Abstract: An apparatus and method may operate to mount acoustic sensors, azimuthally offset from each other, to the exterior of a casing. After the casing and acoustic sensors are in the borehole, signals are provided to the acoustic sensors to cause the acoustic sensors to emit acoustic signals into the annulus around the casing. The method further includes detecting reflected compression waves, shear waves or a combination or conversion thereof at the acoustic sensors to generate a set of two]way travel times of the acoustic signals. The method can further include generating distance measurements of a distance between corresponding acoustic sensors and points on the borehole wall based on the two]way travel times, to determine a position of the casing within the borehole. The method can further include identifying fluids based on the two]way travel times. Additional apparatus, systems, and methods are disclosed.

Abstract: A system to monitor the retrieval of a well tool from a wellbore comprises a deployment member coupled to the well tool to retrievably insert the well tool in the wellbore. At least one first identification transducer is coupled to a top end of the well tool to transmit an identification signal during retrieval of the well tool. At least one second identification transducer is located at at least one axial location along a surface pressure control assembly to detect the identification signal. A controller is in data communication with the at least one second identification transducer to determine the position of the well tool relative to the pressure control assembly, and to output at least one command related to the position of the well tool relative to the pressure control assembly.

Abstract: Methods for evaluating cement bonding in a wellbore are provided. An example method for determining cement impedance includes generating one or more acoustic signals within a wellbore comprising a borehole fluid, a casing, and a cement layer. One or more reflections of the acoustic signals may be received from at least a portion of the wellbore, wherein each of the one or more reflections comprises an initial reflection portion and a resonance portion. At least one of the initial reflection portion and the resonance portion may be modified based, at least in part, on an attenuation response of the borehole fluid. An impedance of the cement layer may be determined by analyzing at least one of the modified initial reflection portion and the modified resonance portion.

Abstract: An acoustic transducer, such as a bender bar, having ferroelectric actuation elements that are designed to optimize a predetermined deflection mode shape. The acoustic transducers may include one or more rounded modally shaped actuation elements or weighted actuation elements. Modal shaping of the actuation elements allows for specific targeting of modes which most efficiently radiate acoustic energy.

Abstract: An example cement and casing evaluation tool includes an amplifier and a filter coupled an output of the amplifier. A transducer may be coupled to the output of the filter. A ringing reduction system may be coupled to at least one of the amplifier, the filter, and the transducer, wherein the ringing reduction system selectively dissipates energy from at least one of the amplifier, the filter, and the transducer in response to a control signal.

Abstract: An acoustic imaging tool, logging system and method are disclosed for producing high-resolution three-dimensional images. The imaging tool may include three separate arrangements of acoustic transducers: a circumferential set for wall inspection, internal transducers for fluid characterization within a chamber open to wellbore fluid, and forward-looking transducers located at the bottom end of the tool. Forward-looking transducers emit ultrasonic waves and receive reflections back when solid features are located under the tool. In some embodiments, Doppler effect calculations may be performed to produce forward-looking acoustic images. In other embodiments, an ambient acoustic energy illuminates the wellbore, and an acoustic lens set focuses reflected ultrasonic waves onto an acoustic imaging array of an ultrasonic camera.

Abstract: In some implementations, a method for validating an acoustic bond-log tool includes having a test fixture including a wellbore casing emulating tubing. An outer tubing emulates a well formation and forms a perimeter of an annulus surrounding the wellbore casing emulating tubing. The wellbore casing tubing is configured with a stepped outer surface emulating different wellbore casing sidewall thicknesses. A dividing structure is coupled in the axial direction to the outer surface of the wellbore casing emulating tubing and to the inner surface of the outer tubing to radially subdivide the annulus into a plurality of hermetically sealable sample sections. Each sample section contains a sample of a material having a known acoustic impedance. The acoustic bond-log tool is validated by comparing a bond-log tool measurement of the acoustic impedance of each sample in a particular sample section to the known acoustic impedance of the sample.

Abstract: Disclosed herein is an approach to improving the accuracy of signal-peak tracking in acoustic logs by supplementing a semblance method used to detect signal peaks in individual coherence-, correlation- or amplitude-based semblance maps with consistency checks based on rock-physics constraints and/or based on history and/or future data for the signal of interest.

Abstract: A system and method for effective estimation of properties of a formation using acoustic array processing is disclosed. An acoustic tool is directed to a zone of interest in the formation and generates a first signal. Real data corresponding to the first signal is then received. One or more basic parameters are provided as input. The basic parameters may include parameters relating to the acoustic tool or parameters relating to the zone of interest. A time semblance shear slowness and a frequency semblance shear slowness are determined using the basic parameters. A mask is then selected using the determined time semblance and frequency semblance shear slowness values and used to isolate a dispersion curve. A shear slowness value is selected from the dispersion curve and quality control is performed on the selected shear slowness value.

Abstract: Disclosed herein is an approach to improving the accuracy of signal-peak tracking in acoustic logs by supplementing a semblance method used to detect signal peaks in individual coherence-, correlation- or amplitude-based semblance maps with consistency checks based on rock-physics constraints and/or based on history and/or future data for the signal of interest.

Abstract: A system and downhole tool comprising an ultrasonic transducer with a piezoelectric material embedded in a backing and a method of determining a parameter using the ultrasonic transducer. A self-noise of the transducer can be reduced by the piezoelectric material being at least partially embedded in the backing. The ultrasonic transducer can include an encapsulating material that encapsulates the backing.

Abstract: An example method includes determining a frequency response of a tuned pulse to be transmitted from a transmission element. A matching frequency envelope corresponding to a frequency envelope of the frequency response may be determined. A time domain signal corresponding to the matching frequency envelope may be determined. A series of digital pulses corresponding to the time domain signal may be determined. An analog output at a switching amplifier corresponding to the series of digital pulses may be generated. A transmission element may be excited with the analog output.

Abstract: A communication system that is positionable in a wellbore can include a first transceiver positioned externally to a casing string. The first transceiver can be operable to detect a presence or an absence of a surface wave; determine a location of a fluid in the wellbore based on the presence or the absence of the surface wave; and transmit data indicative of the location to a second transceiver. The surface wave can include an electromagnetic wave that has a magnetic field or an electric field that is non-transverse to a direction of propagation of the surface wave. The communication system can also include the second transceiver, which can be positioned externally the casing string and operable to receive the data.

Abstract: An assembly for use in a wellbore can include a plurality of sensors positioned external to a casing string. The plurality of sensors can be positioned for detecting an amount of a hydrocarbon that is present in a fluid in the wellbore and a pH of the fluid in the wellbore. The plurality of sensors can be positioned for wirelessly transmitting signals representing the amount of the hydrocarbon that is present in the fluid and the pH of the fluid to a receiving device.

Abstract: An example casing and cement evaluation tool may include a tool body and a rotating portion coupled to the tool body. A first transducer may be coupled to the rotating portion at a radial offset from a longitudinal axis of the tool. A second transducer may be coupled to the rotating portion at a different radial offset from the longitudinal axis of the tool.

Abstract: An example method includes determining a frequency response of a tuned pulse to be transmitted from a transmission element. A matching frequency envelope corresponding to a frequency envelope of the frequency response may be determined. A time domain signal corresponding to the matching frequency envelope may be determined. A series of digital pulses corresponding to the time domain signal may be determined. An analog output at a switching amplifier corresponding to the series of digital pulses may be generated. A transmission element may be excited with the analog output.

Abstract: In some embodiments, an apparatus and a system, as well as a method and an article, may operate to determine a compressional velocity (CV) of a geological formation, to determine a reflection coefficient (RC) associated with the geological formation, and to determine a density of the geological formation based on the CV and the RC. The CV and RC may be determined from values associated with sonic and ultrasonic velocity measurements. Additional apparatus, systems, and methods are described.

Abstract: A method of servicing a wellbore, comprising placing a plurality of Micro-Electro-Mechanical System (MEMS) sensors in a wellbore composition, placing the wellbore composition in the wellbore, obtaining data from the MEMS sensors using a plurality of data interrogation units spaced along a length of the wellbore, and telemetrically transmitting the data from an interior of the wellbore to an exterior of the wellbore using a conduit positioned in the wellbore. A system, comprising a wellbore extending the earth's surface, a conduit positioned in the wellbore, a wellbore composition positioned in the wellbore, the wellbore composition comprising a plurality of Micro-Electro-Mechanical System (MEMS) sensors, and a plurality of data interrogation units spaced along a length of the wellbore and adapted to obtain data from the MEMS sensors and telemetrically transmit the data from an interior of the wellbore to an entrance of the wellbore via the conduit.

Abstract: Systems and methods of determining settlement characteristics of a drilling mud are disclosed. Conditions under which heavier elements of the drilling mud settle under the influence of gravity can be determined. Samples of drilling mud can be placed in testing cells, and ultrasonic test pulses can be transmitted through the samples. Responses to the test pulses can be detected and compared to other responses detected at different vertical positions within the testing cell. Settlement can be detected when the responses from different vertical positions are generally dissimilar. An environmental temperature of the testing cell can be changed over a testing time interval, and a settlement temperature can be determined by detecting a divergence in the responses from different vertical positions.

Abstract: Systems, methods, and computer-readable storage devices for determining a location of an acoustic source outside of a borehole. The method relates to indicating a radial distance to the borehole, an offset along the borehole, and an azimuthal position around the borehole, of the acoustic source. The method includes receiving acoustic signals from respective acoustic sensors spaced along a tool lowered within the borehole. Using the acoustic signals and a borehole model, stacked energies are calculated for different radial distances from the borehole. At least one of the stacked energies is translated to an indication of a radial distance of the acoustic source from the borehole. The stacked energy for a radial distance is computed by offsetting the acoustic data signals in time in accordance the borehole model, summing the offset acoustic data signals to produce a stacked signal, and evaluating energy of the stacked signal over a time window.