A method and system to be used in well inspection. An acoustic signal is transmitted from a well inspection tool into a well structure and one or more return signals is detected using at least one receiver. At least one processor is used to generate variable density log (VDL) data that includes multiple waveforms in a time domain from the one or more return signals. A number of independent components to be used based on variances in the VDL data is determined and the multiple waveforms are decomposed into multiple components associated with one or more local structure variances of the well structure using independent component analysis (ICA) and the number of independent components. Characteristics of the well structure is determined based in part on patterns or features associated with one or more independent components from the multiple components.

Methods for measuring seismic velocities and for monitoring local changes in inter-well seismic velocities in real time are described. Two or more spaced-apart observation wells are provided. Seismic receiver arrays are placed in the observation wells, and a seismic source array is provided at surface locations away from the well bores and producing areas. Compression (P), vertical shear (Sv) and/or horizontal shear (Sh) seismic wave signals are generated from each element of the seismic source array, and the seismic signals arriving at the receivers in the observation wells are recorded. The virtual source method is then applied to the recorded data to compute emulated cross-well seismic signals of the virtual sources at receiver locations in one observation well propagating toward the receivers at other observation wells. Analysis of direct arrivals of emulated cross-well seismic signals can be completed to extract travel times, inter-well seismic velocities, and rock properties.

A well tool can be used in a wellbore that can measure characteristics of an object in the wellbore. The well tool includes an ultrasonic transducer for generating an ultrasonic wave in a medium of the wellbore. The ultrasonic transducer includes a front layer, a rear layer, backing material coupled to the rear layer, and piezoelectric material coupled to the front layer and to the backing material. The rear layer can improve signal-to-noise ratio of the transducer in applications such as imaging and caliper applications.

Multicomponent data are acquired using a downhole acoustic tool having transmitters and receiver stations distributed azimuthally in a plane perpendicular to the axis of the tool. The receiver stations are located at several receiving stations along the axis of the tool. At each acquisition depth, waveforms are processed through a multi-dimensional fast Fourier transform, extrapolation and inverse multi-dimensional fast Fourier transform. At each receiver station, waveforms are combined to produce the standard monopole waveforms and the inline and crossline dipole waveforms along fixed azimuths. These oriented waveforms produce a finer azimuthal sampling of the surrounding formation, and can then be used for imaging geological features within the surrounding formation.

An apparatus for detecting a location of an optical fiber having an acoustic sensor disposed subsurface to the earth includes an acoustic emitter configured to emit a first signal having a first frequency and a second signal having a second frequency that is higher than the first frequency, the first and second emitted acoustic signals being azimuthally rotated around the borehole and an optical interrogator configured to interrogate the optical fiber to receive an acoustic measurement that provides a corresponding first received signal and a corresponding second received signal. The apparatus also includes a processor configured to (i) frequency-multiply the first received signal to provide a third signal having a third frequency within a selected range of the second frequency, (ii) estimate a phase difference between the second received signal and the third signal, and (iii) correlate the phase difference to the location of the optical fiber.

A sonic logging method is provided that transmits acoustic signals using a high order acoustic source and processes waveform data to identify a set of arrival events and time picks by automatic and/or manual methods. Ray tracing inversion is carried out for each arrival event over a number of possible raypath types that include at least one polarized shear raypath type to determine two-dimensional reflector positions and predicted inclination angles of the arrival event for the possible raypath types. One or more three-dimensional slowness-time coherence representations are generated for the arrival event and raypath type(s) and evaluated to determine azimuth, orientation and raypath type of a corresponding reflector. The method outputs a three-dimensional position and orientation for at least one reflector. The information derived from the method can be conveyed in various displays and plots and structured formats for reservoir understanding and also output for use in reservoir analysis and other applications.

Deconvolution-based processing of ultrasonic waveforms enables robust calculation of two-way travel time for an ultrasonic caliper, particularly in the presence of multiple, proximal reflectors (e.g., mud cake, formation, casing, cement, etc.).

The present invention is related to a method for reconstructing at least one trace in a seismic image of a common receiver and time domain, the image comprising traces in time domain with seismic data and one or more traces to be reconstructed. A first aspect of the invention is a method that is characterized by a specific use of a convolutional neural network trained under an unsupervised learning approach with a modified receptive field. A second aspect of the invention is a deblending method based on the use of a reconstructing method according to the first aspect of the invention applied to a denoising step of a deblending process allowing a very effective data acquisition while keeping a high quality output data sets after being processed according to the first and/or second aspects of the invention.

A method for determining microseismic events. The method may include measuring a seismic travel time of a microseismic event with a fiber optic line disposed in a first wellbore, forming a probability density function for the microseismic event based at least in part on the seismic travel time measurement, modifying the probability density function by applying one or more constraints to form a modified probability density function, identifying one or more most probable source locations from the modified probability density function, and forming a microseismic event cloud from the one or more most probable source locations.

Methods to estimate formation shear wave slowness from multi-firings of different types of acoustic sources and multi-mode dispersion estimation systems are presented. The method includes obtaining waveform data of waves traversing through a downhole formation, where the waves are generated from multi-firings of different types of acoustic sources. The method also includes performing a multimode dispersion analysis of the waveform data for each firing of the multi-firings, and removing one or more tool waves generated from the multi-firings. The method further includes determining a formation type of the formation the waves traverse based properties of the waves and determining an initial shear wave slowness estimate of the waves. The method further includes generating a modeling of the waves, and reducing a mismatch between the modeling of the waves and a slowness dispersion of the waves to improve the modeling of the waves.