Kinematical filters

Seismic wave filed is a superposition of waves and noises, and noises can be both coherent and non-coherent. Algorithm of 2D filtering is one of the most efficient approaches for both coherent and non-coherent noises. There are three basic methods of filtering implemented in Prime: in time-spatial domain (x - t), in spatial-frequency domain (x - w) and in 2D Fourier domain (k - w). Local tau-pi transformation is used for kinematical filtering in t-x domain.

Kinematical filters based on the signal pass

Suppose, that travel time curves of useful seismic waves were approximately obtained after preliminary analysis. Filter must pass these waves and also those waves which rely to the specified fan without any distortions. All other waves are considered to be noises and they must be removed.

Adaptive kinematical filters

In cases of noisy data or travel time curves non-hyperbolicity it could be difficult to estimate the signal and noise kinematics. Adaptive filtering is very useful in this case. It allows analyzing wave field for every point and finding the signal and noise.

Adaptive filter-mask

More or less exact model of noise waves (for example multiples) may be known when we attenuate coherent noises. In this situation adaptive filter-mask can be applied. It can kinematically analyze the model of noise and make decision about presence or absence of noise for every data sample. The main advantage of using this method than using those methods, which directly subtract model of noise from initial field is no necessity of full correspondence of modeled dynamical features to the real dynamical features.

Filtering in offset-domain, stacked and migrated sections

Described filtering approaches can be applied not only to the CDP gathers, but also to the offset-sections, time sections or results of migration in t-x domain.

Polarization filtering – is a separation of two or three-component CSP gathers with extraction of P-waves and S-waves. A priori velocity in upper part must be known. Kinematical filters can be used for noise extraction before elimination.

Example of initial CDP gather, used for fan-filter testing in pass modification.
Example of initial CDP gather, used for fan-filter testing in pass modification.
Result of fan-filtering without anti-alias algorithm application.
Result of fan-filtering without anti-alias algorithm application.
Result of fan-filtering with anti-alias algorithm application.
Result of fan-filtering with anti-alias algorithm application.
Example of horizon-consistent spectra examples. Horizon was chosen in the area of interference. Upper spectrum obtained from initial data, spectrum after fan-filtering without anti-alias algorithm application is shown in the middle, lower spectrum compute
Example of horizon-consistent spectra examples. Horizon was chosen in the area of interference. Upper spectrum obtained from initial data, spectrum after fan-filtering without anti-alias algorithm application is shown in the middle, lower spectrum compute
Amplitude spectra obtained for the specified area, shown before. Spectrum after fan-filtering without anti-alias algorithm application (on the left), spectrum after fan-filtering with anti-alias algorithm application (on the right).
Amplitude spectra obtained for the specified area, shown before. Spectrum after fan-filtering without anti-alias algorithm application (on the left), spectrum after fan-filtering with anti-alias algorithm application (on the right).
Example of initial CDP gather, used for fan-filter testing in pass modification.
Example of initial CDP gather, used for fan-filter testing in pass modification.
Result of noise elimination without anti-alias algorithm application.
Result of noise elimination without anti-alias algorithm application.
Result of pas fan-filtering after noise elimination without anti-alias algorithm application.
Result of pas fan-filtering after noise elimination without anti-alias algorithm application.
Result of noise model subtraction from initial wave field with anti-alias algorithm application.
Result of noise model subtraction from initial wave field with anti-alias algorithm application.
Result of pas fan-filtering after noise elimination with anti-alias algorithm application.
Result of pas fan-filtering after noise elimination with anti-alias algorithm application.
Initial marine gather.
Initial marine gather.
Result obtained with anti-alias algorithm application.
Result obtained with anti-alias algorithm application.
Initial CDP gather.
Initial CDP gather.
Result of interpolation in offset-domain.
Result of interpolation in offset-domain.
Result of noise rejection.
Result of noise rejection.
Wave field with amplitudes, recovered after noise rejection.
Wave field with amplitudes, recovered after noise rejection.
Model of multiples.
Model of multiples.
Result of filter-mask application.
Result of filter-mask application.