A method for estimating a borehole condition using a Stoneley measurement is provided. The method comprises recording acoustic waveforms obtained from one or more receivers, applying a time window to the acoustic waveforms to extract Stoneley components, computing energies of the Stoneley components within a frequency band, and obtaining at least one of borehole conditions based on the energies of Stoneley components.

A seismic observation device includes: a waveform acquisition unit that acquires waveform data for a predetermined period including an observation start time of a P wave; a delay time specifying unit that inputs the waveform data to a trained model and acquires, from the trained model, a delay time from the observation start time of the P wave to an observation start time of an S wave; and an observation time estimation unit that estimates the observation start time of the S wave based on the observation start time of the P wave and the delay time.

Disclosed are a method and apparatus for estimating S-wave velocities by learning well logs, whereby the method includes a model formation step of forming an S-wave estimation model to output S-wave velocities corresponding to measured depth when the well logs are input based on train data sets including train data having values of multiple factors included in the well logs, the values being arranged corresponding to measured depth, and label data having S-wave velocities corresponding to measured depth as answers, and an S-wave velocity estimation step of inputting unseen data having values of multiple factors included in well logs acquired from a well at which S-wave velocities are to be estimated, the values being arranged corresponding to measured depth, to the S-wave estimation model to estimate S-wave velocities corresponding to measured depth.

Methods of providing digital images of living tissue that may include: obtaining data of a propagating wavefield through living tissue; obtaining a reference digital image of the living tissue; selecting a holographic computational method of wavefield imaging; selecting a wavefield based on one or more parameters; calculating a sampling ratio by dividing a number of data samples in the data subset by a number of image samples in the data subset; decimating the data subset; generating a new digital image based on the selected holographic computational method of imaging, the decimated data subset, and parameters corresponding to the data subset; and determining a quantitative difference measure between the reference digital image and the new digital image based on the changing of one or more parameters selected from the group consisting of field sampling, imaging sampling, and image quality.

Systems, methods, and computer-readable media for the attenuation of interface waves using polarization filtering applied to recorded single component seismic data are disclosed. A second component for polarization filtering is created by determining interface waves from the recorded data single component seismic data. The second component seismic data may be generated using an interface waves propagation model (in frequency or time-frequency domain) or by differential normal move-out (NMO) interpolation. Polarization filtering may be applied to multicomponent seismic data formed from the recorded single component seismic data and the generated second component seismic data to attenuate interface noise.

Methods to estimate formation slowness from multi-borehole modes and multi-mode dispersion estimation systems are presented. The method includes obtaining waveform data of a plurality of waves traversing through a downhole formation, wherein each wave of the plurality of waves has a different threshold cutoff frequency, and performing a multimode dispersion analysis of the waveform data to generate a semblance map of the wave comprising the plurality of waves. The method also includes obtaining a slowness dispersion of a wave of the plurality of waves, and determining a formation type of the wave based on one or more properties of the plurality of waves. The method further includes determining an initial body wave slowness estimate of the wave, generating a modeling of the wave, and reducing a mismatch between the modeling of the wave and the slowness dispersion of the wave to improve the modeling of the wave.

An exemplary embodiment of the present invention provides an anisotropic medium for full transmission of obliquely incident elastic waves considering a longitudinal wave and a shear wave by using an anisotropic medium designed to fully transmit elastic waves in a desired mode when elastic waves are obliquely incident to a boundary of different media. The anisotropic medium for fully transmitting an obliquely incident elastic wave according to an exemplary embodiment of the present invention includes: an incident medium to which an incident elastic wave including a longitudinal wave and a shear wave, and being obliquely incident with a predetermined incidence angle, is incident and reflected; a transmission medium to which a transmitting elastic wave including a longitudinal wave and a shear wave is transmitted; and an anisotropic medium, installed between the incident medium and the transmission medium, for blocking reflection of a predetermined reflecting elastic wave as a predetermined full transmission condition is satisfied, and fully transmitting a transmitting elastic wave in a predetermined type of full transmission, wherein the full transmission condition includes a phase matching condition based on a wavenumber relationship of an eigenmode in the anisotropic medium, and a polarization matching condition based on a relationship between a polarization vector and an amplitude of the eigenmode.

A well system includes a fiber optic cable positionable downhole along a length of a wellbore. The well system also includes a reflectometer communicatively coupleable to the fiber optic cable. The reflectometer injects optical signals into the fiber optic cable and receives reflected optical signals from the fiber optic cable. Further, the reflectometer identifies strain detected in the reflected optical signals generated from seismic waves of a microseismic event. Additionally, the reflectometer identifies a focal mechanism of the microseismic event and velocities of the seismic waves. The reflectometer also determines a position of the microseismic event using the strain detected in the reflected optical signals, the focal mechanism of the microseismic event, and the velocities of the seismic waves.

Methods are provided for determining properties of an anisotropic formation (including both fast and slow formations) surrounding a borehole. A logging-while-drilling tool is provided that is moveable through the borehole. The logging-while drilling tool has at least one dipole acoustic source spaced from an array of receivers. During movement of the logging-while-drilling tool, the at least one dipole acoustic source is operated to excite a time-varying pressure field in the anisotropic formation surrounding the borehole. The array of receivers is used to measure waveforms arising from the time-varying pressure field in the anisotropic formation surrounding the borehole. The waveforms are processed to determine a parameter value that represents shear directionality of the anisotropic formation surrounding the borehole.

Methods are provided for determining properties of an anisotropic formation (including both fast and slow formations) surrounding a borehole. A logging-while-drilling tool is provided that is moveable through the borehole. The logging-while drilling tool has at least one dipole acoustic source spaced from an array of receivers. During movement of the logging-while-drilling tool, the at least one dipole acoustic source is operated to excite a time-varying pressure field in the anisotropic formation surrounding the borehole. The array of receivers is used to measure waveforms arising from the time-varying pressure field in the anisotropic formation surrounding the borehole. The waveforms are processed to determine a parameter value that represents shear directionality of the anisotropic formation surrounding the borehole.