Diffraction imaging using pseudo dip-angle gather
AssigneeSaudi Arabian Oil Company
InventorsLu Liu, Yi Luo, Tong Wang Fei
Life of this patent
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Abstract
Systems, methods, and apparatuses for generating a subsurface image using diffraction energy information are disclosed. The systems, methods, and apparatuses may include converting a shot gather into one or more plane-wave gather using a Radon transform. The plane-wave gathers may be extrapolated into source-side wavefields and receiver-side wavefields and further generate a pseudo dip-angle gather. The diffraction energy information may be extracted from the pseudo dip-angle gather, and an image containing subsurface features may be generated from the extracted diffraction energy information. The receiver-side wavefields may be decomposed using a recursive Radon transform.
Claims14
A computer-implemented method performed by one or more processors for generating an image of subsurface features of a portion of the earth using diffraction energy, the method comprising the following operations:
- receiving a shot gather formed from a plurality of shots;
- converting the shot gather into one or more plane-wave gathers based on the following equation:
- Ur(xrt;p)=∫ur(xs,t+p(xs−x0);xr)dxs,
- where p is a ray parameter obtained by sin(θ0) /v0, θ0 is a surface incident angle that is measured from a z-axis to an initial direction of plane-wave propagation, v0 is a surface velocity, x0 represents a plane-wave origin at a surface, xs and xr represent source and receiver locations, respectively, t represents time, ur(xs,t;xr) represents the shot gather prior to conversion, and Ur(xr,t;p) represents the plane-wave gathers after the conversion;
- selecting one of the plane-wave gathers;
- extrapolating source-side wavefields of the plane-wave gather downward;
- extrapolating receiver-side wavefields of the plane-wave gather downward and decomposing the extrapolated receiver-side wavefields, wherein decomposing the receiver-side wavefields of the plane-wave gather comprises applying a recursive Radon transform to the receiver-side wavefields of the plane-wave gather;
- forming a pseudo dip-angle gather by applying an imaging function to the extrapolated plane-wave source-side wavefields and the decomposed plane-wave receiver-side wavefields;
- extracting the diffraction image information from the pseudo dip-angle gather by using a windowed median filter;
- and
- generating a stacked diffraction image representative of subsurface features of a portion of the earth, wherein the stacked diffraction image is used in well design to access a reservoir.
A computer program product encoded on a non-transitory medium, the computer program product comprising computer readable instructions for causing one or more processors to perform operations comprising:
- receiving a shot gather formed from a plurality of shots;
- converting the shot gather into one or more plane-wave gathers by using a linear Radon transform based on the following equation:
- Ur(xr,t;p)=∫ur(xs,t+p(xs−x0);xr)dxs,
- where p is a ray parameter quantified by sin(θ0) /v0, θ0 is a surface incident angle that is measured from a z-axis to an initial direction of plane-wave propagation, v0 is a surface velocity, x0 represents a plane-wave origin at a surface, xs and xr represent source and receiver locations, respectively, t represents time, ur(xs,t;xr) represents the shot gather prior to conversion, and Ur(xr,t;p) represents the plane-wave gathers after the conversion;
- selecting one of the plane-wave gathers;
- extrapolating source-side wavefields of the plane-wave gather downward;
- extrapolating receiver-side wavefields of the plane-wave gather downward and decomposing the extrapolated receiver-side wavefields, wherein decomposing the receiver-side wavefields of the plane-wave gather comprises applying a recursive Radon transform to the receiver-side wavefields of the plane-wave gather;
- forming a pseudo dip-angle gather by applying an imaging function to the extrapolated plane-wave source-side wavefields and the decomposed plane-wave receiver-side wavefields;
- extracting the diffraction image information from the pseudo dip-angle gather by using a windowed median filter;
- and
- generating a stacked diffraction image representative of subsurface features of a portion of the earth, wherein the stacked diffraction image is used in well design to access a reservoir.
An apparatus for generating an image of subsurface features using diffraction energy information comprising:
- one or more processors;
- and
- a non-transitory computer-readable storage medium coupled to the one or more processors and storing programming instructions for execution by the one or more processors, the programming instructions operable to instruct the one or more processors to:
- receiving a shot gather formed from a plurality of shots;
- converting the shot gather into one or more plane-wave gathers based on the following equation:
- Ur(xr,t;p)=∫ur(xs,t+p(xs−x0);xr)dxs,
- where p is a ray parameter quantified by sin(θ0) /v0, θ0 is a surface incident angle that is measured from a z-axis to an initial direction of plane-wave propagation, v0 is a surface velocity, x0 represents a plane-wave origin at a surface, xs and xr represent source and receiver locations, respectively, t represents time, ur (xs,t;xr) represents the shot gather prior to conversion, and Ur(xr,t;p) represents the plane-wave gathers after the conversion;
- selecting one of the plane-wave gathers;
- extrapolating source-side wavefields of the plane-wave gather downward;
- extrapolating receiver-side wavefields of the plane-wave gather downward and decomposing the extrapolated receiver-side wavefields, wherein decomposing the receiver-side wavefields of the plane-wave gather comprises applying a recursive Radon transform to the receiver-side wavefields of the plane-wave gather;
- forming a pseudo dip-angle gather by applying an imaging function to the extrapolated plane-wave source-side wavefields and the decomposed plane-wave receiver-side wavefields;
- extracting the diffraction image information from the pseudo dip-angle gather by using a windowed median filter;
- and
- generating a stacked diffraction image representative of subsurface features of a portion of the earth, wherein the stacked diffraction image is used in well design to access a reservoir.
Dependencies are inferred from the claim text.