The amplitude variation with offset (AVO) technique as a direct hydrocarbon indicator

Abstract

The amplitude variation with offset (A VO) technique in seismic exploration was introduced about twenty years ago. In the following years, the technique has evolved from a concept to a primary component of seismic exploration. This method has shown to indicate the presence of gas sands if the reflection amplitude increases rapidly with increasing shot-to-geophone (or hydrophone) distance. Moreover, a deviation from a background trend, formed when crossplotting the A VO intercept and the A VO gradient, may be seen as anomalous and could be a hydrocarbon indicator. Prediction of the fluid and reservoir quality prior to drilling, using this technique, reduces the risk of drilling high-risk wells. The theory of the A VO method is discussed in this dissertation and it is shown how it can add reliable constraints to quantitative reservoir characterization if the operator understands the underlying concepts on how to apply the technique. The AVO method is performed on real data, gathered from offshore northern part of Malta in 1988, in a section where anomalies are apparent in the data obtained from the survey. Conclusions on the nature of the pore-fill of the rock were drawn by the interpretation of crossplots.