A method for identifying a material behind a pipe string. The method may comprise disposing an acoustic logging tool into a wellbore, insonifying a pipe string within the wellbore with the acoustic logging tool, recording sonic or ultrasonic data. The method may further comprise inputting the sonic or ultrasonic data into trained a machine learning model and identifying the material behind the pipe string using the trained machine learning model.

An inline source can be used for a marine survey. For example, a marine survey vessel can tow source units in line. The source units can be actuated near-continuously to cause a respective signal emitted by each of the source units to be uncorrelated with signals emitted by other of the source units.

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 data seismic sensing system and method for obtaining seismic refraction data and tomography data. The system may comprise a subsurface sensor array, wherein the subsurface sensor array is a fiber optic cable disposed near a wellbore, a seismic source, wherein the seismic source is a truck-mounted seismic vibrator comprising a base plate, and a surface sensor array, wherein the surface sensor array is coupled to the seismic source. The method may comprise disposing a surface sensor array on a surface, disposing a subsurface sensor array into a wellbore, activating a seismic source, wherein the seismic source is configured to create a seismic wave, recording a reflected seismic wave with the surface sensor array and the subsurface sensor array, and creating a seismic refraction data and a seismic tomography data from the reflected seismic 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 for processing seismic data acquired with non-impulsive moving sources are provided. Some methods remove cross-talk noise from the seismic data using emitted signal data and an underground formation's response estimate, which may be iteratively enhanced. Some methods perform resampling before a spatial or a spatio-temporal inversion. Some methods compensate for source's motion during the inversion, and/or are usable for multiple independently moving sources.

A method of performing measurements of an earth formation includes disposing at least a first receiver and a second receiver in one or more monitoring boreholes in a formation, and injecting fluid into the formation from an injection borehole, wherein injecting includes operating a fluid control device to generate seismic and/or acoustic noise having an identifiable characteristic. The method also includes detecting seismic and/or acoustic signals at the first receiver and detecting seismic and/or acoustic signals at a second receiver, the seismic and/or acoustic signals corresponding to the seismic and/or acoustic noise, calculating an estimate of a Green's function between the first receiver and the second receiver by processing seismic and/or acoustic waves detected by the first receiver and the second receiver to at least partially reconstruct the Green's function, and estimating variations in a velocity of a region of the formation by determining variations in the reconstructed Green's function.

Disclosed are control systems for marine vibrators. An example method may comprise recording a signal at a seismic sensor; running an iterative learning control characterization for a marine vibrator on the signal from the seismic sensor; measuring movement of an outer shell of the marine vibrator using a motion sensor to obtain a motion sensor signal; and controlling the marine vibrator using the motion sensor signal as a reference signal.

Computing device, computer software and methods for generating sweep signals corresponding to plural sources that generate seismic waves. The method includes selecting a nominal sweep signal (S0); applying a perturbation (P) to the nominal sweep signal (S0); and calculating the sweep signals (Sn) by varying the perturbation (P), each sweep signal corresponding to a seismic source.

Imperfect separation at the higher frequencies has been observed and was eventually was tracked down to the poor GFE signal that is normally used in the inversion. The invention thus uses a “derived GFE” for each source, obtained by comparing the shot records and remove the differences, instead of the prior estimated GFE signal put out by the controller, thus accurately maximizing the separation of the data.