Reflection Impedance

AVO is now an established technology and has been <br>widely deployed as a lithology indicator and also as a <br>direct hydrocarbon indicator. In recent years this <br>technology has become a routine processing and its <br>application to large 3D volumes has relied on the use <br>of near- and far-offset stack volumes. These volumes <br>greatly reduce the amount of pre-stack information <br>that needs to be stored for standard AVO processing. <br>Additionally, these volumes are easily converted into <br>usual AVO attributes, like intercept and gradient, <br>which can then be interpreted in terms of anomalies <br>and calibrated with well logs. Reservoir <br>characterization studies make use not only of these <br>traditional AVO attributes but also impedance <br>volumes. The near-offset, or the intercept, stack <br>volume offers a natural way of obtaining acoustic <br>impedance volume through the use of post-stack <br>inversion algorithms. However, to invert far-stack <br>volume one needs an approach capable of estimating <br>impedances for a variable incidence angle. This <br>approach has been described in the elastic impedance <br>function presented by Connolly (1999). In this work <br>we propose an approach called reflection impedance, <br>which is based on constant ray parameter and a power <br>relationship between density and S-wave velocity. <br>This new method proved to be of better accuracy for <br>angular impedance estimation and reflection <br>coefficient recovery when compared with the elastic <br>impedance approach.