69 results about "Seismic vibrator" patented technology

This invention relates in general to vibroseis and, more specifically, but not by way of limitation, to the enhancement and / or signal strength optimization of low frequency content of seismic signals for use in surveying boreholes and / or subsurface earth formations. In embodiments of the present invention, physical properties of a seismic vibrator may be analyzed and used to provide for determination of a driving force necessary to drive a reaction mass to produce a sweep signal with enhanced low frequency content for injection into the ground for vibroseis. In certain aspects, the physical properties may be considered independent of any geophysical properties related to operation of the seismic vibrator.

A method for the simultaneous operation of multiple seismic vibrators using unique modified pseudorandom sweeps and recovery of the transmission path response from each vibrator is disclosed. The vibrator sweeps are derived from pseudorandom binary sequences modified to be weakly correlated over a time window of interest, spectrally shaped and amplitude level compressed. Cross-correlation with each pilot signal is used to perform an initial separation of the composite received signal data set. Recordings of the motion of each vibrator are also cross-correlated with each pilot, windowed, and transformed to form a source cross-spectral density matrix in the frequency domain useful for source signature removal and for additional crosstalk-suppression between the separated records. After source signature removal in the frequency domain an inverse transform is applied to produce an estimate of each source-to-receiver earth response in the time domain. The method has application to both land and marine geophysical exploration.

A method for generating seismic energy for subsurface surveying includes operating a first seismic vibrator and operating at least a second seismic vibrator in a body of water substantially contemporaneously with the operating the first seismic vibrator. Each vibrator has a different selected frequency response, and the vibrators each are operated at a depth in the water such that a surface ghost amplifies a downward output of each vibrator within a selected frequency range. A signal used to drive each vibrator has a frequency range corresponding to the frequency range of each vibrator.

This invention relates in general to vibroseis and, more specifically, but not by way of limitation, to the enhancement and / or signal strength optimization of low frequency content of seismic signals for use in surveying boreholes and / or subsurface earth formations. In embodiments of the present invention, physical properties of a seismic vibrator may be analyzed and used to provide for determination of a driving force necessary to drive a reaction mass to produce a sweep signal with enhanced low frequency content for injection into the ground for vibroseis. In certain aspects, the physical properties may be considered independent of any geophysical properties related to operation of the seismic vibrator.

The present invention is a method of processing seismic data in which one or more seismic vibrators are activated with one or more pilot signals and vibrator motions are recorded along with seismic data. Vibrator signatures are computed from measured vibrator motions, such as the ground force signal. A desired impulse response is specified from either a measured vibrator motion or from test data or field data from a location near the location from which the seismic data was acquired. A deconvolution filter is computed from the impulse response and the vibrator signature. Alternatively, a single separation and deconvolution filter is derived from the impulse response and from vibrator signatures from multiple vibrators and sweeps. The deconvolution or deconvolution and separation filter is used to process the seismic data. The vibrators are then moved to a new location, and the activation is repeated.

The present invention is a method of processing seismic data in which one or more seismic vibrators are activated with one or more pilot signals and vibrator motions are recorded along with seismic data. Vibrator signatures are computed from measured vibrator motions, such as the ground force signal. A desired impulse response is specified from either a measured vibrator motion or from test data or field data from a location near the location from which the seismic data was acquired. A deconvolution filter is computed from the impulse response and the vibrator signature. Alternatively, a single separation and deconvolution filter is derived from the impulse response and from vibrator signatures from multiple vibrators and sweeps. The deconvolution or deconvolution and separation filter is used to process the seismic data. The vibrators are then moved to a new location, and the activation is repeated.

A method for controlling output of a marine seismic vibrator includes operating the vibrator using a predetermined driver signal. A vibrator output signal is measured at at least two different places on the vibrator. The at least two measured vibrator output signals are used to determine a corrected driver signal, wherein the corrected driver signal results in fewer harmonics of fundamental frequencies in the vibrator output. The vibrator is operated using the corrected driver signal.

A method for generating seismic energy for subsurface surveying include operating a first seismic vibrator above an area of the subsurface to be surveyed and operating at least a second seismic vibrator above the area substantially contemporaneously with the operating the first seismic vibrator. The first and the second vibrators each have a different selected frequency response. The first and second vibrators each is operated by a same direct sequence spread spectrum signal, wherein a different number of modulation operations for each logical value in the direct sequence spread spectrum signal is selected for each vibrator.

A seismic vibrator includes a transducer, a reactive mass, a base plate to couple motion of the reactive mass to subsurface formations and a linkage system configured to couple motion of the transducer to the reactive mass and the base plate. The linkage system cooperates with the reactive mass and the transducer to define a first resonant frequency and a second resonant frequency within a range of 1 to 300 Hz.

A method for generating seismic energy for subsurface surveying includes operating a first seismic vibrator and operating at least a second seismic vibrator substantially contemporaneously with the operating the first seismic vibrator. A driver signal to each of the first and the at least a second seismic vibrators that are substantially uncorrelated with each other.

A method for simultaneously operating multiple seismic vibrators using continuous sweeps (little or no “listening” time between sweeps) for each vibrator, and recovering the separated seismic responses for each vibrator with the earth signature removed. Each vibrator is given a unique, continuous pilot signal. The earth response to the motion of each vibrator is measured or estimated. The vibrator motion records for each vibrator and the combined seismic data record for all the vibrators are parsed into separate shorter records. The shorter records are then used to form a system of simultaneous linear equations in the Fourier transform domain, following the HFVS method of Sallas and Allen. The equations are then solved for the separated earth responses.

A method for operating marine seismic vibrators includes towing at least a first and a second marine seismic vibrator in a body of water beneath the hull of a vessel. At least a third marine seismic vibrator is towed at a selected depth in the water other than beneath the hull of the vessel. The at least first, second and third vibrators are operated to sweep through respective frequency ranges. The first and second frequency ranges have lowermost frequencies and uppermost frequencies respectively differing by a selected sub-harmonic frequency range. The third frequency range has a lowermost frequency at least equal to the uppermost frequency of one of the first and second frequency ranges and traverses a seismic frequency range of interest.

A seismic source signal generator includes a mass, a primary accumulator and a secondary accumulator, the secondary accumulator having an internal volume smaller than an internal volume of the primary accumulator. A method for generating a signal using a seismic vibrator includes operating the seismic vibrator using hydraulic fluid, damping hydraulic pressure deviations in the hydraulic fluid using a first accumulator in hydraulic communication with the hydraulic fluid, and damping pressure deviations in the hydraulic fluid using a second accumulator in hydraulic communication with the hydraulic fluid, the second accumulator having an internal volume smaller than an internal volume of the first accumulator.

A method for generating seismic energy for subsurface surveying include operating a first seismic vibrator above an area of the subsurface to be surveyed and operating at least a second seismic vibrator above the area substantially contemporaneously with the operating the first seismic vibrator. The first and the second vibrators each have a different selected frequency response. The first and second vibrators each is operated by a same direct sequence spread spectrum signal, wherein a different number of modulation operations for each logical value in the direct sequence spread spectrum signal is selected for each vibrator.

A method and system of operating single vibrator source points for seismic data acquisition includes acquiring real-time field survey locations for a first plurality of seismic vibrators, determining at least one geometrical relationship between each of the first plurality of seismic vibrators as a function of the field survey locations, selecting a second plurality of seismic vibrators from the first plurality of vibrators as a function of the at least one geometrical relationship, selecting source parameter data for the second plurality of seismic vibrators as a function of the field survey locations and driving the second plurality of seismic vibrators to propagate seismic energy into the earth. A third plurality of vibrators is selected based on geometrical relationships and associated source parameters are determined based on vibrator locations. Multiple vibrator groups may acquire data continuously without interruption.

A method and system of operating single vibrator source points for seismic data acquisition includes acquiring real-time field survey locations for a first plurality of seismic vibrators, determining at least one geometrical relationship between each of the first plurality of seismic vibrators as a function of the field survey locations, selecting a second plurality of seismic vibrators from the first plurality of vibrators as a function of the at least one geometrical relationship, selecting source parameter data for the second plurality of seismic vibrators as a function of the field survey locations and driving the second plurality of seismic vibrators to propagate seismic energy into the earth. A third plurality of vibrators is selected based on geometrical relationships and associated source parameters are determined based on vibrator locations. Multiple vibrator groups may acquire data continuously without interruption.

The invention relates to a vibroseis device for marine geophysical exploration, in particular to a marine electromagnetic type shallow seismic vibrator system. The system is formed by a main controller and a vibration generator array. The main controller consists of a CPU, a seismograph synchronizer trigging unit, a parameter module, an electric level switching module, a signal generating module and a power amplifying module. The vibration generator array is fixed onto a steel shelf by a fixing substrate. A fixing bracket, magnetic steel, a magnetic polar plate and an iron core are rigidly connected with a housing. Moving coils are fixed on a middle axle of the vibration generator. The middle axle of a vibration generator is connected with a moving substrate. The moving coils are connected with a load bearing spring by aluminum alloy. The load bearing spring is fixed onto the housing through rivets. A supporting spring which is connected with the moving substrate by bolts is fixed onto the steel shelf through the bolts. The system is comparatively high in scanning frequency section of signal up to 1 to 1500Hz, good in repeatability of the signal, and optimal in the energy output of the vibration generator. The system meets the requirements of high resolution earthquake exploration at marine shallow layers and solves the influence of marine earthquake exploration carriers on seismic focus.