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: A field quality control system and real-time method for evaluating the performance of swept frequency vibrators is provided. The system includes independent sensing means adapted to be mounted with the swept frequency vibrators for developing signals representative of reaction mass accelerations and baseplate accelerations, and means for monitoring the swept frequency vibrator's pilot signal. The system also includes a signal calculating means for determining vibrator operating characteristics from the pilot sweep signal, reaction mass acceleration signal, and baseplate acceleration signal and processing means for processing the vibrator operating characteristics to obtain analysis characteristics for evaluating and adjusting the performance of the swept frequency vibrator. In operation, the present invention provides a method for analysis characteristics to analyze and adjust the performance of swept frequency vibrators in real-time on location.

Abstract: A method of producing random sweeps for seismic vibrator sources is described which produces correlograms with reduced side lobe contamination. Digital random phase digital codes activate non-impulsive sources. Detected signals are processed using periodic sweep correlations. The method is especially useful in urban areas where permitting requirements limit the drive level and frequency range of a vibratory seismic source.

Abstract: The present invention relates generally to a method of geophysical exploration and more particularly to a novel method for imaging multicomponent seismic data to obtain better depth images of the earth's subsurface geological structure as well as better estimates of compressional and shear wave interval velocities. In particular, measures are obtained of imparted seismic wavefields incident on reflecting interfaces in the earth's subsurface and of resulting seismic wavefields scattered therefrom. The incident and scattered seismic wavefields are employed to produce time-dependent reflectivity functions representative of the reflecting interfaces. By migrating the time-dependent reflectivity functions, better depth images of the reflecting interfaces can be obtained. For a dyadic set of multicomponent seismic data, the dyadic set of multicomponent seismic data are partitioned so as to separate the variously coupled incident and reflected wavefields in the recorded multicomponent seismic data.

Abstract: A transmission which requires only a single source to transmit is generated in accordance with a code which is binary (a pulse train having two levels which produces a specific harmonic line spectrum). The pulses are generated by pulse time modulation of the position and duration of pulses in a sweep which extends to the upper end of the spectrum.

Abstract: Method of instantaneous acoustic logging within a wellbore.The method is characterized in that it consists of locating on drill-pipe and ground recordings elementary recordings corresponding to one and the same depth level of the drilling tool, in grouping these elementary recordings in pairs, then in intercorrelating said recordings of the pairs so as to produce in respect of each pair a correlated signal which is representative of the acoustic energy produced and of the difference in travel times of the waves received on sensors from which the pair of recordings has been obtained.A particular application is for the determination of a seismic wellbore profile.

Abstract: A method of filtering and combining seismic data, such as data from two or more seismic sources having different spectral characteristics. A plurality of seismic signals are transmitted into a subterranean earth formation and a resulting data trace for each seismic signal is recorded. A correlating signal is generated for each data trace, such that the sum of the correlations of each correlating signal with its associated trace is an approximately minimum phase signal whose frequency amplitude spectrum is the sum of the frequency amplitude spectra of the seismic signals. In a preferred embodiment, the correlating signals are generated by obtaining reference signals representing the seismic signals prior to propagation through the earth formation, concatenating these reference signals and inserting a zero-amplitude signal between each reference signal, and then performing least-squares deconvolution on the concatenated signal.

Abstract: A method of seismic prospecting in which there is employed conventional upsweep and downsweep and opposed polarity of signals that are being sent into the earth as seismic signals and in which there is introduced a taper at the common frequency at the common time on the respective upsweep and downsweep signals to reduce the most significant part of the correlation noise, yet provide the advantages of each of the methods of using opposite phase polarity, to cancel and using opposite upsweep and downsweep to achieve reduction in the noise experienced, as well as the reduction of the most significant part of the correlation noise that distorts the desired zero-phase Klauder wavelet.

Abstract: The present invention generally relates to a method of seismic exploration. In particular, a novel method of obtaining a vertical seismic profile of the earth's subterranean formation surrounding a well borehole with a horizontally direct swept frequency vibrator and a multicomponent sonde is provided. Additionally, a method is provided to azimuthally align the geophones of the multicomponent sonde having horizontal axes.

Abstract: A filtering system is provided for acquiring and processing signals using a sampled filter for signal separation and signal enhancement; such as for determining locations, distances, and times in a geophysical exploration system. Signature signals permit mixing and seperation with sampled filters, such as for sharing common circuitry and for increasing the amount of acquired information. A sampled filter, such as a digital correlator, is provided for generating high resolution output data in response to low resolution input data processed with low resolution computational circuits. A real-time time-domain correlator is provided with single-bit resolution computational elements to provide improved correlation filtering. A high speed real-time correlator is provided to enhance signals with compositing-after-correlation and with correlation using a plurality of correlation operators.

Abstract: A first sweep signal consists of a plurality of waveforms having non-invariant fundamental periods exhibiting a monotonic frequency progression of at least one octave over the duration of the sweep. Each waveform may consist of an ordered set of asymmetrical pulses distributed within the period of the waveform in a prescribed sequence as a function of time. A second sweep signal is orthogonalized with respect to the first by time-reversing the distribution-sequence of the pulse set.

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.

Abstract: Distortion in vibrator-type seismic records is corrected by measuring and using the actual ground force imparted by the source to develop an inverse filter. The ground force signal and the reflected seismic data are both subjected to the same deconvolution or other standard processing technique, thereby automatically filtering out flaws introduced by any such technique.

Abstract: Data points for a sinusoidal waveform are assigned 2 bit values which indicate the state of the amplitude (positive or negative) and the slope of the sinusoidal signal at the particular data point (positive or negative). The 2 bit values for a plurality of sinusoidal waveforms are compared to determine the phase misalignment between the plurality of sinusoidal waveforms.

Abstract: Seismic exploration method and apparatus in which interference signals received by the sensing geophones from the seismic vibration source are cancelled by employing a signal representative of the seismic vibration source and combining it with the output from the sensing geophones.

Abstract: The invention provides an apparatus for seismic prospecting which is to effect a correlation in real time between a pilot signal and a picked-up seismic signal. With N being the number of samples corresponding to the desired thoroughness of investigation, the apparatus comprises the following: a buffer of N samples of the pilot signal; at least one buffer for a sample of the picked-up signal; at least one calculation circuit, in which the correlation operations are carried out; at least one result memory, which is to contain the N points of the correlation function; and a circuit for addressing the memories.

Abstract: For the correction of the time-of-flight of an ultrasonic signal, the measurement signal (s) produced by an ultrasonic transducer (3) is digitized, stored and compared with a reference signal (s*). The comparison is performed by way of different relative shifts between the measurement signal and the reference signal. The value of the shift where both signals correspond best is used for the correction.

Abstract: A method of monitoring underground processes in which changes of material properties of underground strata occur in a limited area, especially in regard to in-situ combustions, gasifications in coal and petroleum deposits, in order to localize and determine the degree of change of material properties of underground strata, includes emitting exactly reproducible time-sequential seismic signals in each geological strata where changes are expected to take place. The signals are recorded in the appropriate geological stratum at one or more positions, or in the same position. The signals are stacked with signals of reverse sign. The magnitude of the difference signals obtained and their propagation time are determined.

Abstract: A seismic wave generator and method of using it, which comprises a vertical array of sources at known spacings, for detonation in a seismic wave propagating medium of known seismic velocity; means to initiate the sources in time sequence in a selected series of known different time intervals and recording the seismic waves at a distant location to provide a first electrical signal; and correlating the first electrical signal with a second electrical signal derived from the pattern of initiation, as modified by the travel times of the waves between the several separate charges.

Abstract: A method is disclosed for editing seismic traces gathered by large multichannel collection systems using a pattern analysis of the noise spectrum of each trace. Analysis is limited to only a small time window, say the last second of the trace. In that way a minimum number of quantitative variables and mathematical manipulations are required to carry out the invention. On-site as well as off-site, processing of the traces in accordance with the method of the present invention, is contemplated.

Abstract: An acoustic energy mode propagation speed or travel time measurement system for use in well logging is disclosed. A downhole sonde is provided with an acoustic transmitter and at least one acoustic receiver. The transmitter is repetitively driven with a unique or characteristic swept frequency signal. Propagated acoustic energy detected at the receiver is cross-correlated with the characteristic transmitter swept frequency signal to provide indications of the arrival of various modes of acoustic energy propagation at the receiver. Logs as a function of borehole depth of the speed of propagation of the various modes of propagation may be derived.

Abstract: In one exemplar embodiment, an improved method is provided for compensating received propagated seismic signals for the absorption by the earth of all frequencies of a vibrator source signal. The received seismic data is crosscorrelated with the original source signal and a Fourier amplitude spectral analysis obtained. Then an attenuation function is determined by the attenuation exhibited by the spectrum. The quantified attenuation function is then applied as a compensation function to the original source signal to obtain a "weighted" vibrator sweep signal that is then used in crosscorrelating with the received seismic data to compensate for the frequency dependent attenuation in the earth of received propagated seismic data.

Abstract: A method is provided for obtaining wide band seismograms made from a plurality of narrow band seismic surveys using vibrator type sources. Several different narrow frequency band seismograms are obtained using vibrator type signal sources. The narrow band seismogram having different frequency band responses are stacked, or added together, to provide a single wide band seismogram having improved signal to noise characteristics.

Abstract: A method of seismic exploration comprises transmitting waves from transmission sources into the medium to be explored and picking up signals in a receiver and recording these as traces, the signals being produced by reflection in the medium, the sequential transmission of the sources taking place at intervals less than the reflection time of the longest transmitted waves, the repeated transmission of any one source taking place at intervals at least equal to the said reflection time and therein being an intercorrelation function of a series of transmission instants of all the sources and a series of transmission instants of any one of the sources to give a relationship between the maximum peak amplitude and the secondary residue amplitude greater than a predetermined value and grouping the recorded traces corresponding to the same reflection point, adjusting the traces in relation to the associated source providing the information relating to the reflection point and adding together the adjusted traces relati

Abstract: A method of seismic exploration and a system which provides the capability for increasing the number of depth points from which seismic data are acquired are disclosed. This increase in data is realized without increasing the number of recording channels or the number of geophone stations employed in the system. A higher common depth point multiplicity is achieved by separating energy sources in relation to geophone stations. The recording system is capable of automatically sorting out the data from different energy sources and storing it in different blocks of a memory. Since substantially all available recording time is fully utilized by using energy sources to their optimum efficiency, higher common-depth-point multiplicity can be achieved with minimum field costs.

Abstract: A rotating eccentric weight apparatus and method for generating coded shear wave signals for use in seismic exploration. The apparatus includes a rotatable eccentric and a position sensor capable of detecting each instant that the eccentric passes a particular angular position about its axis of rotation and generating a code signal for use in correlating the raw seismic data obtained. In one embodiment, the apparatus includes an outrigger shovel which transmits a sinusoidal shear wave signal generated by the rotating eccentric while the rest of the apparatus is caused to alternately decouple from and impact against the earth surface to transmit a coded train of pressure wave impulses into the earth.

Abstract: This invention provides for transmission of composite swept sine wave seismic signals wherein auto-correlation side lobes of such signals are reduced. The frequency spectrum of a desired swept sine wave seismic signal is divided into a number of consecutive segments, and the segments are arranged to form a sequence of segments by the order of frequency content. Component swept sine wave seismic signals each covering a segment in the sequence are generated simultaneously from the same location to produce the desired seismic signal. The component swept sine wave seismic signals are generated in a manner so that they alternate as upsweeps and downsweeps for consecutive segments in the sequence of segments. The seismic signal comprising the sum of the component swept sine wave seismic signals will have an auto-correlation function with reduced side lobes.

Abstract: Seismic exploration on land and on ocean beds is performed by emitting vibrational acoustic signals of long time-duration within a desired frequency spectrum at one or a number of points, the signals corresponding to the waves received from the reflectors being then processed. The method further consists in forming the complex spectrum of the received signal corresponding to the emitted signal in respect of each frequency band, in forming the complex spectrum of a reference of the emitted signal in respect of each frequency band and in dividing the complex spectrum of the received signal by the complex spectrum of the reference of the emitted signal, at least an external portion of each complex spectrum being eliminated in the case of each complex spectrum.

Abstract: A seismic exploration method in which a rotating eccentric weight seismic source is employed to transmit a coded energy signal into the earth. A position sensor mounted on the source directly detects the instants at which the rotating eccentric passes a particular angular position about its axis of rotation, and generates a code signal which is used to correlate the raw seismic data. Preferably the source is allowed to decouple from the earth surface such that the coded energy signal transmitted into the earth is a coded impulse train.

Abstract: A seismic exploration method in which a coded energy signal is generated and transmitted into the earth, the seismic energy reflected from within the earth is sensed and sampled to form a raw trace, the raw trace is crosscorrelated with a record of the coded energy signal, and a predictive operator derived from the autocorrelation function of the coded energy signal is subtractively applied to the crosscorrelated trace to remove correlation residuals, and thereby produce a high quality processed trace. Geophysical principles are used to interpret the processed trace and identify subterranean mineral deposits of interest. Based on this interpretation at least one well is drilled to further explore and/or develop the mineral deposits of interest.

Abstract: This invention relates to pulse radar detection of targets in extended media, including natural phenomena such as oil, coal and ore deposits within the earth. In particular, this invention relates to a pulse radar system employing a synthetic pulse formed from a Fourier spectrum of frequencies generated and detected by a digitally controlled transmitter and receiver circuits.

Abstract: Methods and apparatus describedmaximize, within a predetermined frequency band, the continuous or near-continuous transmission of broadband acoustic power into a medium having a finite tensile strength such as water or earth. Such methods and apparatus also minimize, for a given broadband acoustic power level in a given frequency band, the negative dynamic pressure or stress excursion of an acoustic signal with respect to the average pressure or stress present in the absence of the signal. Such signals may be transmitted for geophysical exploration purposes. The signals place the medium alternately under compressive and tensile stresses with respect to some average stress, where the time duration of the application of the compressive stress is short compared with the time duration of the application of the tensile stress. The tensile stress does not exceed the tensile strength of the medium or its interfaces.

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: Quasi periodic pulse trains are generated and swept in repetition frequency over an octave. Spectral harmonics of the pulse trains which prevent the trains from having a constant or "flat" power spectrum over a frequency range much greater than an octave are reduced or eliminated by adjusting the shape of the pulses in the trains. By means of selecting the timing of the pulses, other harmonics are reduced or preferentially augmented. The spectral energy of the signals which are generated during a transmission interval is of the type which possesses an autocorrelation function with a narrow main lobe and low side lobe levels which is especially suitable for echo location purposes such as in geophysical exploration in which seismograms are constructed by cross correlation of the signals which are transmitted with those which are received from the geological reflection surfaces.

Abstract: This invention relates to an improved system for employing seismic techniques for surveying the subsurface structures of the earth. The invention relates particularly to an improved system for generating, collecting and processing the data during the course of exploration with a group of trucks that travel over the surface of the earth and intermittently stop to perform the required operations. The processing aids in the performance of the generating and collecting step and in the further processing of the collected data. And the data resulting from processing in this invention are transferred to a computer center for further processing. In this system, use is made of two programmable computers to facilitate concurrent processing of seismic waves received in successive setups in different ways.

Abstract: This invention relates to an improved system for employing seismic techniques for surveying the subsurface structures of the earth. The invention relates particularly to an improved system for generating, collecting and processing the data during the course of exploration with a group of trucks that travel over the surface of the earth and intermittently stop to perform the required operations. The processing aides in the performance of the generating and collecting step and in the further processing of the collected data. And the data resulting from processing in this invention are transferred to a computer center for further processing. In this system, use is made of two programmable computers to facilitate concurrent processing of seismic waves received in successive setups in different ways.

Abstract: This invention concerns a synchronizing control for an electro-hydraulic seismic vibrator, which control utilizes a magnetic tape cassette reader that puts out a train of pulses of changing time spacing of a preselected pattern. This operates a counter which controls the address of a read-only memory which has a selected number of memory locations, each one holding a corresponding one of a sequence of digitized values forming a single cycle of a sine wave. By continuing to operate the counter, each of the values stored in the memory is sequentially placed in an output circuit to provide a digitized sinusoidal reference sweep signal. The cassette reader signal also drives a second counter through a frequency ratio control of the pulses provided by the cassette. By this means, the second counter can be varied to count at a different rate from the first counter.

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.