Data processing: measuring – calibrating – or testing – Measurement system in a specific environment – Earth science
Reexamination Certificate
1999-03-15
2001-01-30
McElheny, Jr., Donald E. (Department: 2862)
Data processing: measuring, calibrating, or testing
Measurement system in a specific environment
Earth science
C367S075000
Reexamination Certificate
active
06182015
ABSTRACT:
BACKGROUND OF THE INVENTION
The present invention pertains to seismic data processing and more particularly to processing seismic data obtained from seismic cables set on land or under a body of water where multi-axial geophones are used at each single receiver location. The present invention pertains to changing the orientation of multicomponent seismic detectors and more particularly to the use of data manipulation and the rotation of the orientation of seismic detectors to remove errors and noise from detected data.
Multicomponent detectors are generally composed of three geophones: two orthogonal horizontal geophones and one vertical geophone. There are various problems in the orientation of these multicomponent geophone assemblies. One problem is due to shot position errors, or the location of the shot or source with respect to the detectors. A further problem occurs in marine environment. When the array is laid on the ocean bottom, various ocean floor inconsistencies, such as rocks, coral, etc., can misalign the intended orientation. Still another problem relates to coupling errors between the geophones and the earth.
There have been attempts at dealing with the determination of receiver orientation angle. However, even under these methods, there is still some error. Even if the residual error is on the order of a few degrees, it still needs to be addressed.
An example of prior art efforts to compensate for coupling discrepancies in seismic data acquisition is U.S. Pat. No. 5,724,307, incorporated herein by reference, titled “Method for Improving the Coupling Response of a Water Bottom Seismic Sensor” issued to James E. Gaiser. This reference relates to providing a receiver-consistent deconvolution operator that models the damped oscillatory wavetrain which is related to geophone coupling to the water bottom. The operator described is a best-fitting function that endeavors to describe the difference in coupling response between a well coupled first geophone relative to an imperfectly coupled second geophone. The operator is applied to the second signals to compensate the signals for the distortion due to imperfect second ground coupling.
SUMMARY OF THE INVENTION
The object of the present invention is to address the problems described above. According to one aspect of the invention, therefore, a method is provided for processing first and second seismic traces, each of the traces having a source location and a receiver location associated therewith, the method comprising: rotating the first and second traces to about an a pre-determined angle from a line between the source location and the receiver location associated with the traces; manipulating the traces at about the pre-defined angle, wherein manipulated traces result; and rotating the manipulated traces to a desired orientation.
According to a more specific embodiment, the manipulating comprises: dividing the rotated first traces into time windows; dividing the rotated second traces into time windows; and transforming the rotated and divided first time domain traces and the rotated and divided second time domain traces to the frequency domain to obtain an amplitude spectrum for each time window of the rotated first time domain trace and an amplitude spectrum for each time window of the rotated second time domain trace.
Next, the following steps are performed: squaring each the amplitude spectrum to obtain a power spectrum for each the transformed rotated first time domain trace and for each the transformed rotated second time domain trace time domain trace; averaging the power spectrum for each the transformed rotated first time domain window across a common receiver gather; averaging the power spectrum for each the transformed rotated second time domain window across a common receiver gather; defining a third power spectrum representing a source wavelet, dependant upon the averaging; dividing the third power spectrum by the first power spectrum to obtain a set of first frequency domain scalars; dividing the third power spectrum by the second power spectrum to obtain a set of second frequency domain scalars; and determining the amplitude spectrum of the rotated first and second traces, wherein an first amplitude spectrum results, a second amplitude spectrum results, an first phase spectrum results, and a second phase spectrum results.
The process then continues with: multiplying the first amplitude spectrum by the set of first frequency domain scalars; multiplying the second amplitude spectrum by the set of second frequency domain scalars; inverse transforming the first amplitude spectrum multiplied by the set of first frequency domain scalars using the first phase spectrum; inverse transforming the second amplitude power spectrum multiplied by the set of second frequency domain scalars using the second phase spectrum; comparing amplitudes of the inverse transformed first amplitude spectra multiplied by the set of first frequency domain scalars to derive an first amplitude scalar; and comparing amplitudes of the inverse transformed second amplitude spectra multiplied by the set of second frequency domain scalars to derive a second amplitude scalar.
The process finishes with: matching the amplitude of the entire trace to a predetermined constant with the first amplitude scalar to obtain an amplitude and wavelet matched trace; matching the amplitude of the entire trace to a predetermined constant with the second amplitude scalar to obtain an amplitude and wavelet matched trace; and re-rotating the traces to a desired orientation.
Further, in one even more specific embodiment, the re-rotating step includes: returning the traces to original orientation; and determining wavelet matched traces by inverse transformation. In still a further embodiment, the rotating step includes: returning the traces to original orientation; and determining wavelet matched traces by deconvolution.
According to another aspect of the invention, a further method is provided for processing multicomponent seismic data, wherein the data comprises traces from a first component and a second component, wherein there is a source location and a receiver location associated with each trace, the method comprising: determining an angle between one of the axes of either the first component or the second component; assigning a ratio value to an amplitude relationship between the first and the second components, the value being dependant upon the angle; determining an actual ratio of the amplitudes of the first component and the second component; deriving at least one scalar dependant upon the value and the actual ratio such that multiplication of the at least one scalar and at least one of the traces of first component and the second component causes the ratio of the multiplied trace amplitude and the amplitude of the trace from the other component to match the value; and multiplying the at least one scalar to at least one of the traces of the first component and the second component.
In a more specific example embodiment, the method further comprises rotating the traces.
In still a further aspect of the present invention, a method is provided for processing multicomponent seismic data, wherein the data comprises traces from a first component and a second component, wherein there is a source location and a receiver location associated with each trace, the method comprising: rotating the traces to a predetermined angle between one of the axes of either the first component or the second component; assigning a ratio value to an amplitude relationship between the first and the second components, the value being dependant upon the angle; determining an actual ratio of the amplitudes of the first component and the second component; deriving at least one scalar dependant upon the value and the actual ratio such that multiplication of the at least one scalar and at least one of the traces of first component and the second component causes the ratio of the multiplied trace amplitude and the amplitude of the trace from the other component to match the value; and mu
Altan Suat
Li Jianchao
Zhu Xianhuai
Arnold & Associates
McElheny Jr. Donald E.
PGS Tensor Inc.
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