Introduction

Depending on how we approach the problem of well-to-well correlation, we can get different matching results, which can in turn reflect different geological aspects and be related to distinct geophysical images. As observed by several authors (Vail et al., 1977; Sangree and Widmier, 1979), seismic sections represent a chrono-structural image of the earth, whereas the slowness values that are measured in a sonic log are more closely related to lithologic units.

If we choose a smoothed version of the sonic log as the matching attribute, the resulting correlation might be used as a suitable constraint or as an initial model for the tomographic inversion of seismic-traveltime data. However, if we wish to find a correlation between these logs that would correspond to the continuous reflector seen in a surface seismic section, we have to look for an attribute with a chronological (instead of a lithological) meaning. Although synthetic seismograms are the natural attribute candidates for performing the ``seismic-reflection correlation" between sonic logs, it is possible to construct other attributes that can better represent the different sequences of events represented in the logs and, therefore, be more suitable for reproducing the ``feeling of continuity" of a seismic section.