Aprendendo a confiar em Greenberg-Castagna

Greenberg and Castagna’s (1992) technique of shear-sonic construction using Vp data, is a lithology based regression which uses the Gassman equation. As an empirical relation, it should apply only to the set of rocks that generated it. But is seems to be more robust than initially imagined. The Greenberg-Castagna method was used to predict Vs in six wells from different Brazilian Basins. The analysis suggests that the method is applicable for most part of the data. Despite some good results showed here, it should always be used with a full understanding of its assumptions and limitations. It is hoped that the ideas presented herein may lead to a better understanding of the technique, and to reduce uncertainty in its application.