Ray tracing computations in the smoothed Salt Model

Source at the surface - history file 'sal-ray1.h'

This is an example of two-parametric ray tracing in smoothed Salt Model with the most important interfaces. Velocity model is specified in the file 'sal-mod2.dat'. The model is version with the most important interfaces: the ocean bottom, the interfaces limiting the salt body, the geopressure horizon and the bottom flat interface. Generation of the selected and other smooth versions of SEG/EAGE Salt Model is described in Building the Salt Model by inversion. Model 'sal-mod2.dat' is an output of history file 'sal-inv2.h'. The name of the model output file was changed from the 'sal-m2.out' to 'sal-mod2.dat'.

Computation is performed for one shot in the depth of 20m at the centre of 21x21 receivers square located in the depth of 0m. The receiver grid step is 320m. The position of the shot above the salt crest is similar to the original SEG/EAGE Phase A Acquisition where this point is the intersection of two 3-D shot lines (Aminzadeh et al. 1997). Rays of refracted P-wave and P-waves reflected from top and bottom interfaces of salt and bottom interface are computed. Synthetic seismograms for selected profile are generated and plotted. History file 'sal-ray1.h' adds rays, receivers and source into GOCAD file.

For more information about this computation see Bucha (2003).

Sources in the well - history files 'sal-rwe1.h', 'sal-rwe2.h'

This is an example of two-parametric ray tracing in smoothed Salt Model with the most important interfaces. Velocity model is the same as in the part describing the use of history file 'sal-ray1.h'. Computation is performed for two shots in a well. One shot is located above the salt body in the depth of 900m and the other shot is located below the salt body in the depth of 2300m. The square of 21x21 receivers is located in the depth of 0m. The receiver grid step is 320m. The positions of the shot-receiver configurations are derived from the original SEG/EAGE Phase A Acquisition (Aminzadeh et al. 1997). Rays of refracted P-wave and P-waves reflected from top and bottom interfaces of salt and bottom interface are computed. Rays from the shot below the salt include multiple reflections. Synthetic seismograms for selected profile are generated and plotted. History files 'sal-rwe1.h' and 'sal-rwe2.h' add rays, receivers and shots into GOCAD file.

For more information about this computation see Bucha (2004a).

Maps of reflections - history file 'sal-mapx.h'

History file 'sal-mapx.h' computes two-point rays of the P-wave reflected from the flat bottom interface in the smoothed SEG/EAGE Salt Model. Velocity model is the same as in the part describing the use of history file 'sal-ray1.h'. Six shot-receiver configurations derived from the original Phase A Acquisition are used for generation of reflection point maps, colour coded according to amplitudes. History file 'sal-mapx.h' executes step by step six other history files 'sal-map1.h', 'sal-map2.h', 'sal-map3.h', 'sal-map4.h', 'sal-map5.h', 'sal-map6.h'. Each of these six history files can be executed separately. Shots are located in the depth of 20m and the step is 800m. Receivers are located in the depth of 0m and the grid step is 320m. Computed rays, reflection maps, receivers and sources are added into GOCAD file.

For more information about this computation see Bucha (2004b).

References

Aminzadeh, F., Brac, J., Kunz, T. (1997): 3-D Salt and Overthrust Models. SEG/EAGE 3-D Modeling Series No.1., Soc. Explor. Geophysicists, Tulsa.

Bucha, V. (2003): Ray tracing computations in the smoothed Salt Model. In: Seismic Waves in Complex 3-D Structures, Report 13, pp. 239-246, Dep. Geophys., Charles Univ., Prague.

Bucha, V. (2004a): Ray tracing computations in the smoothed Salt Model. Part 2: Sources in the well. In: Seismic Waves in Complex 3-D Structures, Report 14, pp. 27-34, Dep. Geophys., Charles Univ., Prague.

Bucha, V. (2004b): Ray tracing computations in the smoothed Salt Model. Part 3: Maps of reflections. In: Seismic Waves in Complex 3-D Structures, Report 14, pp. 35-42, Dep. Geophys., Charles Univ., Prague.