Perfis Sintéticos De Vs: Greenberg Castagna X Redes Neurais

Advantages of using shear waves have already been<br>known for a long time, specially when used together<br>with compressinal waves. Applications include wellbore<br>stability analysis, gas detection, evaluation of<br>formation anisotropy, interpretation and calibration<br>of AVO analysis. Specifically with AVO modelling,<br>when shear-wave logs are not available or when<br>doubts about log accuracy arise, it is possible to predict<br>the Vs logs using some of the models published<br>in literature. In this paper, using data from two offshore<br>wells, we compare the performance of two<br>models for predicting Vs: the well-known Greenberg-<br>Castagna and an artificial neural networks method<br>named backpropagation. Each method showed advantages<br>and limitations and depending on the quality of<br>preliminary information available one of the methods<br>can prevail over the other.