Abstract: Methods and apparatuses for seismic exploration of an underground structure obtain improved images by integrating partial match filtering in an FWI. Filtered (auxiliary) data replaces one of the observed data and the synthetic data in the FWI's objective function to avoid cycle skipping.

Abstract: The present invention relates to a method for estimating a pattern, in particular a pitch and/or a fundamental frequency, in a signal having a periodic, quasiperiodic or virtually periodic component, wherein the signal is transformed from a time-domain to a frequency-domain to obtain a spectrum of the signal, the spectrum is processed to obtain a zero-phase spectrum of the signal, the spectrum of the signal is transformed to the time-domain to obtain a correlation signal, the spectrum and the correlation signals are combined to a combined spectrum, and the pattern is estimated on the basis of the combined spectrum.

Abstract: In an embodiment a semiconductor device correlates a received signal with a known pattern. A correlation output is used as a basis for forming a confidence reference level. The confidence reference level and the correlation output are compared to identify a peak in the received signal indicating that a present signal state of the received signal contains the known pattern.

Abstract: A method and apparatus for profiling and identifying the source of a signal is provided. A first method includes receiving a signal produced by a known source and creating a matrix of wavelet coefficients corresponding to a wavelet transform of the signal. The method also includes profiling the signal according to an output of a wavelet transform utilizing a particular base function and a particular scale set. A second method includes performing a wavelet transform having a particular profile on a received signal and determining the presence of a particular signal-producing entity as a function of wavelet coefficients exceeding a threshold. An apparatus includes a receiver configured to receive a signal and a processor coupled to the receiver, such that the processor is configured to perform wavelet transforms on the signals. A database is coupled to the processor and configured to store wavelet transform profiles.

Abstract: Methods and apparatus are provided related to seismic sensor data. Seismic sensor signaling is digitally sampled in accordance with a local clock and without synchronization to standardized time. Timestamp data is used to synthesize data correspondent to an artificial stimulus waveform. Cross-correlation of the synthesized data with the seismic sensor data yields a correlation result. The correlation result can be scaled to an original starting time for the seismic data sampling. The scaled correlation result can be stored in computer-accessible media and subject to further processing or interpretation.

Abstract: Method for separating signals recorded by a seismic receiver and generated with at least two vibratory seismic sources driven with no listening time. The method includes receiving seismic data that includes data d recorded by the seismic receiver and data related to the first and second vibratory seismic sources; computing a source separation matrix based on the data related to the first and second vibratory seismic sources; calculating first and second earth impulse responses HA and HB corresponding to the two vibratory seismic sources, respectively, based on the data d recorded by the seismic receiver, the data related to the two vibratory seismic sources and the source separation matrix; and separating the signals recorded by the seismic receiver based on the first and second earth impulse responses HA and HB such that signals the two vibratory seismic sources are disentangled.

Abstract: A method and device for monitoring a subsoil zone, wherein a plurality of receivers are arranged on a surface of the soil or near said surface, straight above a geological zone to be monitored, comprising the following steps: generating a set of reference seismic data; recording seismic data by means of said receivers; correlating the seismic data recorded with the reference seismic data; comparing each trace of the correlated data, with correlated traces located in a vicinity of said trace, in order to evaluate a similarity of each correlated trace with the adjacent correlated traces; and, detecting a microseismic event occurring in the subsoil zone by analysing said similarity. The method and device enables real-time monitoring.

Abstract: A method of identifying passive seismic events in seismic data that contains at least first seismic data traces acquired at a first seismic receiver and second seismic data traces acquired at a second receiver spatially separated from the first receiver comprises determining an overall measure of similarity for a pair of events in the seismic traces. The overall measure of similarity is indicative of similarity between the events acquired at the first seismic receiver and of similarity between the events acquired at the second seismic receiver. In one method, the overall measure of similarity is an overall cross-correlation coefficient. The overall cross-correlation coefficient is found by determining a first correlation coefficient for the pair of events from the data acquired at the first receiver and determining a second correlation coefficient for the pair of events from the data acquired at the second receiver.

Abstract: A method of processing seismic data obtained using a seismic vibrator that includes estimating travel times of direct wave arrivals between the seismic vibrator and an array of seismic receiver locations and wavefield deconvolving the seismic data using the direct wave arrival travel times. Also a related method of producing a high-frequency geological subsurface image that includes acquiring seismic data having significant harmonic energy using a seismic vibrator, estimating direct wave arrival travel times between the seismic vibrator and an array of seismic receiver locations, wavefield deconvolving the seismic data using the estimated direct wave arrival travel times, and using the wavefield deconvolved seismic data to produce a high-frequency geological subsurface image. A further related computer useable medium having computer readable program code means embodied therein practicing the inventive method.

Abstract: The present invention provides a method for harmonic noise attenuation in correlated sweep data in seismic exploration. The method includes forming a plurality of correlation data subsets using a plurality of sweep data sets and a correlation reference sequence. The method further includes estimating a noise level in a correlation data set using the correlation data subsets and subtracting the estimated noise level from the correlation data set.

Abstract: Methods and systems are provided for acquiring seismic data. Data are collected representing acoustic signals received from the Earth at distinct geographic locations. Data representing an ambient signal at the distinct geographic locations are also collected. For each of the geographic locations, a known time dependence of the ambient signal is correlated with a time dependence of the collected acoustic-signal data to define time-correlated acoustic signal data. The collected acoustic-signal data for the distinct geographic locations are synchronized from the time-correlated acoustic-signal data.

Abstract: This invention relates to improved methods to generate shaped sweeps, and for the acquisition of vibroseis data with a shaped pilot sweep.

Abstract: A method for tomographic modeling of seismic wave travel times from well drilling records generated by drill string vibrations during drilling and identifying in the recorded vibration at least one of direct, reflected, refracted, converted and diving waves so as to measure wave velocity in near surface layers.

Abstract: A method of calculating a throw volume corresponding to a seismic data volume. A range of time shifts and a search direction for the seismic data volume are selected. A data location separation and a vertical time window are also selected. A cross-correlation is calculated between data values corresponding to first and second data locations separated by the data location separation and symmetrically located in the search direction on each side of a target data location. The cross-correlation is calculated throughout the vertical time window for each time shift in the range of time shifts. The time shift corresponding to the maximum calculated cross-correlation is stored in the throw volume.

Abstract: Methods and systems are provided for acquiring seismic data. Data are collected representing acoustic signals received from the Earth at distinct geographic locations. Data representing an ambient signal at the distinct geographic locations are also collected. For each of the geographic locations, a known time dependence of the ambient signal is correlated with a time dependence of the collected acoustic-signal data to define time-correlated acoustic signal data. The collected acoustic-signal data for the distinct geographic locations are synchronized from the time-correlated acoustic-signal data.

Abstract: This invention relates to mapping the hydrocarbon reservoir characteristics by mapping the reservoir formations that display dynamic elastic nonlinearity responses to the seismic signals. The main reason of this nonlinear behavior in the reservoir rocks is their bulk rock property: the porosity, fractures, differential pressure and pore saturation. To map these bulk rock properties, the interaction of the two seismic waves as they propagate through elastically nonlinear rocks is recorded. Two compressional seismic signals are transmitted from the surface. Seismic reflection data using surface or borehole detectors are recorded. One of the transmitted signals is a conventional swept frequency and the other is a mono-frequency signal. During the propagation of these two signals through the elastically nonlinear reservoir rocks, there is an interaction between the two signals. The sum and difference frequencies of the two primary seismic signals that were transmitted from the surface are created.

Abstract: Excellent likeness of impulse response function r.sub.o (t) of a given linear space is obtained by exciting the space through a transmitting transducer with a compressible probing signal x(t) which is a string of lowpass narrow p(t)-wavelets polarity-controlled by a single cycle of an m-sequence and processing received raw-data by cross-correlating it with a special reference s(t) which is cyclical repetition of the same m-sequence. Cross-correlating x(t) directly with s(t) yields compressed version of x(t) (denoted e(t)) which is p(t) multiplied by length of the m-sequence. e(t) equivalently excites the space to give processed output which is the likeness of r.sub.o (t). e(t) is free from side-lobes and readily made arbitrarily slim by choosing p(t) slim; keeping duration and energy of x(t) fixed, e(t) characterizes an area invariant of the slimness of e(t) or p(t).

Abstract: A method for producing simple seismic wavelet shapes with minimal side lobe energy for use as reference signals for seismic vibrators is disclosed.

Abstract: Seismic data is cross correlated with a correlation reference which is an amplitude modified version of a nonlinear sweep. The amplitude modification provides both deboost and tapering.

Abstract: A seismic processing apparatus comprises a plurality of processing modules (12), each module comprising a transputer (T) and a transversal filter (TF) with these transputers of the modules connected in a linear array by their links. The apparatus is able to carry out real-time demultiplexing of the seismic data from a plurality of receiver channels, and is able to carry out a number of other processing functions in the field, e.g. common depth point stacking, summing, correlation, convolution and two dimensional Fourier transforms.

Abstract: A method for removing noise from seismic wiggle traces is provided. Data points from the seismic traces are selected for which amplitude and derivative values are determined. The derivative values are crossplotted as a function of the amplitude values. A rejection line is then selected on the crossplot wherein all data points which plot outside of the rejection line are treated as noise, such data points being assigned a new amplitude value to thereby remove the noise from the seismic traces.

Abstract: In seismic profiling systems utilizing sweeps of signals which change in repetition frequency during the transmission interval, interference results from a spurious correlation against an interfering sweep, usually produced by the first break reflection of a simultaneously transmitted sweep which is in the opposite sense for 3-D surveying or from another source. The first break interfering sweep repeats while correlating with time slipped replicas in surveying for deeper and deeper reflecting interfaces and appears as correlation sidelobe interference which has a significant contribution to the correlator output only when the interfering sweep and the replica are in a condition where their frequencies are identical or nearly so. This condition is known as stationary phase.

Abstract: The system for suppressing an ambient noise signal which comtaminates a desired signal includes a noise pickup detector for detecting the ambient noise signal. A noise discriminator processes the detected noise signal into noise data. A reference noise generator converts the noise data into a reference noise signal. The noise generator automatically adjusts the reference noise signal to correspond with changes in the noise signal as it is being detected. A filter filters the reference noise signal into an error signal which is adapted to remove the noise signal from the contaminated signal. A cross-correlator cross-correlates the contaminated signal with the reference noise signal and adjusts the filter to produce the required error signal.

Abstract: A method is disclosed for estimating the impulse response of the earth from Vibroseis data. Based on a time domain system identification approach, the earth's impulse response is estimated by operating on the seismic trace data and the vibrator pilot. Two implementations are discussed. The first is an adaptive method using a sliding data window and the uncorrelated trace data. Preferably, the process used to control the adaptation is the fast Kalman estimation (FKE) technique. This technique, based on recursive least squares, has a fast convergence rate and desirable computational requirements. The second implementation is non-adaptive. It uses the Levinson recursion technique to compute the Wiener filter solution based on the pilot autocorrelation function and the correlated trace data. Simulations demonstrate the capability of the system identification model to resolve reflection events.

Abstract: A method of seismic exploration, wherein one or more vibratory sources are employed to generate an input signal whose frequency varies as a function of time and wherein the signal is reflected and refracted to detector stations from subsurface beds, in which the sources are tested for signal accuracy with respect to a reference. The method includes generating at a first location a system reference signal having a pattern of predetermined phase and frequency characteristics and generating at a first source a vibrator control signal or a motion detector signal. The vibrator control signal or the motion detector signal is converted to constant amplitude so that the signal pattern is represented principally by phase and frequency. The system reference signal is correlated with the vibrator control signal or the motion detector signal to generate a cross-correlation function.

Abstract: In seismic exploration windows from a pair of contiguous traces are used in a process which determines the coherent noise on a basis trace and removes this coherent noise from a prediction trace. The operator of a digital filter is determined by autocorrelating the basis trace, cross-correlating the window of the basis trace, with the window of the prediction trace, and selecting the filter operator which produces the least error between the cross-correlation function and the product of the autocorrelation function and the operator.

Abstract: Apparatus is provided for determining the conformity of an energy pulse generated by a weight drop seismic source to a defined energy pulse characteristic in order that reflections associated with a non-conforming energy pulse can be rejected. The apparatus operates to compare the signature of a weight drop with a signature standard. Incoming seismic data is rejected and not recorded if the difference between the incoming signature pulse shape and the standard signature pulse shape is too great. The pulse shape of the incoming signature is analyzed by comparing a sample of the incoming signature amplitude to upper and lower rejection limits derived from a time correlated amplitude sample of the standard signature. The upper and lower rejection limits against which an incoming signature sample is compared are proportional to the amplitude of the time correlated standard signature sample.

Abstract: In common depth point seismic exploration, seismic traces are corrected for normal moveout and stacked to form a composite trace. The composite trace is successively time shifted to provide a plurality of reference traces characterized by the normal moveout of the seismic traces. The reference traces are crosscorrelated with the seismic traces, and the resulting correlation functions are utilized to enhance the primary reflection signals of the seismic traces.

Abstract: In common depth point (CDP) seismic exploration, a pilot trace is produced from the stacked trace for each CDP set of traces. The pilot trace is crosscorrelated with each trace of the CDP set during selected time windows. The crosscorrelation time shifts are applied to each trace of the CDP set. The time shifted traces of each CDP set are stacked to form a static corrected seismic record section.

Abstract: Methods and apparatus are described for generating and transmitting signals in accordance with a sequence which defines the time relationship of the signals. Each signal has a band width covering several octaves and may be a pulse. During a transmission interval the repetition frequencies of the signals monotonically sweep in a coherent relationship over bands restricted to an octave such that the spectrum of the sequence has substantially constant energy over a frequency range much larger than an octave. The autocorrelation function of the sequence is characterized by an absence of side lobes which would indicate false targets or produce a high noise level upon processing of the signals in an echolocation system, such as a geophysical exploration system in which the seismograms are constructed by cross correlation of the signals which are received from the geological reflection surfaces with a stored replica of the transmitted signals.

Abstract: A method for deriving seismic information through the simultaneous operation of a plurality of vibrational seismic energy source systems such that the information produced by each source system may be separated from the combined recorded information.