ABSTRACT

A borehole sonic log (with some effects of density) and a seismic trace are both signal carriers of the same geological information, but with different emphasis. Whereas the sonic log provides a continuous profile of the rocks that make up the sedimentary section, the seismic trace principally describes the contact boundaries between adjacent, different geological units.

Thus the interpretation of seismic sections tends to emphasize the structure and morphology of rock units at the expense of other information. Fortunately, these differences can be described mathematically and compensated for within the constraints of resolution and the information-carrying capacity of seismic and sonic log signals.

In addition to structure, information regarding lithology, porosity and maturation parameters of sedimentary rocks can all be derived from seismic reflection data with some greater or lesser degree of certainty. In one example, the use of such methods resulted in the ability to separate and predict the contributions of faulting, facies changes, structure and erosion to variations in recovery from a large petroleum reservoir and thereby assist in the design of an optimum program for enhanced production and extension to the field.

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