Communications – electrical: acoustic wave systems and devices – Seismic prospecting – Land-reflection type
Patent
1995-10-20
1997-01-21
Lobo, Ian J.
Communications, electrical: acoustic wave systems and devices
Seismic prospecting
Land-reflection type
367 50, G01V 136, G01V 128
Patent
active
055965474
ABSTRACT:
A method of prestack time migration based on the principles of prestack Kirchhoff time migration that can be applied to both 2-D and 3-D data. Common scatter point (CSP) gathers are created as an intermediate step for each output migrated trace. Normal moveout (NMO) and stacking of CSP gathers is performed to complete the prestack migration process. The method of the present invention allows the CSP gathers to be formed at any arbitrary location for velocity analysis, or to prestack migrate a 2-D line from a 3-D volume. The CSP gather is similar to a CMP gather as both contain offset traces, and both represent a vertical array of scatter points or reflectors. The CSP gather is formed from all the input traces within the migration aperture. Samples in the input traces are assigned an equivalent offset for each CSP location, then copied into the appropriate offset bin of the CSP gather in an efficient manner. The input time samples remains at the same time when copied to the CSP gather. Data in the CSP gathers may be scaled, filtered, or have noise attenuation processes applied. The equivalent offset may be derived in a simplified form as a combination NMO and post-stack migration or in a more complex form based on the double square root (DSR) equation of prestack migration. The prestack migration form of the CSP gather enables it to correctly image scattered and dipping events prior to NMO. The prestack nature, high fold, and large offsets aid in providing a better focus of the semblance plot for an improved velocity analysis.
REFERENCES:
patent: 5500832 (1996-03-01), Berryhill
G. H. F. Gardner, et al., "Dip Moveout and Prestack Imaging", 1986 Offshore Technology Conference, pp. 75-83.
David Forel et al., "A Three-Dimensional Perspective on Two-Dimensional Dip Moveout", Geophysics, vol. 53, No. 5, May 1988, pp. 604-610.
Philip S. Schultz et al., "Depth Migration Before Stack", Geophysics, vol. 45, No. 3, Mar. 1980, pp. 376-393.
J. W. Sattlegger et al., "Common Offset Plane Migration (COPMIG)", Geophysical Prospecting, 1980, pp. 859-871.
S. M. Deregowski, "Common-Offset Migrations and Velocity Analysis", First Break, vol. 8, No. 6, Jun. 1990, pp. 225-234.
J. P. Diet et al., "Velocity Analysis with Prestack Time Migration Using the S-G Method: A Unified Approach", Seismic Modeling/Migration 5: Migration Velocities/3-D Migration, Sep. 29th, pp. 957-960.
Ozdogan Yilmaz, "Seismic Data Processing", Society of Exploration Geophysicists, pp. 331-335 and 507-518.
Bancroft John C.
Geiger Hugh D.
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