US4520467A
Expired / Lapsed
US
⏱️ 0.0 years remaining
Marine seismic system
Assignee: Shell USA Inc
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Filing: 1982-03-18
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Granted: 1985-05-28
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Expires: 2002-03-18
Abstract
Abstract A method for eliminating ghosts, or reflections from the air/water interface of a body of water, from seismic signals detected at a predetermined depth is provided. The method employs both a pressure sensor and a motion sensor. A seismic signal and its corresponding ghost signal detected by a pressure sensor is filtered as a function of depth of the sensor to provide a preselected amplitude and zero phase shifted band-limited spike signal at an arrival time corresponding to the arrival time midway between the seismic and ghost arrival times. Similarly, a seismic and ghost signal from a motion sensor is filtered as a function of depth of the sensor to provide a band-limited spike having an arrival time midway between the seismic and ghost arrival times. The filtered motion and pressure spikes are added together in proportion to their respective signal-to-noise ratios. The proportionally added signal is a ghost free seismic signal having a maximum signal-to-noise ratio for each frequency component and may be employed in further seismic processing steps.
Inventors
- 👤 Albert J. Berni
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-10-28 18:49
CPC Classifications
G; G01; G01V; G01V1/00; G01V1/38; G01V1/3808; G01V1/28; G01V1/36; G01V1/364; G01V2210/00; G01V2210/50; G01V2210/56
Claims Analysis
Total Claims: 9
Claim 1
Independent Claim
158 words
A method for obtaining a ghost-free marine seismic signal, comprising: supplying acoustic energy to a body of water above substrata to be seismically explored; detecting reflected seismic signals indicative of said substrata and corresponding ghost signals from the air-water interface with pressure sensors and with motion sensors; filtering each of said detected seismic and corresponding ghost signals to produce band-limited spike waveforms having arrival times intermediate the arrival times of said seismic and ghost signals as a function of the depth of detection of said signals; determining the signal-to-noise ratio for said pressure sensors and for said motion sensors; filtering said spike waveforms with zero phase filters having a band-limited frequency dependent amplitude spectrum functionally related to the signal-to-noise ratios for said sensors; and adding said filtered spike waveforms from said pressure sensors to said filtered spike waveforms from said motion sensors to form a filtered spike waveform having a maximum signal-to-noise ratio for each frequency component therein.
Claim 2
Independent Claim
158 words
A method for obtaining a ghost-free marine seismic signal, comprising: supplying acoustic energy to a body of water above substrata to be seismically explored; detecting reflected seismic signals indicative of said substrata and corresponding ghost signals from the air-water interface with pressure sensors and with motion sensors; filtering each of said detected seismic and corresponding ghost signals to produce band-limited spike waveforms having arrival times intermediate the arrival times of said seismic and ghost signals as a function of the depth of detection of said signals; determining the signal-to-noise ratio for said pressure sensors and for said motion sensors; filtering said spike waveforms with zero phase filters having a band-limited frequency dependent amplitude spectrum functionally related to the signal-to-noise ratios for said sensors; and adding said filtered spike waveforms from said pressure sensors to said filtered spike waveforms from said motion sensors to form a filtered spike waveform having a maximum signal-to-noise ratio for each frequency component therein.
Claim 3
Dependent Claim
50 words
A method as recited in claim 1, wherein said zero phase filters further comprise: a frequency dependent first weighting function for said pressure signals; and a frequency dependent second weighting function for said motion signals, wherein the sum of said first and second weighting functions by frequency component is one.
Claim 4
Dependent Claim
38 words
A method as recited in claim 2, wherein said first weighting function comprises the signal-to-noise ratio of the pressure sensor divided by the sum of the signal to noise ratios of said pressure sensor and said motion sensor.
Claim 5
Dependent Claim
36 words
A method as recited in claim 3, wherein said second weighting function comprises the signal-to-noise ratio for said motion sensor divided by the sum of the signal-to-noise ratios of said pressure sensor and said motion sensor.
Claim 6
Dependent Claim
14 words
A method as recited in claim 1, wherein said motion sensors comprise acceleration sensors.
Claim 7
Dependent Claim
50 words
A method as recited in claim 5, wherein said zero phase filters further comprise: a frequency dependent first weighting function for said pressure signals; and a frequency dependent second weighting function for said acceleration signals, wherein the sum of said first and second weighting functions by frequency component is one.
Claim 8
Dependent Claim
36 words
A method as recited in claim 6, wherein said first weighting function comprises the signal-to-noise ratio of the pressure sensor divided by the sum of the signal-to-noise ratios of said pressure sensor and said acceleration sensor.
Claim 9
Dependent Claim
36 words
A method as recited in claim 7, wherein said second weighting function comprises the signal-to-noise ratio for said acceleration sensor divided by the sum of the signal-to-noise ratios of said pressure sensor and said acceleration sensor.
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USPTO Annuity & Maintenance Windows
| Annuity Stage | Window Opens | Payment Deadline | Surcharge Period Until | Estimated Fee | Status |
|---|---|---|---|---|---|
| 3.5 Years (Year 4) | 1988-05-27 | 1988-11-26 | 1989-05-28 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1992-05-27 | 1992-11-26 | 1993-05-28 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1996-05-27 | 1996-11-26 | 1997-05-28 | $7700.00 | Window Closed / Lapsed |