EP0602703A2
Expired / Lapsed
EP
⏱️ 0.0 years remaining
Method for improving signal to noise ratio
Assignee: SLB NV
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Filing: 1993-12-01
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Granted: —
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Expires: 2013-12-01
Abstract
Abstract A method for improving the signal to noise ratio from a pair of detectors such as geophones which each detect a noisy signal comprising a signal of interest ( S ) and a noise signal ( N ), wherein the signal of interest ( S ) has a different moveout across the pair of detectors from that of the noise signal ( N ), and the noise signal ( N ) from a given source is detected at the first detector at a time Δ t before the corresponding noise signal is detected at the second detector, the method comprising delaying the noisy signal ( S + N ) detected at the first detector by an amount τ being greater than the moveout of the signal of interest but not more than Δ t and subtracting the delayed signal from that detected at the second detector by means of an adaptive filter so as to minimise the power in the resultant signal The signal detected at the first detection and optionally the resultant signal can also be delayed by an amount τ₂ and the signal detected at the second detector is subtracted from the delayed first detector (and resultant signals) by means of an adaptive fitler so as to minimise the power in the final signal, the delay τ₂ being greater than the moveout of the signal of interest plus the length of the filter but not more than Δ t plus the length of the filter.
Inventors
- 👤 Richard John Meehan
Bibliographic Details
Application Number
—
Jurisdiction
EP
Data Source
google_patents
Last Synchronized
2026-11-05 09:34
CPC Classifications
G; G01; G01V; G01V1/00; G01V1/28; G01V1/36; G01V1/364; G01V2210/00; G01V2210/30; G01V2210/32; G01V2210/34
Claims Analysis
Total Claims: 19
Claim 1
Independent Claim
194 words
A method for improving the signal to noise ratio from a pair of detectors which each detect a noisy signal comprising a signal of interest ( S ) and a noise signal ( N ) the separation of the detectors being such that the noise signal ( N ) detected at a second detector is substantially the same as that detected at a first detector, wherein the signal of interest ( S ) has a different moveout across the pair of detectors from that of the noise signal ( N ), and the noise signal ( N ) from a given source is detected at the first detector at a time Δ t before the corresponding noise signal is detected at the second detector, the method comprising delaying the noisy signal ( S + N ) detected at the first detector by an amount τ being greater than the moveout of the signal of interest but not more than Δ t and subtracting either the delayed signal or the signal detected at the second detector from the other by means of an adaptive filter so as to minimise the power in the resultant signal.
Claim 2
Dependent Claim
25 words
A method as claimed in claim 1, wherein the delayed signal is substracted from that through the second detector by means of the adaptive filter.
Claim 3
Independent Claim
80 words
A method comprising delaying the noisy signal ( S + N ) detected at the first detector by an amount τ₂ and subtracting the signal from the second detector from the delayed signal by means of an adaptive filter so as to minimise the power in the resultant signal, the delay τ₂ being greater than the moveout of the signal of interest plus the length of the filter but not more than Δ t plus the length of the filter.
Claim 4
Dependent Claim
89 words
A method as claimed in claim 2, wherein the signal detected at the first detection and the resultant signal are delayed by an amount τ₂ and the signal from the second detector is subtracted from the delayed first detector and resultant signals by means of an adaptive fitler so as to minimise the power in the final signal, the delay τ₂ being greater than the moveout of the signal of interest plus the length of the filter but not more than Δ t plus the length of the filter.
Claim 5
Independent Claim
23 words
A method as claimed in any of claims 1 - 4, wherein the pair of detectors form part of a larger detector array.
Claim 6
Dependent Claim
15 words
A method as claimed in claim 5, wherein the array includes a beam steering arrangement.
Claim 7
Independent Claim
17 words
A method as claimed in any preceding claim, wherein the signal of interest is a seismic signal.
Claim 8
Dependent Claim
23 words
A method as claimed in claim 7, wherein the seismic signal is generated by a drill bit during the drilling of a well.
Claim 9
Dependent Claim
16 words
A method as claimed in claim 7 or 8, wherein the noise N comprises ground roll.
Claim 10
Dependent Claim
179 words
A detector system for improved signal to noise ratio performance comprising: a) a pair of detectors arranged such that a signal of interest ( S ) has a different moveout across the pair of detectors from a noise signal ( N ) which arrives at a first detector of the pair at a time Δ t before the corresponding noise signal arrives at the second detector of the pair; the separation of the detectors being such that the noise signal ( N ) detected at the second detector is substantially the same as that detected at the first detector. b) means for delaying the noisy signal ( S + N ) detected by the first detector by an amount τ being greater than the moveout of the signal of interest but not more than Δ t ; c) means for subtracting either of the delayed signal or the signal ( S + N ) detected by the second detector from the other, said means comprising an adaptive filter arranged to minimise the power in the resultant signal after subtraction.
Claim 11
Dependent Claim
23 words
A detection system as claimed in claim 10 wherein the adaptive filter subtracts the delayed signal from the signal from the second detector.
Claim 12
Dependent Claim
122 words
A detector system as claimed in claim 10, wherein moveout across the pair of detectors from a noise signal ( N ) which arrives at a first detector of the pair at a time Δ t before the corresponding noise signal arrives at the second detector of the pair; the delaying means delays the noisy signal ( S + N ) detected by the first detector by an amount τ₂; and the adaptive filter subtracts the signal ( S + N ) detected by the second detector from the delayed signal, the amount τ₂ being greater than the moveout of the signal of interest plus the length of the filter but not more than Δ t plus the length of the filter.
Claim 13
Dependent Claim
91 words
A system as claimed in claim 10, further comprising means delaying the signal detected at the first detector and the resultant signal by an amount τ₂; and means for subtracting the signal detected at the second detector from the delayed first detector and resultant signals, said means comprising an adaptive filter arranged to minimise the power in the final signal; the delay τ₂ being greater than the moveout of the signal of interest plus the length of the filter but not more than Δ t plus the length of the filter
Claim 14
Independent Claim
23 words
A system as claimed in any of claims 10 - 13, wherein the pair of detectors form part of a larger detector array.
Claim 15
Dependent Claim
15 words
A system as claimed in claim 14, wherein the array includes a beam steering arrangement.
Claim 16
Dependent Claim
22 words
A system as claimed in any of claim 10 - 15, further comprising a seismic source for generating the signal of interest.
Claim 17
Dependent Claim
23 words
A system as claimed in claim 16, wherein the source comprises a drill bit which generates the signals during drilling of a well.
Claim 18
Dependent Claim
26 words
A system as claimed in claim 17, wherein the noise N is generated by a rig on the surface from which the well is being drilled.
Claim 19
Independent Claim
25 words
A system as claimed in any of claims 16 - 18, wherein the detectors comprise a linear arrangement with the source of the noise signal.
References Cited (Backward Citations)
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