Abstract: A method for interval velocity analysis and reflector position determination from before stack seismic data includes developing a constant travel-time curve for a source and receiver pair. The process is repeated with other source and receiver pairs in order to generate a set of constant travel-time curves, and a series of the travel-time curves define an envelope curve for the reflector which is sharply focused at the true interval velocity. An additional embodiment provides a method for quantifying the velocities and permitting selection of the best velocity. Use of this selection method greatly enhances the speed and the overall operation accuracy.

Abstract: A method is disclosed for developing a weight function for a trace stack from the weight functions derived from the respective weight functions of an ensemble of individual separate input traces. Also disclosed is the method of developing the resulting weighted trace stack. Finally, disclosed also is a method of noise suppression utilizing weight function manipulation from a plurality of related seismic traces.

Abstract: VSP-based method for tieing surface data shot with different types of seismic sources together. VSP data is acquired using the same types of seismic sources utilized to acquire the surface data. The acquired VSP data is used to produce a correction operator for application to the surface data.

Abstract: A method for identifying anomalous noise amplitudes in seismic records by deriving a measured amplitude factor over predetermined periods of time or time windows for a predetermined number of traces comprising the records is disclosed. A noise-free amplitude factor for the same periods of time and number of traces is also computed using a Gauss-Siedel method of matrix inversion. A ratio of the measured and noise-free amplitude factors is made to determine a correction factor which is compared to a user defined threshold value for determining a presence of anomalous noise amplitudes in the seismic records. Based on the comparison of the correction factor to the threshold value, the user determines whether to suppress or correct traces experiencing the anomalous noise amplitudes.

Abstract: The invention comprises a method of geophysical exploration wherein a signal is generated at the lower end of a drill string and propagates into the earth and up said drill string. The signal is detected at the top of said drill string and at other locations substantially at the earth's surface. The signal detected at the top of the drill string is utilized to develop an operator to reduce the magnitude of drill string multiples in the signal detected by the field sensors.

Abstract: Method and apparatus for cancelling nonstationary sinusoidal noise from seismic data. An estimate of the sinusoidal noise component is applied to a contaminated signal containing both a sinusoidal noise component and a non-sinusoidal data component to cancel the sinusoidal noise component of the signal. The estimate of the sinusoidal noise component is determined using continuous adjustments of the phase, frequency and amplitudes of the quadrature outputs of a local signal. The estimate of the sinusoidal noise component is subtracted from the contaminated signal and the resultant signal, which is an estimate of the data component of the contaminated signal, is utilized in adjusting the phase, frequency and amplitudes of the local reference sine-cosine signal.

Abstract: An improvement in a method of treating seismic data in which predictive noise, as measured along one of the axes is discriminated and subtracted from the total signal along another of the axes recorded by geophone recording the reflection from subterranean strata of energy input from a source at the surface.

Abstract: A method for continuous velocity estimation of seismic data uses non-linear signal matching. Common depth point trace data is examined at selected offsets and non-linear signal matching is performed to derive moveout information from which the RMS and interval velocities may be further estimated. Non-linear signal matching for selected offsets of each CDP trace gather functions to derive characteristic match curve data at selected depths or travel time intervals. The match curve data inherently contains moveout information that relates to energy velocities for the particular trace position. Derived velocity data for selected time depths may then be output across a line of survey.

Abstract: The present invention is directed to a method of inverting seismic traces Sk by determining the series R={r.sub.i } representative of the seismic reflection coefficients from geological strata. The method includes the steps of determining an approximate solution to R.degree. by minimizing an entropy type function H(R)=.SIGMA.f(r.sub.i) under constraints related to the upgoing wavefield Uk and the downgoing wavefield Dk; determining a correction value .DELTA.R by minimizing a linear function J(.DELTA.R) under linear constraints related to the noise in the traces and to the time-depth curve extracted from the traces; and calculating R=R.degree.+.DELTA.R, representative of the reflection coefficients. In a variant, the selection of the approximate solution R.degree. is guided by taking into account information contained in one or more logs, and determining .DELTA.R so that the series R satisfies the stacking velocities which result from surface seismic processing.

Abstract: The present invention provides methods for processing converted wave seismic data which includes, fractional point gathering of the data in a manner consistent with a selected velocity model, dynamic correction of the data using parameters measured from the data to account for the asymmetric travel path of the converted wave rays and stacking the dynamically corrected data. Methods are also provided for updating the velocity model.

Abstract: A common bandwidth determination method for two disparate seismic datasets includes developing a weighted average of first least-squares filters assuming the data from the first dataset is the input and the data from the second dataset is the desired output, developing a weighted average of second least-squares filters assuming the data from the second dataset is the input and the data from the first dataset is the desired output, determining a first transfer function from the first weighted average filter design and a second transfer function from the second weighted average filter design, plotting respective amplitude and phase spectra using each of the first and second transfer functions, plotting the product of the amplitude spectra and the sum of the phase spectra and determining the common bandwidth where the amplitude spectra is one and the phase spectra is zero.

Abstract: Method of restoring null traces in seismic records. A trace for which restoration of the data is desired, as well as adjoining traces on each side of the null trace are selected. A series of cross-correlations are determined for all points on the selected trace. Restoration of the data points is conducted by transforming the series of points of the adjacent traces corresponding to the maximum cross-correlation for the point into a Fourier representation, zero-padding the Fourier representation and producing a restored data point from the zero-padded data representation. The procedure is repeated for each point along the trace being restored. This procedure interpolates a trace between two original traces without altering the original data.

Abstract: The present invention relates to a method for identifying and separating the effects of elastic and anelastic formation properties in a seismic signal representative of the earth's response to seismic energy imparted therein. The seismic signal is decomposed into a measure of the absorptive contrast and impedance contrast across reflecting boundaries in the earth's subterranean formations. The resulting measures of impedance contrast can be used to obtain a measure of the earth's elastic properties. The resulting measures of the absorptive contrast can be used to obtain measures of the earth's anelastic properties.

Abstract: An electronic system automatically detects significant events in a seismic trace. The seismic trace is defined as a series of consecutive points, equally spaced in time. The system provides for taking the Nth derivative of the trace at each of the points. The system has the capability of identifying the time of the zero-crossings of the Nth derivative and of establishing the amplitude of the trace at the time of the zero-crossing of the Nth derivative. Memory is provided for storing the amplitude of the trace and the times of the zero crossings in the Nth derivative. Finally, displays are provided for displaying the traces and the zero-crossings in the Nth derivative as a hard copy of visual display.

Abstract: A method for predicting the ground vibration and airborne noise at any position resulting from a blasting operation using the data obtained from one or more single-charge low level blasts. By using convolution in the frequency domain, large charge weight nonlinear vibrations are considered, such that the optimum excitation frequency (detonation delays) is induced for minimizing objectionable ground and air vibrations and noise. The method also allows optimization of the number, position and loading of the blast holes, and the number and position of charges detonated per delay period, to produce maximum removal of material without damage to surrounding structures.

Abstract: The invention is a method of performing a plurality of vibratory seismic surveys simultaneously. A plurality of vibratory sources transmit signals into the earth. Each vibratory source successively transmits the same signal, except that an offset phase of the signal is selectively shifted for successive transmissions. The offset phase of the signal transmitted by each vibratory source is selected to enable the signal from each of the vibratory sources to be recovered by data processing.

Abstract: To help a user program a computer target system to solve problems, the computer system is provided with predefined capabilities and the user is provided with a knowledge system that includes knowledge about applying the capabilities to effectively and efficiently solve the user's problems. The knowledge system provides automatic programming for solving problems within a particular domain, rejects problems that cannot be solved using the available capabilities of the target computer, and explains how and why a certain program was generated or why a program cannot be generated to solve a given problem.

Abstract: A method for determining the position of a subterranean plane reflector relative to a known location on the earth surface from unprocessed seismic data received at a number of colinear acoustic receiver locations. A traveltime curve associated with the reflector is identified from the seismic data. From two points on the traveltime curve, a signal indicative of the reflector's dip angle is generated. Using the dip angle signal, signals indicative of the position of each imaged point of the reflector are generated. The inventive method assumes knowledge of the average velocity of seismic waves in the subterranean formation above the reflector, and that such formation region can adequately be considered to have constant velocity equal to such average velocity. The method may be applied to process raw data generated during a vertical seismic profiling operation.

Abstract: A computer system reviews and modifies horizons tentatively defined by a network of pairs of turnings. The curvature for each of the paths of turnings of the network in both the X and Y directions is assessed. If the curvature exceeds a predetermined value in any of the paths, that path is terminated at the point of excessive curvature. Also, each pair of turnings is tested to determine whether it is in a closed loop made up of four turnings which in turn make up four pairs of turnings to determine that there is three-dimensional continuity. The horizons are thereby modified if modification is required.

Abstract: A method of seismic exploration of the subsurface of the earth. Seismic reflection data are gathered in a selected area. The seismic data are combined with available non-seismic data to define an initial two-dimensional lithologic model. Based upon the initial model, a set of synthetic seismic data is generated. The degree of correspondence between the set of synthetic reflection data and the gathered seismic data is determined. The initial model-parameters are systematically perturbed during a series of iterations until a desired degree of correspondence has been achieved, resulting in a final lithologic model.

Abstract: A computer system extracts horizons, each defined by a network of points in a first format from within a three-dimensional volume. Each point is tagged with a plurality of parameters including links in the X and Y direction for interconnecting the points. The system accesses any one of the points in the network then accesses every point that is linked directly or indirectly to the first accessed point. An address pointer is established for each of the accessed points, to define a second format. A second format is in a two-dimensional array and any point that is accessed a second time is rejected to prevent any spiraling of the horizon. The second format may be stored and displayed.

Abstract: A method for attenuating multiples in common depth point data whereby common depth point data is received and spike deconvolution maybe performed on the data. The data is constant velocity stacked and gap deconvolution is performed. The primary stack velocity is determined and all data having a velocity other than the primary stack velocity is muted. All scans within the constant velocity stack are composited. These composites are arranged in proper order and displayed.

Abstract: A method for quantitatively distinguishing seismic events on a seismic record for inferring changes in the geological character of the subterranean formations. Reflection coefficients are obtained for such seismic events and a first set of attributes indicative of amplitude variations in the offset seismic signals corresponding to the seismic event as a function of incident angle are obtained therefrom. The first set of attributes provide a seismologist with a diagnostic tool for quantitatively evaluating subtle changes in the seismic event. A second set of attributes which are functions of the first set of attributes provide the seismologist with additional diagnostic tools for evaluating subtle changes in the seismic events.

Abstract: An improved apparatus and method for calculating automatic gain correction to be applied to seismic samples is disclosed which features apparatus and method for calculation of the average absolute value of a window of samples in the vicinity of the sample being processed, the calculation being performed a first time with the window shifted toward a first side of the sample and a second time with the window shifted toward a second side of the sample, and selecting for use in gain correction the minimum of the two calculated average absolute values, such that high amplitude samples in the vicinity of relatively low amplitude events is precluded from causing unrealistic shadowing around such events.

Abstract: A computer system automatically determines pairs of significant turnings related to the same seismic event in adjacent seismic traces of a three-dimensional seismic volume, wherein a turning is defined as a zero-crossing in the Nth derivative of the seismic trace. The times of the turnings of a first trace are compared with the times of the turnings of a second trace, and vice versa. The mutual smallest differences between times of turnings is detected and those turnings having the smallest mutual differences are paired, thereby designating the turnings that are mutual nearest neighbors, provided that the signs of the (N+1)th derivatives are the same (positive or negative). The system has the capability to compare the signs. The system repeats the comparison and pairing throughout the three-dimensional seismic volume.

Abstract: An electronic system automatically produces representations of three-dimensional recommended horizons from processed seismic data. Significant events, in the form of turnings, are identified in all of the digitized traces that make up the processed seismic data. Pairs of significant events in adjacent traces are determined. The system determines these pairs through a mutual nearest neighbor technique, together with a technique for detecting similar signs. The system measures the curvature of the path formed by the paired turnings in successive digital traces and terminates the path at any point where the curvature exceeds a predetermined limit. The system then looks for three-dimensional continuity by looking for a closed loop of at least four turnings making up four pairs of turnings. These techniques yield at least one horizon represented in a first format.

Abstract: By using wave tracking rather than a downward continuation concept, two sets of elastic wave fields (one generated by a seismic source, the other recorded by multicomponent geophones) are migrated separately and are then imaged. The process is repeated for common shot gathers, and then the images (associated with each common midpoint gather), are stacked.As a consequence of wave tracking, migration operations are preferably performed in the time domain using finite difference discretization equations involving vector properties of the fields but without having to reduce the latter to one-way wave equations.

Abstract: This invention relates to a method of increasing resolution of high-intensity amplitude events in seismic records provided by common midpoint collection methods (CMP) wherein nonsymmetrical travel paths of incident and reflected rays of the generated conventional waves are taken into account prior to trace stacking irrespective of dip or depth of the target reflector. In accordance with the invention, the converted phases of the conventional seismic wave, are processed as to define a series of common reflection point (CRP) coordinates each associated with a gather of converted traces as if a source associated with a given corrected trace was placed at each CRP and activated followed immediately by the relocation of a detector at the CRP and the reception of converted phases of the generated wave comprising the trace.

Abstract: A process for better defining first break seismic energy travel times for correlated seismic return signals that consists of constructing a minimum phase bandpass filter having bandwidth narrower than the vibrational seismic return signals and convolving the filter with the return signals to convert the seismic return signals to a causal wave form.

Abstract: The disclosed invention is a method of seismic exploration using non-impulsive vibratory sources activated by stationary, Gaussian codes in urban areas. The method adds a distortion-free quality to the full-waveform seismic records.

Abstract: This invention relates to a method of increasing resolution of high-intensity amplitude events in seismic records provided by common midpoint collection methods (CMP) wherein nonsymmetrical travel paths of incident and reflected rays of the generated conventional waves are taken into account prior to trace stacking due to the dip and depth of the target reflector.

Abstract: This invention relates to a method of increasing resolution of high-intensity amplitude events in seismic records provided by common midpoint collection methods (CMP) wherein nonsymmetrical travel paths of incident and reflected rays of the generated conventional waves (due to dip and depth) are taken into account prior to trace stacking.

Abstract: Disclosed is a method for estimating and correcting source and receiver statics contained in recorded and gathered seismic traces. Measurements based on the time of arrival of reflection and refraction signal components in the recorded and gathered traces are used to produce source-receiver statics estimates, which are in turn used to correctly time shift the individual traces of the gather for subsequent common depth point (CDP) gathering and stacking.

Abstract: In marine seismic exploration, seismic energy is transmitted through a water layer into the earth and seismic reflection signals from subsurface interfaces are recorded. Any undulating water bottom distortion in the recorded reflection signals is removed by replacing the seismic energy velocity in the water layer with a velocity matching that of the earth medium below the water bottom.

Abstract: This invention consists of producing a two-dimensional display from exploration seismic data designed to indicate zones of anomalous low velocity in the subsurface. Such zones may be indicative of porosity and the possible occurrence of hydrocarbons. They will be localized in terms of position along the seismic profile and in approximate zone of reflection arrival time. Data used in making the display are derived from both the CDP stacked seismic profile and corresponding velocity analyses used also to stack the data itself. Stacking velocity curves are plotted according to CDP location for each reflector designated by an interpreter to be of interest. These curves are overlain in pairs using calibration calculations and empirical criteria. Calibration helps smooth "noisy" values and compensates for velocity variations resulting from changes in separation or dip of the two reflectors from which the overlain velocity curves derive.

Abstract: Methods and apparatus are described for estimating parameters, such as slowness and attenuation, of composite acoustic waves obtained in the course of sonic logging of formations traversed by a borehole. Sonic energy is sensed arriving at a plurality of points spaced vertically along the borehole after refraction, reflection and direct transmission through and along the formations. A window is established of predetermined length and moveout and the composite waves are multiplied by the window. A Fourier transform is obtained of the windowed data and the data are simultaneously analyzed to obtain an estimate of the parameters. The procedure is repeated for different window moveouts and index positions along the composite waves. The analysis is performed at each window position and moveout to obtain the best estimate of the parameters.

Abstract: Sweeps of seismic signals consisting of pulse trains having a predetermined number of pulses in which the periods or durations of the pulses are randomized and in which the wave shape and relative time displacements of the pulses in different trains provides substantially constant spectral level over a frequency range containing several octaves even though the durations of the pulses correspond to a frequency range not exceeding an octave during the sweep are transmitted through the medium being explored such as an earth formation to receptors such as geophones or hydrophones. Groups of signals contained in less than the entire length of the sweep which are transmitted and which are received can be cross correlated to vary the effective duration of the sweep. The cross correlation output of successively occurring sweeps may be stacked to reduce the side lobe amplitude of the cross correlation outputs from each sweep, from which outputs seismograms may be constructed.

Abstract: In seismic exploration, an improved synthetic acoustic log is produced from seismograms by combining band limited reflectivity and velocity functions, both of which are obtained from the seismograms. The reflectivity function is obtained by deconvolving the field seismograms, transforming the reflectivity function so obtained into the frequency domain, and filtering the frequency domain representation to suppress frequencies below the seismic band. The velocity functions is obtained by applying a velocity spectra technique to the field seismograms to produce an acoustic log, transforming the acoustic log into the frequency domain, filtering to suppress all frequencies in the seismic pass band and converting back into the time domain.

Abstract: A method for improvement of the signal-to-noise ratio of seismic data records comprising determination of the angle of incidence of acoustic waves transmitted into the earth with respect to subterranean reflecting layers which yields minimum attenuation of the acoustic wave during passage through intermediate layers is disclosed. The offset or distance between source and receiver is then selected so that the waves used to generate representations of the structure of the earth are incident on the reflector at substantially the optimal angle, thus yielding maximum signal strength, and maximizing the signal-to-noise ratio. Minimum offsets, to eliminate multiple surface/evaporite layer reflections from seismic records may be indicated as well.

Abstract: A method for deriving seismic information of more generalized nature over a relatively large and previously unexplored expanse of land to determine relevant strike, dip, velocity and related information. The method consists of the placing of a plurality of seismic sources and receivers in respective lines arranged in a cross pattern, each line being generally at right angles each to the other, and thereafter exciting the sources and recording the received energy for further processing to derive the strike, dip and velocity information for selected strata by using travel times of signal return.

Abstract: A multiple coverage seismic exploration technique provides for a plurality of seismic trace recordings along a line of exploration. From these recordings, sets of common-offset-distance traces are gathered. Initial estimates are made of the apparent dips associated with the seismic reflection signals across each set of common-offset-distance traces. These initial dip estimates are smoothed and the sets of common-offset-distance traces filtered along the apparent dips associated with the smoothed dip estimates to enhance the signal-to-noise ratio of the primary reflection signals.

Abstract: A novel universal signal generator is disclosed comprising a composite system including a library or bank of signals consisting of pre-recorded signals of desired form which may be selected as the output of the apparatus. The output of the library or bank of signals may be varied in a manner which is permutated, systematic, random, jittered or wobulated, or in accordance with a predetermined mathematical curve. The output of the bank or library of signals, either as is or as modified, may be fed through a suitable correlator and/or a power spectra density comparator. The signal output, as is or as modified, or the output from the correlator or the power spectra density comparator may be modified by a suitable secondary modulator or second signal generator. A recording mechanism is provided for amplifying and recording a signal from within the system on separator recording tracks in both a forward and reverse direction.

Abstract: A multi-purpose seismic transducer includes a first seismic sensor having a first transfer function. A transfer-function shaping filter is coupled to the output of the first seismic sensor. The filter is adjustable to shape the first transfer function to match a plurality of different second transfer functions.

Abstract: The specification discloses a method and system wherein an operator interacts with an automatic data processing and display system to classify and sort subsurface reflective surfaces or segments in a multidimensional context. The technique utilizes a properly programmed general purpose digital computer in combination with a plurality of storage tube display screens. Seismic reflection data in the form of computer picked reflection segments, hereinafter referred to as seismic segment data, produced from previous computer processing steps is entered into the computer. Displays of the velocity, amplitude, dip and length of the segments in a space gate are then provided on the display screens. A data responsive surface having a network of conductive wires and a detecting stylus are utilized by the operator to operate upon the displayed segment data to classify primary segments and to define boundaries relative to each of the parameter displays.

Abstract: A seismic data processing method in which seismic traces (each trace containing a signal resulting from reflection of a seismic signal at a location within the earth, and each trace being associated with at least one point in a two-dimensional spatial grid (x,y)) are subjected to Fourier transformations, the coefficients of the Fourier-Transformed traces are subjected to a recursive KF migration operation, and the migrated traces are thereafter inverse-Fourier-transformed. When displayed, the processed seismic data accurately represents the position within the earth of whatever caused the reflection. The method may be employed to process stacked seismic traces, each associated with a single point (x,y) in the grid, or may be employed to process unstacked seismic traces, each associated with both a seismic source location (x.sub.s,y.sub.5) and a different seismic receiver location (x.sub.r,y.sub.r) in the grid.