole modes of all orders are induced simultaneously without the need for separate transmitter and receiver systems. Performance of the logging system is not compromised due to eccentering of the axis of the tool in the borehole, tool tilt with respect to the axis of the borehole, or mismatch of response sensitivity of multiple receivers within the tool.