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17.4.1 SALT Program

The salt program generates a velocity data file for the seismic and revtime programs. Some of the truly interesting geological structures are those made by salt and are typically found in the Gulf of Mexico. salt computes a salt body model; the principal feature is the high velocity contrast between the salt and the surrounding geological media. This particular salt model is an intrusion, a slowly moving feature pushing up and aside the inplace media; these geological changes take millions of years to form. The regions near the salt which are lifted or tilted make excellent reservoirs. The velocities of this model have maximum to minimum ratio of 4. A portion of the saltv.f program listing is shown in PROGRAM CODE IV.

Subsalt exploration is receiving considerable attention, and the imaging of subsalt geological structures is becoming a more routine process. Two difficulties of subsalt imaging are the roughness of the top of the salt layer and the small reflection coefficients. The roughness scatters the incoming wave field, and the small reflection coefficient keeps energy from reflecting. Both of these mechanisms reduce the amount of available energy for reflections.

PROGRAM CODE IV, a portion of saltv.f --- View code