Abstract: A method comprises positioning a receiver in a borehole and determining an offset acoustic waveform at a target point. The method includes generating a reverse time sequence waveform of the determined offset acoustic waveform and generating, by a transmitter, an acoustic pulse based on the reverse time sequence waveform. The method includes detecting, by the receiver, an acoustic response to the acoustic pulse.

Abstract: A transmitter for inground use controls a depth signal transmit power in relation to a data signal transmit power such that one reception range of the depth signal at least approximately matches another, different reception range of the data signal. A portable device can form a system with the transmitter in which the portable device scans a plurality of frequencies within at least one low frequency depth signal range to measure the electromagnetic noise at each one of the plurality of frequencies and identify at least one of the frequencies as a potential depth frequency for the transmitter. The portable device can include a dual mode filter having a rebar mode and a normal mode filter. The depth signal frequency is dynamically positionable in relation to low frequency noise.

Abstract: A method for imaging one or more dipping structures is provided. The method comprises providing a given velocity model, calculating travel time of a seismic wave using the velocity model, estimating coherency of event signals of array data that are time-corrected for a trial reflector, weighting a waveform sample corresponding to the travel time based on the coherency, and mapping the weighted waveform sample.

Abstract: A system may comprise a transmitter amplifier, a first isolation module, a first transducer, a first receiver, a second isolation module, a second transducer, wherein the second isolation module is connected to the second transducer, and a second receiver, wherein the second isolation module and the second transducer are connected to the second receiver. A method may comprise disposing a downhole tool into a wellbore, transmitting an excitation signal from the transmitter amplifier to the first transducer and the second transducer through the first isolation module and second isolation module, and creating a pressure pulse from the first transducer and the second transducer, sensing the echo with the first transducer and the second transducer, converting the echo into a received signal at the first transducer and the second transducer, and transmitting the received signal to the first receiver and the second receiver.

Abstract: A transmitter for inground use controls a depth signal transmit power in relation to a data signal transmit power such that one reception range of the depth signal at least approximately matches another, different reception range of the data signal. A portable device can form a system with the transmitter in which the portable device scans a plurality of frequencies within at least one low frequency depth signal range to measure the electromagnetic noise at each one of the plurality of frequencies and identify at least one of the frequencies as a potential depth frequency for the transmitter. The portable device can include a dual mode filter having a rebar mode and a normal mode filter. The depth signal frequency is dynamically positionable in relation to low frequency noise.

Abstract: Predicting downhole acoustic tool responses due to stress-induced anisotropy by performing at least the following: receiving a plurality of input data corresponding to at least one well site comprising a wellbore; constructing a three-dimensional geomechanical model based at least in part on the input data; creating at least one near field versus far field stress distribution that corresponds to the wellbore from the three-dimensional geomechanical model; creating, at least one near wellbore versus far-field velocity distribution using the at least one near field versus far field stress distribution; comparing the downhole acoustic tool response property that indicates a downhole acoustic tool's penetration depth for a subsurface geological formation with the near wellbore velocity fields; and flagging, where the downhole acoustic tool response property stays within the near-wellbore velocity field.

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: 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.

Abstract: An ultrasonic imaging method is provided. A wideband acoustic pulse is fired at a wall. A wideband response signal is received. The wideband response signal is processed to select an impedance measurement frequency. A wavelet having a characteristic frequency approximately equal to the impedance measurement frequency is fired. A wavelet response signal is received. A reflection coefficient is determined from the wavelet response signal. An impedance measurement is calculated from the reflection coefficient. Related tools and systems are also disclosed.

Abstract: A method and system adaptively reduce a peak-to-average power ratio in a communication system. Energy is clipped from at least one peak of a modulated signal. The modulated signal includes a plurality of sub-carriers. At least one data sub-carrier is adaptively selected for peak-to-average power ratio reduction use based on known scheduling information. The clipped energy is distributed among at least one data sub-carrier.

Abstract: Characterizing a reservoir with electromagnetic imaging surveys includes normalizing measured voltage data by transmitter moment, sorting the normalized voltage data into common receiver profiles, densely resampling transmitter locations using common positions for the receiver profiles, coarsely resampling the data at discreet transmitter locations, defining a starting model for inversion, weighting the data by a factor, converting the normalized voltage data to ratios, calculating a conductivity image using a ratio inversion method, and verifying that an inversion has converged and the image is geologically reasonable. The image can then be displayed. The invention can be used for cross-well, surface-to-borehole, borehole-to-surface, and single-well (borehole-to-borehole) measurements measurements by which the effects of steel casing are reduced.

Abstract: Measurements of impedance are made using a piezoelectric transducer oriented at different angles to a formation bedding plane. The impedance measurements are then used to estimate the anisotropic velocity of the formation.

Abstract: An ultrasonic imaging method is provided. A wideband acoustic pulse is fired at a wall. A wideband response signal is received. The wideband response signal is processed to select an impedance measurement frequency. A wavelet having a characteristic frequency approximately equal to the impedance measurement frequency is fired. A wavelet response signal is received. A reflection coefficient is determined from the wavelet response signal. An impedance measurement is calculated from the reflection coefficient. Related tools and systems are also disclosed.

Abstract: In some embodiments, an apparatus and a system, as well as a method and an article, may include generating attenuation values associated with a set of multiple signals received by multiple receivers from a transmitted signal as a function of reception time and material velocity. The attenuation values may be stored in a memory and/or displayed on a display, perhaps in conjunction with a semblance map.

Abstract: A wave generating device and method of using the same wherein the device is for producing a shear wave in a ground layer wherein the generated wave emanates from a bore hole in the ground layer and passes through the ground layer toward a receiver spaced from the bore hole. This wave having a given waveform and the bore hole being defined by at least one bore wall that extends from a surface of the ground layer to a bottom extent of the bore hole. The device including a driver having an outer layer extending in a longitudinal direction along a longitudinal axis and having a radially outwardly facing surface generally parallel to the longitudinal axis which is configured to engage an associated bore wall of an associated bore hole.

Abstract: There is a problem that a delay is caused in signal processing by exercising control so as to cause amplitude peaks in a transmission signal to fall in a prescribed range. A transmission apparatus for conducting wireless communication makes a decision whether a specific pattern which causes a peak exceeding a predetermined amplitude range to be generated in frequency characteristics of a transmission signal is included in a transmission code sequence for forming the transmission signal. And the transmission apparatus selects filter coefficients which prescribe a band limiting factor for the frequency characteristics of the transmission signal, on the basis of a result of the decision, and conducts filtering on the transmission code sequence by using the selected filter coefficients.

Abstract: Characterizing a reservoir with electromagnetic imaging surveys includes normalizing measured voltage data by transmitter moment, sorting the normalized voltage data into common receiver profiles, densely resampling transmitter locations using common positions for the receiver profiles, coarsely resampling the data at discreet transmitter locations, defining a starting model for inversion, weighting the data by a factor, converting the normalized voltage data to ratios, calculating a conductivity image using a ratio inversion method, and verifying that an inversion has converged and the image is geologically reasonable. The image can then be displayed. The invention can be used for cross-well, surface-to-borehole, and borehole-to-surface measurements by which the effects of steel casing are reduced.

Abstract: Methods and systems for taking measurements related to subterranean formations. The methods and systems provide robust, reliable first arrival data for component signals of interest, which may be used to estimate formation slowness, characterize formation slowness zones, or act as an input to other processes. The methods and systems are capable of automatically providing good first arrival data based on signals received without any human interaction, and without setting or changing any parameters.

Abstract: A method of determining the sonic slowness of a formation traversed by a borehole comprising generating tracks from sonic waveform peaks received at a plurality of depths wherein the peaks that are not classified prior to tracking is set forth. A method for generating a slowness versus depth log is generated for waveform arrivals by classifying long tracks, classifying small tracks; classifying tracks that overlap; filling in gaps; and creating a final log is disclosed. In further improvements, non-classified tracks and interpolation are used to fill in gaps.

Abstract: The invention provides techniques for calculating velocity from sonic signals with an improved signal to noise ratio, accuracy and certainty of result. Multichannel coherence measures are calculated from sonic transmitter signals and averaged to produce an average coherence measure. The formation slowness is determined from the averaged coherence measure.

Abstract: Methods for processing ultrasonic signal data to evaluate subsurface properties and tool orientation. Acoustic signals are transmitted into a plurality of azimuthal borehole positions. Formation echo signal transit time distributions are then determined in a plurality of azimuthal sectors for the acoustic signals. Front face echo signal transit times are also measured and farther-mode and closer-mode transit times are determined for the distribution of formation echo signals. Farther and closer tool standoffs are determined for the azimuthal sectors and a borehole diameter is determined from a summation including standoffs in opposing sectors. The standoffs are also used to determine a preferential tool position.

Abstract: The present invention provides an ink jet recording apparatus including a carriage to which a recording head for effecting recording on a recording material by discharging ink and an ink tank for containing ink to be supplied to the recording head are detachably mounted in a separate exchanging permitting manner and which shifts the recording head and the ink tank in a direction perpendicular to a conveying direction of the recording material, comprising an ink tank exchanging position which is a position of the carriage, where the ink tank is to be exchanged, and a recording head exchanging position which is different from the ink tank exchanging position and which is a position of the carriage where the recording head is to be exchanged.

Abstract: An improved technique for determining the thickness of a member, especially pipe such as fluid-filled casing in an earth borehole, includes the following steps: directing a pulse of ultrasonic energy toward the inner surface of the pipe, and receiving and storing, as a function of time, signals representative of ultrasonic energy reflected from the inner surface of the pipe; determining, from the stored signals, the arrival time of the initial echo from the inner surface; determining, from the stored signals, the arrival time and the amplitude of a first candidate initial echo from the outer surface of the pipe; performing a reverse search on the stored signals to determine, from stored signals at times earlier than the arrival time of the first candidate, the arrival time and the amplitude of a second candidate initial echo from the outer surface; comparing amplitudes of the first and second candidates, and selecting, based on the comparison, one of the first and second candidates as the actual outer surface

Abstract: A method is disclosed for inverting 3-D seismic reflection data obtained from seismic surveys to derive impedance models for a subsurface region, and for inversion of multiple 3-D seismic surveys (i.e., 4-D seismic surveys) of the same subsurface volume, separated in time to allow for dynamic fluid migration, such that small scale structure and regions of fluid and dynamic fluid flow within the subsurface volume being studied can be identified. The method allows for the mapping and quantification of available hydrocarbons within a reservoir and is thus useful for hydrocarbon prospecting and reservoir management. An iterative seismic inversion scheme constrained by actual well log data which uses a time/depth dependent seismic source function is employed to derive impedance models from 3-D and 4-D seismic datasets. The impedance values can be region grown to better isolate the low impedance hydrocarbon bearing regions.

Abstract: A method for transmitting ultrasonic amplitude and time travel information obtained from borehole logging operations over a logging cable allows accurate measurement of the time travel by surface equipment. The time travel information is transmitted by a time travel pulse, which is produced at a time interval from a synchronization pulse corresponding to the time of travel of an acoustic return. The peak amplitude of the acoustic return is transmitted by a separate amplitude pulse.

Abstract: In accordance with principles of the present invention methods and apparatus are provided for evaluating the quality of the cement bond in cased boreholes. Acoustic energy is used to excite the borehole-casing-annulus-formation system and the quality of the cement bond is determined by examining the ratios of the signals received by two longitudinally spaced apart receivers supported on a sonde. The acoustic energy is generated by two transmitters symmetrically disposed above and below the receivers along the sonde. The spacings between the receivers themselves and between the receivers and the transmitters are selected so as to enhance the correlation between the ratios of the received signals and the quality of the cement bond log. An additional receiver, supported on the sonde at a small distance from one of the transmitters, is employed to determine the quality of the cement bond in hard formations.

Abstract: A seismic marine survey is carried out by traversing a line of exploration with an acoustic energy source, an array of spaced-apart receivers, and a recording system. Seismic reflection signals recorded by the receivers are digitized to provide a plurality of digital data samples. A logarithmic value is determined for each digital data sample. These logarithmic values are plotted to provide a seismogram with the seismic reflection signals being recorded in side-by-side trace relationship.

Abstract: In connection with a borehole televiewer system (10), the delta time (51) between low threshold (54) crossing (T.sub.1) and signal peak arrival (T.sub.2) provides a measure of mudcake (43) thickness.

Abstract: A method and apparatus for processing a signal generated by a borehole scanning system of the type in which periodic electrical firing pulses initiate a plurality of corresponding acoustic energy pulses which are transmitted from the central portion of the borehole toward the borehole wall in a plurality of radial directions and at a plurality of different depths, thereby generating reflected acoustic pulses which are detected and converted to electrical pulses. The electrical pulse is periodically sampled with each sample level being converted to a digital number. Each new digital sample number is compared to the maximum of the preceding digital sample numbers and stored if the new digital sample number exceeds that maximum. A counter initiates counting in response to the firing pulse preceding the sample electrical pulse.

Abstract: A method and apparatus for determination of earth formation permeability in situ. A logging sonde supported in a borehole derives attenuation data from at least two ultrasonic energy transmission paths which have a common alignment but differing length, the attenuation data can then be used to determine an empirical X parameter that is directly related to formation permeability.

Abstract: In accordance with principles of the present invention methods and apparatus are provided for evaluating the quality of the cement bond in cased boreholes. Acoustic energy is used to excite the borehole-casing-annulus-formation system and the quality of the cement bond is determined by examining the ratios of the signals received by two longitudinally spaced apart receivers supported on a sonde. The acoustic energy is generated by two transmitters symmetrically disposed above and below the receivers along the sonde. The spacings between the receivers themselves and between the receivers and the transmitters are selected so as to enhance the correlation between the ratios of the received signals and the quality of the cement bond log. An additional receiver, supported on the sonde at a small distance from one of the transmitters, is employed to determine the quality of the cement bond in hard formations.

Abstract: Method and apparatus for measuring formation compressional and shear wave velocities characterized by a downhole tool having an attenuation chamber between a transmitter and a receiver and a plurality of receivers spaced from the transducer so as to discriminate through the amplitude of the reflected compressional wave the critical angles for the respective formation compressional and shear wave velocities, thereby determining the formation compressional and shear wave velocities. Also disclosed are preferred embodiments in which the plurality of connectors connected between the receivers are also connected with a recorder for recording gated time interval signals. A discriminator and gate are provided for discriminating the largest amplitude of received acoustic energy signals received during the gating period.

Abstract: For use in a downhole acoustic logging system including an acoustic transmitter and spaced acoustic receiver, the preferred and illustrated embodiment incorporates a gain control for the receiver system. The automatic gain control (AGC) controls data capture without clipping or fadeout, and provides the digitized value of gain setting to be recorded to assist in data reduction whereby the digitized signal and gain of the system are obtained. The inbound signal is divided into a pressure wave, a shear wave and a fluid wave. The gain function is divided into three gain control regions indentified hereinafeter as the P, S and F regions, and the gain is stepped automatically to provide an output voltage within specified limits. Those limits are observed, thereby operating the gain controlled in the AGC in digital fashion, and the received signal is amplified in a controlled manner, thereby enabling recordal of the wave form without clipping or fadeout while capturing the gain to enable recovery of the data.

Abstract: The invention relates to a method of seismic exploration by acoustic well logging.It is characterized in that in the traces recorded corresponding to each transmitter-receiver pair, each type of wave of interest is identified using the results of a velocity analysis, then the time of appearance in the trace of a characteristic event of the phase of the wave of interest is determined and the velocity of the wave is deduced from this time and from the thickness of the layer of formation studied.

Abstract: A method and apparatus for measuring an earth formation characteristic from inside a borehole penetrating earth formations is described. A tool carrying a sonic transmitter and an array of receivers is moved along the borehole and waveform signals from the receiver array are generated from repetetive operations of the transmitter. Sub-arrays of particularly related waveform signals relevant to a selected depth interval that is less in length than the aperture of the array are identified. Each sub-array of signals is then converted to a domain of signals composed of values of a coherence as a function of a range of values of a characteristic such as slowness. The converted signals are then combined so as to provide combined coherence values as a function of different values of the characteristic. One or several peaks of the combined coherence values are detected and determine the value of the characteristic for the selected depth interval. Similar processing is continued for other depth intervals.

Abstract: Acoustic signals are transmitted in a direction substantially perpendicular to the borehole axis, from different levels of at least three determined generatrices of the borehole wall. Reflected acoustic signals are received from the same direction at different levels of these generatrices. A train of signals is derived from each reflected acoustic signal and at least a group of significant elements of this signal train is selected. The groups of significant elements of the signals obtained for the different generatrices are correlated. The interval between signal trains corresponding to the maximum correlation corresponds to one and the same geological formation and is representative of the dip angle of this formation.

Abstract: In the injection of fluids into subsurface geological formations, such as for the purpose of recovering a mineral in that formation, it is important that the flow progress of that fluid is known at all points in the subsurface. This information is provided by injecting a selected fluid into the formation. This fluid may be a gas, or a liquid, or a mixture of gas and liquid. When this fluid is in the subsurface formation there will be a mixture of gas and liquid in selected proportion in the formation. This mixture in a geologic formation overlain by a shale, for example, will have a much higher reflection coefficient. A source of seismic waves is operated at the surface, and the received reflections are compared between spaced positions on the surface.

Abstract: An improved well logging technique is provided for more accurately deriving acoustic measurements of sub-surface earth formations. Method and apparatus are described for converting an acoustic signature which can be generated on a depth dependent or time dependent basis, into digital format and subsequently employing special processing techniques to yield parameters such as velocity of the transmitted acoustic energy through earth formations and the amplitude of the received acoustic energy. Processing further allows for the generation of noise immunity signals functionally related to a measured signature parameter and for the generation of amplitude control signals. Additionally, a control signal is generated to optimize transmitter firing rate.

Abstract: A well-logging method and apparatus in which a fast real time portion of a logging signal is sequentially sampled at discrete times. These sampled segments are stored and then are clocked out of storage over an expanded time period.The rms amplitude portion of the logging signal occurring prior to the compression wave part of the logging signal (the nominal noise level) may be used for AGC regulation of an amplifier which amplifies the time-expanded output.A similar development of an rms value can be used for establishing a threshold level for a peak detector, which level is set slightly higher than such rms value. The first three successive samples greater than the threshold level detected by the detector are presumed to be the first three samples of the compression wave. This presumed compression wave is recorded and convolved against the expanded-time digital form of the logging signal to locate the compression wave in a second received signal and, later, the similarly appearing "shear" wave.

Abstract: A method and apparatus are described for detecting an acoustic wave in a waveform produced from a sonic receiver in response to an acoustic investigation of a borehole. The maximum amplitude of the waveform is measured and a portion thereof utilized as a threshold for comparison with successively different combinations of initial portions of the waveform and the waveform location, where the threshold is exceeded, is identified as the location of the wave. A pattern comparison is made between waveform segments where the acoustic wave is initially located to provide a correction factor for a more accurate locating of the acoustic wave. A parameter of the wave, such as its interval travel time is measured with the acoustic wave locating techniques.