Abstract: A downhole acoustic tool and method of use are provided. The acoustic tool includes an acoustic tool body. In addition, a transmitter section located along the acoustic tool body, including four or more transmitters to be driven so as to excite multi-mode waveforms. The acoustic tool further includes an array receiver section located along the acoustic tool body, containing a receiver sub-section comprising four or more receivers axially aligned with the four or more transmitters and spaced axially apart from the transmitter section. The acoustic tool also includes a processor configured to drive the transmitter section to excite multi-mode waveforms and to extract the multi-mode waveforms detected by the receiver section for interpretation of formation properties. A method for measuring a formation using the described acoustic tool is also provided.

Abstract: A method of model-based acoustic measurements for a wellbore is disclosed. The method comprises creating an interpretation chart of acoustic measurements by a downhole tool in a wellbore using a numerical modeling and performing an evaluation with respect to the wellbore based on the interpretation chart.

Abstract: Methods and systems of measuring acoustic signals via a borehole wall are disclosed. One or more non-contact magneto-dynamic sensors are configured or designed for deployment at at least one depth in a borehole. The magneto-dynamic sensor comprises a coil excited by an electric current and a circuitry for outputting a signal corresponding to a time-varying impedance of the coil. A processor is configured to perform signal processing for deriving at least one of a magnitude or a frequency of vibration of the borehole wall based on the output signal from the circuitry.

Abstract: A technique facilitates monitoring of acoustic signals to measure a velocity vector of a borehole. Acoustic sensors are arranged in a desired acoustic sensor array and positioned along a body of a tool, e.g. a sonic logging tool. The acoustic sensor array is then positioned in fluid along a wall of a borehole formed in a subterranean formation. The acoustic sensors are used to collect acoustic signal data while the acoustic sensors are maintained in a non-contact position with respect to the wall of the borehole. The data may be processed to determine the desired velocity vector.

Abstract: A technique facilitates use of acoustic measurements to enable geo-steering during a well operation. A steerable well string is provided with acoustic systems used to collect data which is then processed to determine geo-steering inputs. In some applications, the well string may comprise a coiled tubing drilling tool. The coiled tubing drilling tool or other well string tool is combined with an azimuthally distributed pitch-catch micro-sonic sensor system and an azimuthally distributed ultrasonic pulse-echo transducer system. Data from these two systems is provided to a processing system which processes the data to determine, for example, real-time, geo-steering inputs. These inputs may then be used to more effectively steer the coiled tubing drilling tool or other well string tool.

Abstract: An example method for estimating a time of flight (“TOF”) for an acoustic wave generated by an acoustic source for each of a plurality of acoustic receivers in an array can include recording data corresponding to the acoustic wave received at each of the acoustic receivers, estimating a respective TOF for the acoustic wave for each of the acoustic receivers, and discarding one or more of the respective estimated TOFs. Each of the discarded TOFs can be a statistical outlier. The method can also include calculating a plurality of time delays for the acoustic wave using a plurality of non-discarded estimated TOFs, and updating the respective estimated TOFs for the acoustic wave for each of the acoustic receivers using the calculated time delays. Each of the time delays can be a difference between respective estimated TOFs for the acoustic wave for at least two of the acoustic receivers.

Abstract: A computer-implemented method for determining elastic properties for a heterogeneous anisotropic geological formation is described herein. The method includes grouping sonic velocity data from a borehole section (or borehole sections) into a number of clusters (e.g., one or more clusters). The sonic velocity data is grouped into clusters using petrophysical log data from the borehole section. The method also includes inverting the sonic velocity data for the clusters to determine elastic properties for each cluster. In some cases, the elastic properties for the clusters are combined to determine a relationship between the elastic properties and formation heterogeneity.

Abstract: Systems, methods, and apparatus to drive reactive loads are disclosed. An example apparatus to drive a reactive load includes a reactive component in circuit with the reactive load, a first switching element in circuit with the reactive load to selectively hold the reactive load in a first energy state and to selectively allow the reactive load to change from the first energy state to a second energy state, a second switching element in circuit with the reactive load to selectively hold the reactive load in the second energy state and to selectively allow the reactive load to change from the second energy state to the first energy state, and a controller to detect a current in the reactive load, and to control the first and second switching elements to hold the reactive load in the first or the second energy state when the current traverses a threshold.

Abstract: A method for processing sonic data measured with a downhole tool is provided. The method comprises acquiring dipole wave data measured by a dipole acquisition in multiple firing, and estimating at least one of formation anisotropy properties based on the multiple firing dipole data. The at least one of formation anisotropy properties may be derived by Alford rotation processing. The method may further comprise processing with inversion of an orthogonality error angle of the firing data in two dipole firings and/or providing a quality control with the estimating result based on sonic measurements in a pump-off period.

Abstract: A method for estimating formation slowness is provided. The method comprises forward modeling to compute formation slownesses based on a first method for orthorhombic media using stress magnitudes and third-order elastic constants as inputs, and forward modeling to determine formation slownesses analytically based on a second method using stress magnitudes, stress azimuth and third-order elastic constants as inputs. The first method may be based on Tsvankin method and the second method may be based on Christoffel method. The forward modeling may further use well configuration and reference moduli as inputs, and the results from the forward modeling may include formation slownesses, and at least one of vertical slownesses, anisotropic parameters, anellipticity indicators and fast shear azimuth. The method may further comprise assessing quality of the forward modeling based on results output from the forward modeling.

Abstract: A downhole monitoring system and method that includes a sensor system with a sensor array with a number of sensors and a hub. Data measured by the sensors is processed by the hub and wirelessly communicated to a smart node. The sensor system may be mounted in the annulus formed between a borehole wall and an exterior surface of a well casing. The sensors may be configured to monitor the formation for microseismic events generated during hydraulic fracturing. The fracture growth and propagation may be monitored using the data obtained by the sensors. The data may facilitate real time control of the hydraulic fracturing operation.

Abstract: An example method for automatically characterizing an echo contained in an ultrasonic signal generated with an ultrasonic transducer can include receiving data corresponding to the ultrasonic signal, calculating an energy ratio of the ultrasonic signal and localizing the echo using the energy ratio. The method can include windowing a portion of the ultrasonic signal around the localized echo and calculating a Fast Fourier Transform (FFT) and a Hilbert envelop of the windowed portion. The method can include estimating M echo parameters from the FFT and the Hilbert envelope of the windowed portion, where each of the M parameter vectors includes a plurality of echo parameters, calculating M parametric echo models based on each of the M echo parameter vectors and iteratively minimizing a difference between the windowed portion of the ultrasonic signal and a sum of the M parametric echo models.

Abstract: A technique facilitates the accumulation and analysis of data related to a subterranean formation. An arrangement of different types of sensors is mounted on a collar utilized in accumulating data on the subterranean formation. The sensors are operable in combination to improve the image quality of data obtained with respect to the subterranean formation. Certain applications utilize an arrangement of sensors comprising at least one of each of an electromagnetic sensor and an ultrasonic pulse-echo transducer. A stabilizer or stabilizers may be used to precisely orient and position the sensors within a wellbore.

Abstract: A technique facilitates acoustic measurement and analysis in a variety of acoustic applications. An acoustic source is provided with a housing, e.g. a cylindrical housing, and a motor located within the housing. A piston is driven by the motor. The acoustic source also is provided with a radiating plate mounted along the housing and exposed to an environment surrounding the housing. A fluid passage contains actuating fluid and extends between the piston and the radiating plate. The piston and the radiating plate are linked by the fluid passage such that reciprocation of the piston by the motor causes oscillation of the radiating plate to create an acoustic signal. In some applications, a plurality of radiating plates and/or a plurality of motors may be arranged to enable monopole, dipole, cross-dipole, and/or quadrupole measurements.

Abstract: Automatic detection and accurate time picking of weak events embedded in strong noise such as microseismicity induced by hydraulic fracturing is accomplished by: a noise reduction step to separate out the noise and estimate its spectrum; an events detection and confidence indicator step, in which a new statistical test is applied to detect which time windows contain coherent arrivals across components and sensors in the multicomponent array and to indicate the confidence in this detection; and a time-picking step to accurately estimate the time of onset of the arrivals detected above and measure the time delay across the array using a hybrid beamforming method incorporating the use of higher order statistics. In the context of hydraulic fracturing, this could enhance the coverage and mapping of the fractures while also enabling monitoring from the treatment well itself where there is usually much higher and spatially correlated noise.

Abstract: A borehole tool used in a borehole comprises a tool body, a plurality of arms connected to the tool body so as to be movable radially relative thereto between a closed position and an open position, and a plurality of pads with a totally rounded outer shape. Each of the pads is mounted on each movable portion of the arms so as to be rotatable about a radial axis relative to the tool body according to the arm movement between the closed position and the open position.

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: A computer-implemented method for determining elastic properties for a heterogeneous anisotropic geological formation is described herein. The method includes grouping sonic velocity data from a borehole section (or borehole sections) into a number of clusters (e.g., one or more clusters). The sonic velocity data is grouped into clusters using petrophysical log data from the borehole section. The method also includes inverting the sonic velocity data for the clusters to determine elastic properties for each cluster. In some cases, the elastic properties for the clusters are combined to determine a relationship between the elastic properties and formation heterogeneity.

Abstract: Systems, apparatuses and methods for neural network signal processing of microseismic events. A series of sensors are disposable in at least one first well positioned about a second well disposed in a subterranean formation. The series of sensors obtain a data signal measurement including noise events and microseismic acoustic emission events. A processor includes a first neural network. The processor may remove the noise events from the data signal measurement and determine with the first neural network an arrival time for each microseismic acoustic emission event. An interface can output the arrival time for each microseismic acoustic emission event.

Abstract: Methods and apparatus to filter acoustic waveforms in downhole environments are described. An example method involves receiving acoustic waveform data representing acoustic signals traversing at least a portion of a borehole adjacent a subterranean formation and performing a direct transform operation on the acoustic waveform data to generate wavelet map data. The wavelet map data comprises a time-frequency representation of the acoustic waveform data.