EP0273722A2
Expired / Lapsed
EP
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Signal processing to enable utilization of a rig reference sensor with a drill bit seismic source
Assignee: Gas Technology Institute
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Filing: 1987-12-23
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Granted: —
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Expires: 2007-12-23
Abstract
Abstract An apparatus (10) for providing while drilling information on a subterranean geologic formation (28) includes a drilling rig (12) and a rotary drill bit (18) attached to the drilling rig (12) for providing seismic waves as it drills in the earth (16). Geophones (20) are spaced from the rotary drill bit (18) in the earth (16) and receive in direct seismic wave paths (26) and seismic wave paths (30) reflected from the subterranean geologic formation (28) the seismic waves provided by the drill bit (18). A reference sensor (24) is located on the drilling rig (12). The seismic signals sensed by the reference sensor (24) and by the geophones (20) are cross-correlated to separate the drill bit generated signals from interference signals by combining the reference signals and the signals received by the geophones (20). The cross-correlated reference signals and the signals received by the geophones (20) are separated into a first group of the drill bit generated seismic signals travelling to the geophones (20) in direct paths and a second group of the drill bit generated seismic signals travelling to the geophones (20) in paths reflected from the subterranean geologic formation (28). The cross-correlation provides a domain where drill bit generated energy can be distinguished from interference. The two groups of the drill bit generated seismic signals can then be used to image the subsurface seismically so as to improve the chances of discovering hydrocarbons. The technique is applicable to land operations and to drilling from an offshore platform over water.
Inventors
- 👤 James Rector
- 👤 Bruce Marion
- 👤 Bernard Widrow
- 👤 Iraj A. Salehi
Bibliographic Details
Application Number
—
Jurisdiction
EP
Data Source
google_patents
Last Synchronized
2026-10-28 01:29
CPC Classifications
G; G01; G01V; G01V1/00; G01V1/40; G01V1/42; G01V1/28; G01V1/36; G01V1/364; G01V1/366; G01V2210/00; G01V2210/10; G01V2210/16; G01V2210/161
Claims Analysis
Total Claims: 34
Claim 1
Independent Claim
133 words
An apparatus for providing while drilling information on a subterranean geologic formation, which comprises a drilling rig, a rotary drill bit attached to said drilling rig for providing seismic waves as it drills in the earth, at least one seismic wave sensor spaced from said rotary drill bit in the earth for receiving via direct seismic wave paths and seismic wave paths reflected from the subterranean geologic formation the seismic waves provided by said drill bit, a reference sensor located on or proximate to said drilling rig, and a means connected to receive the reference signal from said reference sensor and the drill bit generated signals from said at least one seismic wave sensor to distinguish the drill bit generated signals from interference signals by cross-correlating the reference and seismic wave sensor signals.
Claim 2
Independent Claim
133 words
An apparatus for providing while drilling information on a subterranean geologic formation, which comprises a drilling rig, a rotary drill bit attached to said drilling rig for providing seismic waves as it drills in the earth, at least one seismic wave sensor spaced from said rotary drill bit in the earth for receiving via direct seismic wave paths and seismic wave paths reflected from the subterranean geologic formation the seismic waves provided by said drill bit, a reference sensor located on or proximate to said drilling rig, and a means connected to receive the reference signal from said reference sensor and the drill bit generated signals from said at least one seismic wave sensor to distinguish the drill bit generated signals from interference signals by cross-correlating the reference and seismic wave sensor signals.
Claim 3
Dependent Claim
49 words
The apparatus for providing information on the subterranean geologic formation of Claim 1 additionally comprising a means connected to receive the reference signals for reference deconvolution and a means connected to receive the cross-correlated reference and seismic wave sensor signals for eliminating rig generated energy from the reference signals.
Claim 4
Dependent Claim
103 words
The apparatus for providing information on the subterranean geologic formation of Claim 2 additionally comprising a means connected to receive the cross-correlated reference and seismic sensor signals for separating the seismic wave sensor signals into a first group of the seismic wave sensor signals representing the drill bit generated seismic waves received by the said least one seismic wave sensor in the direct seismic wave paths, and a second group of the seismic wave sensor signals representing the drill bit generated seismic waves received by the at least one seismic wave sensor in the seismic wave paths reflected by the subterranean geologic formation.
Claim 5
Dependent Claim
90 words
The apparatus for providing information on the subterranean geologic formation of Claim 3 additionally comprising a means connected to the first group of the seismic wave sensor signals to derive a deconvolution operator, a means connected to the second group of seismic wave sensor signals and to said deconvolution operator deriving means to deconvolve the second group of the seismic wave sensor signals and means connected to the deconvolved second group of the seismic wave sensor signals to form a common reflection point image while said drill bit is drilling.
Claim 6
Dependent Claim
35 words
The apparatus for providing information on the subterranean geologic formation of Claim 1 in which said at least one seismic wave sensor comprises a plurality of sensors located proximate to a surface of the earth.
Claim 7
Dependent Claim
27 words
The apparatus for providing information on the subterranean geologic formation of Claim 1 additionally comprising means connected to receive the reference signals for deconvolving the reference signals.
Claim 8
Dependent Claim
36 words
The apparatus for providing information on the subterranean geologic formation of Claim 6 in which said reference signal deconvolving means is configured to provide an approximation to an inverse of the reference signals reversed in time.
Claim 9
Dependent Claim
60 words
The apparatus for providing information on the subterranean geologic formation of Claim 1 additionally comprising means connected to the cross correlated reference signals and seismic wave sensor signals for attenuating interference signals generated by said drilling rig from the seismic wave sensor signals based on moveout differences between the interference signals and the drill bit generated seismic wave sensor signals.
Claim 10
Dependent Claim
61 words
The apparatus for providing information on the subterranean geologic formation of Claim 8 in which said interference signal attenuating means is configured to attenuate the interference signals by time shifting the interference signals so that they have zero moveout, averaging a series of the cross-correlations together and subtracting the averaged cross-correlation from the cross-correlated reference signals and seismic wave sensor signals.
Claim 11
Dependent Claim
73 words
The apparatus for providing information on the subterranean geologic formation of Claim 1 in which said at least one seismic wave sensor comprises an array of seismic wave sensors, said apparatus additionally comprising means connected to the seismic wave sensors for attenuating interference signals generated by said drilling rig from the seismic wave sensor signals by combining signals of the sensor array to attenuate lower apparent velocity signals radiated by said drilling rig.
Claim 12
Dependent Claim
84 words
The apparatus for providing information on the subterranean geologic formation of Claim 10 in which said interference signal attenuating means comprises a spatial filter configured to transform cross-correlated signals from a given group of said seismic wave sensor array and from a series of drilling depths to a domain of frequency-wavenumber with a two-dimensional Fourier transform and then separate the interference signals from the seismic wave sensor signals on the basis of apparent velocity in the form of a slope in the frequency-wavenumber domain.
Claim 13
Dependent Claim
69 words
The apparatus for providing information on the subterranean geologic formation of Claim 1 additionally comprising means connected to the cross-correlated signals from the reference signals and seismic wave sensor signals for attenuating interference signals generated by said drilling rig from the seismic wave sensor signals by combining a subset of the cross-correlated signals from a selected drilling depth to attenuate lower apparent velocity signals radiated by the drilling rig.
Claim 14
Dependent Claim
39 words
The apparatus for providing information on the subterranean geologic formation of Claim 1 additionally comprising means for converting the reference signals to signals corresponding to the seismic waves generated by said drill bit by time shifting the reference signals.
Claim 15
Dependent Claim
40 words
The apparatus for providing information on the subterranean geologic formation of Claim 13 in which said reference signal converting means is connected to time shift the reference signals after cross-correlation of the reference signals and the seismic wave sensor signals.
Claim 16
Dependent Claim
54 words
The apparatus for providing information on the subterranean geologic formation of Claim 14 additionally comprising means connected to the cross-correlated and time-shifted signals for determining interval velocities based on travel-time difference from two different drill bit depths divided into differential path length from said drill bit to said at least one seismic wave sensor.
Claim 17
Dependent Claim
41 words
The apparatus for providing information on the subterranean geologic formation of Claim 14 additionally comprising means connected to the cross-correlated and time-shifted signals for providing a common reflection point image of the subterranean geologic formation below a shallowest drill bit depth.
Claim 18
Dependent Claim
60 words
The apparatus for providing information on the subterranean geologic formation of Claim 1 in which said means for separating the cross-correlated reference and seismic wave sensor signals into the first and second groups is configured to separate the seismic wave sensor signals into the first and second groups on the basis of moveout differences between the first and second groups.
Claim 19
Dependent Claim
98 words
The apparatus for providing information on the subterranean geologic formation of Claim 17 in which said at least one seismic wave sensor comprises an array of seismic sensors and said interference signal attenuating means comprises a spatial filter configured to transform cross-correlated signals from a given group of said seismic wave sensor array and from a series of drilling depths to a domain of frequency-wavenumber with a two-dimensional Fourier transform and then separate the interference signals from the seismic wave sensor signals on the basis of apparent velocity in the form of a slope in the frequency-wavenumber domain.
Claim 20
Dependent Claim
61 words
The apparatus for providing information on the subterranean geologic formation of Claim 17 in which said interference signal attenuating means is configured to attenuate the interference signals by time shifting the interference signals so that they have zero moveout, averaging a series of the cross-correlations together and subtracting the averaged cross-correlation from the cross-correlated reference signals and seismic wave sensor signals.
Claim 21
Dependent Claim
24 words
The apparatus for providing information on the subterranean geologic formation of Claim 1 in which said reference sensor is located on said drilling rig.
Claim 22
Dependent Claim
29 words
The apparatus for providing information on the subterranean geologic formation of Claim 20 in which said reference sensor comprises an accelerometer located on a swivel of said drilling rig.
Claim 23
Dependent Claim
27 words
The apparatus for providing information on the subterranean geologic formation of Claim 20 in which said drilling rig generates incoherent signals which are attentuated in the cross-correlation.
Claim 24
Dependent Claim
16 words
The apparatus of Claim 1 in which said drilling rig is located on an offshore platform.
Claim 25
Independent Claim
193 words
A method for providing information on a subterranean geologic formation, which comprises providing seismic waves with a rotary drilling bit while drilling in the earth with the rotary drilling bit, receiving in direct seismic wave paths and seismic wave paths reflected from the subterranean geologic formation the seismic waves provided by the drill bit at a location in the earth spaced from the rotary drilling bit, receiving the seismic waves proximate to a drilling rig connected to the rotary drilling bit, cross-correlating the seismic signals sensed proximate to the drilling rig and spaced from the drilling rig to separate the drill bit generated signals from interference signals by combining the reference signals and the signals received spaced from the drilling rig, and separating the cross-correlated reference signals and the signals received spaced from the drilling rig into a first group of the drill bit generated seismic signals travelling to the at least one location spaced from the drilling rig in direct paths and a second group of the drill bit generated seismic signals travelling to the at least one location spaced from the drilling rig in paths reflected from the subterranean geologic formation.
Claim 26
Independent Claim
193 words
A method for providing information on a subterranean geologic formation, which comprises providing seismic waves with a rotary drilling bit while drilling in the earth with the rotary drilling bit, receiving in direct seismic wave paths and seismic wave paths reflected from the subterranean geologic formation the seismic waves provided by the drill bit at a location in the earth spaced from the rotary drilling bit, receiving the seismic waves proximate to a drilling rig connected to the rotary drilling bit, cross-correlating the seismic signals sensed proximate to the drilling rig and spaced from the drilling rig to separate the drill bit generated signals from interference signals by combining the reference signals and the signals received spaced from the drilling rig, and separating the cross-correlated reference signals and the signals received spaced from the drilling rig into a first group of the drill bit generated seismic signals travelling to the at least one location spaced from the drilling rig in direct paths and a second group of the drill bit generated seismic signals travelling to the at least one location spaced from the drilling rig in paths reflected from the subterranean geologic formation.
Claim 27
Dependent Claim
36 words
The method for providing information on the subterranean geologic formation of Claim 24 in which the direct and reflected seismic waves are received by a plurality of sensors located proximate to a surface of the earth.
Claim 28
Dependent Claim
36 words
The method for providing information on the subterranean geologic formation of Claim 24 in which the direct and reflected seismic waves are received by a sensor positioned in a borehole spaced from said rotary drill bit.
Claim 29
Dependent Claim
22 words
The method for providing information on the subterranean geologic formation of Claim 24 additionally comprising the step of deconvolving the reference signals.
Claim 30
Dependent Claim
33 words
The method for providing information on the subterranean geologic formation of Claim 27 in which the reference signal deconvolving step provides an approximation to an inverse of the reference signals reversed in time.
Claim 31
Dependent Claim
49 words
The method for providing information on the subterranean geologic formation of Claim 24 additionally comprising the step of attenuating interference signals generated by said drilling rig from the seismic wave sensor signals based on moveout differences between the interference signals and the drill bit generated seismic wave sensor signals.
Claim 32
Dependent Claim
40 words
The method for providing information on the subterranean geologic formation of Claim 24 additionally comprising the step of converting the reference signals to signals corresponding to the seismic waves generated by the drill bit by time shifting the reference signals.
Claim 33
Dependent Claim
33 words
The method for providing information on the subterranean geologic formation of Claim 30 in which the reference signals are time shifted after cross-correlation of the reference signals and the seismic wave sensor signals.
Claim 34
Dependent Claim
40 words
The method for providing information on the subterranean geologic formation of Claim 24 in which the seismic wave sensor signals are separated into the first and second groups on the basis of moveout differences between the first and second groups.
References Cited (Backward Citations)
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