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Results
ABSTRACT 3-D migration deconvolution (MD) was successfully applied to prestack migration data in both the time and depth domain. Test results show that migration deconvolution yields improvement in migration image quality by increasing spatial resolution and correcting for irregular illumination. In some results of MD images, new fault pathways are revealed clearly. There is, typically, better resolution improvement at shallow depths than at deeper horizons. This is to be expected from the resolution limits imposed by Fresnel zone physics.
- Research Report > New Finding (0.35)
- Research Report > Experimental Study (0.35)
ABSTRACT The feasibility of using seismic long offsets for imaging targets located below complex overburden is investigated by using synthetic modeling procedures based on a real geologic model of the central Apennines, Italy. Illumination through ray tracing, acoustic modeling and depth imaging through PSDM are the techniques used. The results indicate that extended offsets up to two times the depth of the target can be successfully used for imaging without introduction of artifacts and that the imaging results are substantially better than those obtained with a conventional seismic layout.
- Europe > Italy (0.24)
- North America > United States > Colorado (0.17)
- Geophysics > Seismic Surveying > Seismic Processing (1.00)
- Geophysics > Seismic Surveying > Seismic Modeling > Velocity Modeling (0.48)
A velocity/depth model from a seismic data set was used together with the P1/90 navigation data to estimate the subsurface illumination and the migration amplitudes along key horizons. These simulated migration amplitudes can be generated during the acquisition to assess the need for infill shooting. Introduction Coverage specifications are believed to ensure the successful completion of a 3D survey. Since there is less control over the lateral position of the tail of the streamer than the front-end, specifications for the large offsets are normally looser. These specifications are in terms of source-receiver midpoint hits per offset-group per bin. Lateral and vertical changes in the subsurface velocity field Figure 1: Inline through the data set may give rise to ray bending, which in turn influences the illumination at target horizons. Hence, a uniform coverage NORSAR's ray trace modelling was used to calculate the at the surface does not guarantee a uniform coverage or impact of both real and imaginary (no feathering) illumination at subsurface interfaces.
- Geophysics > Seismic Surveying > Seismic Processing > Seismic Migration (1.00)
- Geophysics > Seismic Surveying > Seismic Modeling > Velocity Modeling (0.91)
ABSTRACT We develop a simplified theoretical treatment of asymptotic ray-based beam inversion for common-offset. We apply the theory to the development of a true-amplitude imaging algorithm using Gaussian beams. The theoretical treatment is valid for arbitrary velocity variations, and we find that the amplitude behavior of our algorithm is reasonably close to true-amplitude common-offset Kirchhoff inversion. We give a further example of the application of our algorithm to imaging the Atlantis structure in the Gulf of Mexico (GOM). In areas where illumination is poor, asymptotic beam and Kirchhoff inversion do not apply, and migration deconvolution or dip equalization is required. We derive the form of the Hessian for common-offset Gaussian beam migration, and use it to produce inverse migration deconvolution operators for the same Atlantis GOM structure.
Some Practical Issues Related to Migration In the Angle Domain
Lipari, Vincenzo (Politecnico di Milano) | Andreoletti, Clara (ENI, E&P Division) | Bernasconi, Giancarlo (Politecnico di Milano) | Bienati, Nicola (ENI, E&P Division) | Drufuca, Giuseppe (Politecnico di Milano) | Cazzola, Luca (ENI, E&P Division)
Two angles describe the illumination dip vector - λ: Elevation of the illumination dip vector The benefits of recasting pre-stack depth migration in the - ψ: Azimuth of the illumination dip vector angle domain are such to suggest its application in industrial Kirchhoff PSDM software. Here we examine Once the scattering angles are fixed, for each depth point, some practical aspects of the implementation in the angle migration consists in the integral over dip angles, i. e. over domain, namely those that mostly impact performances and the unit ray hemisphere. This is the most natural domain for effectiveness: memory requirements, poor illumination and this integration.