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US4608673A
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Minimum phase bandpass filtering of seismic signals
Assignee: ConocoPhillips Co
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Filing: 1983-05-11
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Granted: 1986-08-26
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Expires: 2003-05-11
Abstract
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.
Inventors
- 👤 Gregory D. Lazear
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-10-26 22:32
CPC Classifications
G; G01; G01V; G01V1/00; G01V1/28; G01V1/36; G01V1/364; G01V2210/00; G01V2210/20; G01V2210/27
Claims Analysis
Total Claims: 10
Claim 1
Independent Claim
86 words
A method of filtering crosscorrelated seismic data comprising: constructing a selected bandpass filter operator in the frequency domain having zero phase; transforming said bandpass filter operator and obtaining a minimum phase spectrum, and forming a frequency domain filter operator with the same amplitude spectrum but minimum phase; again transforming said frequency domain filter operator to the time domain to form said minimum phase bandpass filter operator; and convolving said minimum phase bandpass filter operator with said crosscorrelated seismic data to define the data first arrival time.
Claim 2
Independent Claim
86 words
A method of filtering crosscorrelated seismic data comprising: constructing a selected bandpass filter operator in the frequency domain having zero phase; transforming said bandpass filter operator and obtaining a minimum phase spectrum, and forming a frequency domain filter operator with the same amplitude spectrum but minimum phase; again transforming said frequency domain filter operator to the time domain to form said minimum phase bandpass filter operator; and convolving said minimum phase bandpass filter operator with said crosscorrelated seismic data to define the data first arrival time.
Claim 3
Dependent Claim
60 words
A method as set forth in claim 1 wherein said step of transforming comprises: inverse Fourier transforming said bandpass filter operator to the time domain and truncating to obtain a zero phase, symmetric filter operator of selected length; and transforming the logarithm of the amplitude spectrum of the symmetric filter operator to obtain the minimum phase frequency domain filter operator.
Claim 4
Dependent Claim
25 words
A method as set forth in claim 1 wherein said step of again transforming includes: an inverse Fourier transform of said frequency domain filter operator.
Claim 5
Dependent Claim
25 words
A method as set forth in claim 2 wherein said step of again transforming includes: an inverse Fourier transform of said frequency domain filter operator.
Claim 6
Dependent Claim
65 words
A method as set forth in claim 1 wherein said step of transforming comprises: inverse Fourier transforming said bandpass filter operator to the time domain and truncating to produce a zero phase filter operator; and computing one-half times the natural logarithm of the power spectrum of the zero phase filter operator and performing a Hilbert transform to produce said minimum phase frequency domain filter operator.
Claim 7
Dependent Claim
52 words
A method as set forth in claim 5 wherein said step of again transforming comprises: forming the complex exponential of the power spectrum; and inverse Fourier transforming to the time domain and truncating to selected operator length to produce said minimum phase bandpass filter operator for convolution with said crosscorrelated seismic data.
Claim 8
Dependent Claim
104 words
A method as set forth in claim 1 wherein said step of transforming comprises: inverse Fourier transforming said bandpass filter operator to the time domain and truncating to obtain a zero phase, symmetric filter operator of selected length; Fourier transforming said symmetric filter operator to the frequency domain and computing the power spectrum as the magnitude squared at each frequency; computing one-half times the natural logarithm of the power spectrum; inverse Fourier transforming said power spectrum logarithm to the time domain and multiplying by a step function of selected amplitude two and onset at time equals zero; and Fourier transforming said multiplied time function.
Claim 9
Dependent Claim
63 words
A method as set forth in claim 2 wherein said step of again transforming comprises: forming the complex exponential of the logarithm of the power spectrum of the minimum phase frequency domain filter operator; and inverse Fourier transforming to the time domain and truncating to selected operator length to produce said minimum phase bandpass filter operator for convolution with said crosscorrelated seismic data.
Claim 10
Dependent Claim
61 words
A method as set forth in claim 7 wherein said step of again tansforming comprises: forming the complex exponential of the logarithm of the power spectrum of the frequency domain filter operator; and inverse Fourier transforming to the time domain and truncating to selected operator length to produce said minimum phase bandpass filter operator for convolution with said crosscorrelated seismic data.
References Cited (Backward Citations)
USPTO Annuity & Maintenance Windows
| Annuity Stage | Window Opens | Payment Deadline | Surcharge Period Until | Estimated Fee | Status |
|---|---|---|---|---|---|
| 3.5 Years (Year 4) | 1989-08-25 | 1990-02-24 | 1990-08-26 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1993-08-25 | 1994-02-24 | 1994-08-26 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1997-08-25 | 1998-02-24 | 1998-08-26 | $7700.00 | Window Closed / Lapsed |