Method of processing geophysical data to compensate for earth filter attenuation
AssigneeMobil Oil Corporation
InventorsMohamed T. Hadidi, Andrejs Jurkevics, Andrew F. Linville, Jr.
Life of this patent
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Abstract
Method to process seismic data to yield useful information regarding the subsurface area explored. Generated seismic energy travels into a subsurface formation where it is distorted and attenuated. The distorted and attenuated seismic pulse is detected by a geophone or other seismic receiver and recorded. The received seismic traces are first compensated for the attenuation effects of the earth filter and the compensated seismic traces are then used to produce a close approximation of a zero-phase, band-limited output wavelet of the reflectivity of the geophysical formation under exploration.
Claims37
A method of compensating for the effects of intrinsic and apparent attenuation of a seismic signal transmitted through a geophysical formation comprising the steps of:
- determining an antisymmetric component of the cepstrum of an inverse earth filter;
- determining a symmetric component of the cepstrum of said inverse earth filter modified to effect gain limiting;
- combining said modified symmetric component and said antisymmetric compenasted to determine said inverse earth filter of said geophysical formation;
- and
- applying said inverse earth filter to said seismic signal to determine a compensated seismic signal.
A method of compensating for the effects of intrinsic and apparent attenuation of a series of seismic signals transmitted through a geophysical formation comprising the steps of:
- selecting a first seismic signal;
- determining an antisymmetric component of the cepstrum of the inverse earth filter;
- determining a symmetric component of the cepstrum of the inverse earth filter modified to effect gain limiting;
- combining said symmetric and antisymmetric components;
- repeatedly applying said combination to said first seismic signal;
- combining partial results produced by said repeated applications to determine a first compensated seismic signal;
- selecting a next seismic signal;
- and
- repeating said selecting, applying, and combining steps until all seismic signals have been compensated.
A method of compensating the amplitude spectrum of a seismic trace for the effects of earth filtering, nonwhite reflectivity of the subsurface formation being explored and sampling, comprising:
- determining an antisymmetric component of the cepstrum of an inverse earth filter;
- determining a symmetric component of the cepstrum of said inverse earth filter modified to effect gain limiting;
- combining said modified symmetric component and said antisymmetric component to determine said inverse earth filter of said geophysical formation;
- applying said inverse earth filter to said seismic signal to determine a compensated seismic signal;
- whitening effective reflectivity of the amplitude spectrum of said compensated seismic signal;
- reducing the effects of reflectivity leakage on said amplitude spectrum of said compensated seismic signal;
- compensating said amplitude spectrum of said seismic signal to approximate that of an analog seismic wavelet;
- and
- smoothing said compensated amplitude spectrum of said compensated seismic signal to eliminate rapidly varying components of said compensated amplitude spectrum.
A method of processing geophysical data to make it more useful in interpreting the subsurface characteristics of the earth comprising:
- acquiring at least one seismic trace containing information related to the subsurface characteristics of the earth;
- determining an antisymmetric component of the cepstrum of an inverse earth filter;
- determining a symmetric component of the cepstrum of said inverse earth filter;
- combining said modified symmetric component and said antisymmetric component to determine said inverse earth filter of said geophysical formation;
- applying said inverse earth filter to said at least one seismic trace to determine at least one compensated seismic trace;
- determining an amplitude spectrum for said at least one compensated trace;
- whitening effective reflectivity of each of said at least one compensated seismic trace;
- compensating said amplitude spectrum of said at least one seismic trace to approximate an analog seismic wavelet;
- estimating a phase spectrum for said seismic wavelet from said compensated seismic wavelet;
- determining a two sided, least squares filter from said estimated phase spectrum;
- and
- determining an output seismic wavelet from said compensated amplitude spectrum and said estimated phase spectrum by applying said two sided, least squares filter to said compensated amplitude spectrum in the time domain wherein said seismic wavelet is shaped into a zerophase, low sidelobe output wavelet by said two sided, least squares filter.
Dependencies are inferred from the claim text.