The synthetic example is based on a field data set from the Gulf of Mexico. A well was drilled on location which hit gas, and was logged for sonic velocity and density. The reservoir level is at about 2.960 km depth, and the reservoir sand dips 5-10. The target zone chosen to perform the Kirchhoff elastic prestack depth migration/inversion is a 2x2 km image area, which is 1.75-3.75 km in depth (1.5-3.0 seconds on the stacked time section).
A synthetic shot gather was calculated based on a 1-D estimate of the true earth model at this site, as shown in Figure . The synthetics were generated by the paraxial raytracing algorithm PRX87 (Beydoun, 1985, Beydoun and Keho, 1987). The shot gather contains primaries only (no multiples) and includes the amplitude effects of 3-D geometrical divergence, elastic reflection/transmission loss, and high frequency anelastic Q attenuation (but not dispersion). We used a 25 Hz peak frequency zerophase Ricker wavelet to simulate the source waveform.
The 1-D elastic
model properties are given in Table 1, and plotted in Figure .