US5010526A
Expired / Lapsed
US
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Method of digital filtering
Assignee: Mobil Oil AS
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Filing: 1990-07-30
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Granted: 1991-04-23
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Expires: 2010-07-30
Abstract
Abstract An improved method for filtering noise bands from seismic data is described. The data is analyzed to determine the frequency component of the undesired noise, and a precise autocorrelation function is generated and used to design a filter to remove the undesired frequency component from the data. The filter can be band pass, band reject, notch, low pass, or high pass, and multiple bands of noise can be removed from the seismic data in a single filtering operation.
Inventors
- 👤 Andrew F. Linville, Jr.
- 👤 Thomas E. Shirley
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-11-09 09:21
CPC Classifications
G; G01; G01V; G01V1/00; G01V1/28; G01V1/36; G01V1/364; G01V1/366; G01V2210/00; G01V2210/30; G01V2210/32; G01V2210/324
Claims Analysis
Total Claims: 12
Claim 1
Independent Claim
155 words
A method of filtering data records, comprising the steps of: determining the frequency of energy to be filtered from the records; choosing the bandwidth of the filter to be applied; selecting a filter order n; computing the exact autocorrelation function R x (τ) for one or more bands of energy to be filtered according to the following equation: ##EQU2## wherein R x (τ) is the exact autocorrelation function of the noise; B is the bandwidth of the noise to be removed; f 0 is the center frequency of the band of noise to be removed; and τ is 0, 1, . . . n-1; using the autocorrelation function thus determined to generate a series of filter coefficients h 0 , h 1 , . . . h n-1 ; and applying said filter coefficients h 0 , h 1 , . . . h n-1 to the data to filter out the undesired frequency components.
Claim 2
Independent Claim
155 words
A method of filtering data records, comprising the steps of: determining the frequency of energy to be filtered from the records; choosing the bandwidth of the filter to be applied; selecting a filter order n; computing the exact autocorrelation function R x (τ) for one or more bands of energy to be filtered according to the following equation: ##EQU2## wherein R x (τ) is the exact autocorrelation function of the noise; B is the bandwidth of the noise to be removed; f 0 is the center frequency of the band of noise to be removed; and τ is 0, 1, . . . n-1; using the autocorrelation function thus determined to generate a series of filter coefficients h 0 , h 1 , . . . h n-1 ; and applying said filter coefficients h 0 , h 1 , . . . h n-1 to the data to filter out the undesired frequency components.
Claim 3
Dependent Claim
28 words
The method of claim 1 wherein said filter coefficients are calculated by inserting the values of the autocorrelation function R x (τ) into a predictive Wiener-Levinson autocorrelation matrix.
Claim 4
Dependent Claim
35 words
The method of claim 2, wherein white noise is added to the diagonal of the matrix prior to calculation of the filter coefficients h 0 , h 1 , . . . h n-1 .
Claim 5
Dependent Claim
30 words
The method of claim 1, comprising the further step of autocorrelating the filter coefficients h 0 , h 1 , . . . h n-1 to generate a zero-phase filter.
Claim 6
Dependent Claim
32 words
The method of claim 1 wherein said step of determining the frequency of energy to be removed is performed by taking the Fourier transform of the input signal and determining undesired frequencies.
Claim 7
Independent Claim
222 words
A method of removing noise components from seismic data recorded in seismic exploration wherein seismic energy sources are activated at spaced locations along a line of exploration, and signals responsive to reflection of the seismic energy within the earth are recorded as a function of time at spaced locations along the line of exploration to produce a series of seismic traces, said seismic traces comprising seismic data components and noise components, said method comprising the steps of: determining the frequency of energy to be filtered from the records; choosing the bandwidth of the filter to be applied; selecting a filter order n; computing the exact autocorrelation function for one or more bands of energy to be filtered according to the following equation: ##EQU3## wherein: R x (τ) is the exact autocorrelation function of the noise; B is the bandwidth of the noise to be removed; f 0 is the center frequency of the band of noise to be removed; and τ is 0, 1, . . . n-1; using the autocorrelation function R x (τ) thus determined to generate a series of filter coefficients h 0 , h 1 , . . . h n-1 ; and applying said filter coefficients h 0 , h 1 , . . . h n-1 to the data to filter out the undesired frequency components.
Claim 8
Independent Claim
222 words
A method of removing noise components from seismic data recorded in seismic exploration wherein seismic energy sources are activated at spaced locations along a line of exploration, and signals responsive to reflection of the seismic energy within the earth are recorded as a function of time at spaced locations along the line of exploration to produce a series of seismic traces, said seismic traces comprising seismic data components and noise components, said method comprising the steps of: determining the frequency of energy to be filtered from the records; choosing the bandwidth of the filter to be applied; selecting a filter order n; computing the exact autocorrelation function for one or more bands of energy to be filtered according to the following equation: ##EQU3## wherein: R x (τ) is the exact autocorrelation function of the noise; B is the bandwidth of the noise to be removed; f 0 is the center frequency of the band of noise to be removed; and τ is 0, 1, . . . n-1; using the autocorrelation function R x (τ) thus determined to generate a series of filter coefficients h 0 , h 1 , . . . h n-1 ; and applying said filter coefficients h 0 , h 1 , . . . h n-1 to the data to filter out the undesired frequency components.
Claim 9
Dependent Claim
27 words
The method of claim 6 wherein said coefficients are calculated by inserting the values of the autocorrelation function R x (τ) into a predictive Wiener-Levinson autocorrelation matrix.
Claim 10
Dependent Claim
32 words
The method of claim 7, wherein white noise is added to the matrix diagonal prior to calculation of the coefficients h 0 , h 1 , . . . h n-1 .
Claim 11
Dependent Claim
31 words
The method of claim 6, comprising the further step of autocorrelating the filter coefficients h 0 , h 1 , . . . h n-1 to generate a zero phase filter.
Claim 12
Dependent Claim
34 words
The method of claim 6 wherein said step of determining the frequency of the energy to be removed is performed by taking the Fourier transform of the input signal and determining the undesired frequencies.
References Cited (Backward Citations)
US4104611A
Cited
US4853903A
Cited
USPTO Annuity & Maintenance Windows
| Annuity Stage | Window Opens | Payment Deadline | Surcharge Period Until | Estimated Fee | Status |
|---|---|---|---|---|---|
| 3.5 Years (Year 4) | 1994-04-22 | 1994-10-22 | 1995-04-23 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1998-04-22 | 1998-10-22 | 1999-04-23 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 2002-04-22 | 2002-10-22 | 2003-04-23 | $7700.00 | Window Closed / Lapsed |