Method for depth imaging multicomponent seismic data
First Claim
1. A method of geophysical exploration to obtain depth images of the earth'"'"'s subsurface geological structures, comprising the steps of:
- (a) obtaining separate measures of compressional and shear wavefields incident on reflecting interfaces in the earth'"'"'s subsurface;
(b) obtaining measures of compressional and shear wavefields scattered from the reflecting interfaces;
(c) producing time-dependent reflectivity functions representative of the reflecting interfaces from the compressional and shear wavefields incident thereon and the compressional and shear wavefields scattered therefrom; and
(d) migrating the time-dependent reflectivity functions to obtain depth images of the reflecting interfaces in the earth'"'"'s subsurface.
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Abstract
The present invention relates generally to a method of geophysical exploration and more particularly to a novel method for imaging multicomponent seismic data to obtain better depth images of the earth'"'"'s subsurface geological structure as well as better estimates of compressional and shear wave interval velocities. In particular, measures are obtained of imparted seismic wavefields incident on reflecting interfaces in the earth'"'"'s subsurface and of resulting seismic wavefields scattered therefrom. The incident and scattered seismic wavefields are employed to produce time-dependent reflectivity functions representative of the reflecting interfaces. By migrating the time-dependent reflectivity functions, better depth images of the reflecting interfaces can be obtained. For a dyadic set of multicomponent seismic data, the dyadic set of multicomponent seismic data are partitioned so as to separate the variously coupled incident and reflected wavefields in the recorded multicomponent seismic data. The incident and reflected wavefields are cross-correlated to form time-dependent reflectivity functions. The time-dependent reflectivity functions are then iteratively migrated according to a model of wavefield velocities of propagation to obtain better estimates of the compressional and shear wave interval velocity. The migrated reflectivity functions can then be stacked to produce better depth images of the earth'"'"'s subsurface geological structures.
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Citations
31 Claims
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1. A method of geophysical exploration to obtain depth images of the earth'"'"'s subsurface geological structures, comprising the steps of:
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(a) obtaining separate measures of compressional and shear wavefields incident on reflecting interfaces in the earth'"'"'s subsurface; (b) obtaining measures of compressional and shear wavefields scattered from the reflecting interfaces; (c) producing time-dependent reflectivity functions representative of the reflecting interfaces from the compressional and shear wavefields incident thereon and the compressional and shear wavefields scattered therefrom; and (d) migrating the time-dependent reflectivity functions to obtain depth images of the reflecting interfaces in the earth'"'"'s subsurface. - View Dependent Claims (2, 3, 4)
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5. A method of imaging multicomponent seismic data to obtain depth images of the earth'"'"'s subsurface geological structures, comprising the steps of:
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(a) beam forming the multicomponent seismic data into sets of plane wave seismograms; (b) partitioning the plane wave seismograms into sets of compressional and shear wavefield seismograms; (c) forming time-dependent reflectivity functions from the sets of compressional and shear wavefield seismograms; and (d) migrating the time-dependent reflectivity functions to obtain depth images of the earth'"'"'s subsurface geological structures. - View Dependent Claims (6, 7, 8, 9, 27)
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10. A method for imaging the earth'"'"'s subsurface geological structures, comprising the steps of:
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(a) collecting a set of multicomponent seismic data with seismic sources having at least one linearly independent line of action and receivers having at least two linearly independent lines of action; (b) sorting the set of multicomponent seismic data into incident angle ordered gathers; (c) partitioning the incident angle ordered gathers of the set of multicomponent seismic data into compressional and shear wavefields; and (d) migrating the compressional and shear wavefields to obtain a depth image of the earth'"'"'s subsurface geological structures. - View Dependent Claims (11, 12, 13, 14, 15, 16, 28)
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17. A method for imaging the earth'"'"'s subsurface geological structures, comprising the steps of:
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(a) collecting a set of multicomponent seismic data; (b) partitioning the set of multicomponent seismic data so as to separate and decouple compressional and shear wavefield potentials in the set of multicomponent seismic data; (c) iteratively migrating the separated and decoupled compressional and shear wavefields for a plurality of assumed compressional and shear interval velocities; and (d) selecting from the plurality of assumed compressional and shear wave and shear interval velocities, the compressional interval velocities which produce coherent migrated wavefields. - View Dependent Claims (18, 19, 20)
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21. A method of geophysical exploration to obtain depth images of the earth'"'"'s subsurface geological structures from multicomponent seismic data Uij, wherein seismic energy is imparted into the earth with seismic sources having at least one linearly independent line of action i and the earth'"'"'s response thereto is recorded by receivers having at least two linearly independent lines of action j, comprising steps of:
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(a) obtaining separate measures of compressional and shear wavefields generated by the seismic energy imparted into the earth which are incident on reflecting interfaces in the earth'"'"'s subsurface; (b) obtaining separate measures of compressional and shear wavefields scattered from reflecting interfaces in the earth'"'"'s subsurface from the multicomponent seismic data Uij ; and (c) migrating the incident and scattered compressional and shear wavefields to obtain depth images of the earth'"'"'s subsurface geological structures. - View Dependent Claims (22, 23, 29)
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24. A method of imaging multicomponent seismic data Uij, wherein seismic energy is imparted into the earth with seismic sources having at least one linearly independent line of action i and the earth'"'"'s response thereto is recorded by receivers having at least two linearly independent lines of action j, comprising the steps of:
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(a) radon transforming the multicomponent seismic data Uij ; (b) partitioning the radon transform multicomponent seismic data Uij to separate and decouple measures of compressional and shear wavefields scattered from reflecting interfaces in the earth'"'"'s subsurface; (c) partitioning the seismic energy imparted into the earth to separate the decouple measures of compressional and shear wavefields incident on the reflecting interfaces in the earth'"'"'s subsurface; and (d) migrating the compressional and shear wavefields incident on reflecting interfaces and the compressional and shear wavefields scattered from the reflecting interfaces to obtain depth images of the earth'"'"'s subsurface geological structures. - View Dependent Claims (30)
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25. A method for imaging the earth'"'"'s subsurface geological structures, comprising the steps of:
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(a) obtaining a set of multicomponent seismic data Uij, wherein seismic energy is imparted into the earth with seismic sources having at least one linearly independent line of action i and recording the earth'"'"'s response thereto with receivers having at least two linearly independent lines of action j; (b) partitioning the multicomponent seismic data Uij so as to separate and decouple compressional and shear wavefields measured by the set of multicomponent seismic data Uij and (c) migrating the separated and decoupled compressional and shear wavefields so as to obtain depth images of the earth'"'"'s subsurface geological structures. - View Dependent Claims (31)
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26. A method for imaging the earth'"'"'s subsurface geological structures with multicomponent seismic data Uij, wherein the multicomponent seismic data Uij is obtained by imparting seismic energy into the earth with seismic sources having at least one linearly independent line of action i and recording the earth'"'"'s response thereto with receivers having at least two linearly independent lines of action j, comprising the steps of:
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(a) radon transforming the multicomponent seismic data Uij to obtain sets of plane wave seismograms, wherein each set of plane wave seismograms includes plane wave seismograms for a plurality of incident angles; (b) partitioning each set of plane wave seismograms to separate and decouple compressional and shear wavefields scattered from reflecting interfaces in the earth'"'"'s subsurface; (c) partitioning the seismic energy imparted into the earth to separate and decouple measures of compressional and shear wavefields incident on reflecting interfaces in the earth'"'"'s subsurface (d) cross correlating the incident and reflecting compressional and shear wavefields to obtain a plurality of time-dependent reflectivity functions; and (e) iteratively migrating the plurality of time-dependent reflectivity functions for a plurality of compressional and shear wavefield interval velocities to determine the compressional and shear wavefield interval velocities which produce spatially consistent depth images.
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Specification