S-wave Velocity Prediction by Using Critical Porosity Model and Gassmann Equations

Abstract

S-wave velocity is very important in seismic interpretation, especially in AVO modeling, but in practice S-wave velocity is often not recorded, or even if is available but in poor quality. There are many methods to estimate S-wave velocity, including both empirical relationships and theoretical formulae. This paper proposed a new method to predict S-wave velocity by combining critical porosity model and Gassmann equations. Different from the usual critical porosity model, we first obtained a critical porosity value by inverting P-wave velocity, and applied it to predict S-wave velocity. The applications of experiment and logging data both indicate that this new method can reduce uncertainty brought by selecting the empirical critical porosity value in the past, and provide the accurate critical porosity value for predicting S-wave velocity, which significantly improved the prediction accuracy.