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.

Waves from cement bond logging with a sonic logging-while-drilling tool (LWD-CBL) are often contaminated with tool waves and may yield biased CBL amplitudes. The disclosed LWD-CBL wave processing corrects the first echo amplitudes of LWD-CBL before calculating the BI. The LWD-CBL wave processing calculates a tool wave amplitude and a phase angle difference as the difference of the phases between the tool waves and casing waves. The tool waves are then used to correct the LWD-CBL casing wave amplitude and remove errors introduced from tool waves. In conjunction with the sets of operations described, the LWD-CBL wave processing also include array preprocessing operations. Array preprocessing may employ variation of bandpass filtering and frequency-wavenumber (F-K) filtering operations to suppress tool wave.

Downhole measurement systems and methods include deploying a bottomhole assembly having a multipole transmitter into a formation and transmitting acoustic signals into the formation. The multipole transmitter is of order n ≥ 2. Acoustic signals are received at respective receivers that are circumferentially aligned with the multipole transmitter, and are axially offset from the multipole transmitter, and axially offset from each other. The order of the first and second multipole receivers are equal to the order of the multipole transmitter. A controller is used to obtain first and second acoustic multipole data from the first and second multipole receivers at one or more azimuthal angles of a rotation of the bottomhole assembly in a formation during a drilling operation. Acoustic azimuthal anisotropy of the formation is determined from the first acoustic multipole data and the second acoustic multipole data.

Methods and systems for determining a drilling-induced rock damage map are disclosed. The method includes obtaining a sonic dataset, including sonic waveforms recorded at a plurality of source-receiver separations for a plurality of source positions along an axis of a wellbore. The method further includes determining a log of a first metric using the sonic dataset and determining a map of a second metric using the sonic dataset. The method still further includes determining the drilling-induced rock damage map based, at least in part, on the log of the first metric and the map of the second metric.

A method for processing seismic data may include receiving, via a processor, the seismic data acquired via a seismic survey. The seismic survey may include seismic sources that emit seismic wavefields at different locations. Each of the seismic sources may change a directivity pattern of a respective seismic wavefield based on a respective location of the respective seismic source. The seismic survey may also include seismic receivers that may receive the seismic data. The method may also include generating one or more basis functions that correspond to measurements of the seismic data, modelling a signal component of the seismic data as a sum of the one or more basis functions, and storing the signal component in a storage component. The signal component may be used to acquire an image of a subsurface region of the earth for identifying a feature in the subsurface region of the earth.

An acoustic logging method includes obtaining first horizontal transverse isotropy (“HTI”) angles resulting from a time domain HTI algorithm. The method further includes obtaining one or more second HTI angles resulting from a frequency domain HTI algorithm. The method further includes generating a first HTI anisotropy log including a relative angle log based on the first and second HTI angles. The method further includes generating a first color map of the first HTI anisotropy log and displaying the first color map.

An example method for displaying sonic logging data associated with a formation surrounding a borehole can include acquiring sonic data at a plurality of depths using an acoustic array located in the borehole and transforming the acquired sonic data from a time-space domain to a frequency-wave number domain at a limited number of discrete frequencies. The method can also include estimating slowness values at the limited number of discrete frequencies from the transformed sonic data, interpolating the estimated slowness values to obtain a projection of one or more slowness-frequency dispersions of the acquired sonic data and displaying the projection of the slowness-frequency dispersions. The projection of the slowness-frequency dispersions can include a plurality of color bands corresponding to each of the limited number of discrete frequencies.

A method for displaying slowness data after defects of anisotropy and heterogeneity have been removed includes visually depicting a slowness image on a computer monitor in which the slowness image includes a log of slowness values at a plurality of depths of a wellbore and a plurality of azimuth angles about a periphery of the wellbore. The image is processed via filtering such as with a bandpass filter. The filter may be obtained via fitting a periodic function to the slowness values at each depth or via a selected periodicity value and center angle. A resultant image is displayed.

Disclosed are systems and methods for high precision acoustic logging processing for compressional and shear slowness. The method comprises measuring, by a sonic logging tool, sonic data associated with a formation within a borehole, attempting a detection of a first arrival within the sonic data determining whether the attempted detection of the first arrival is accurate, and in response to an accurate detection of the first arrival determining a travel time of the first arrival, generating a coherence map including the first arrival, and determining, based on the coherence map, a characteristic of the formation.

To generate dispersion curves for acoustic waves in a radially layered system, a matrix M containing solutions to the wave equation subject to the boundary conditions of the system is constructed. The reciprocal condition number (RCN) of the matrix M is determined as a function of acoustic wave frequency and slowness. The local minima of the RCN in the frequency-slowness plane produces the dispersion curves corresponding to allowable acoustic modes in the system. A sensitivity analysis which identifies the dispersion curves dependent on a selected parameter. The dispersion curves independent of the perturbed parameters are eliminated by perturbing the modeling parameters and generating the RCN of the perturbed matrix M and then subtracting the RCN values of the unperturbed matrix M, leaving the dispersion curves that exhibit dependence on the selected parameter.