AVO Anomaly Class Detection and Hydrocarbon Identification Using the Attributes of Intercept, Gradient and Changes in Poissonꞌs Ratio with their Crossplots

In petroleum industry, results from changes in seismic waves reflection amplitude versus offset can be used in extracting elastic properties and hence lithology and pore fluids identification in reservoirs. AVO analysis is one of the quantitative study methods related to seismic data which is applied on pre-stack data. Before performing AVO analysis studies, processing steps accuracy should be ensured so that changes in reflection amplitude will be only relative to changes in elastic properties of layers. One of the major parts of AVO analysis is investigation of common AVO attributes such as AVO intercept, AVO gradient and Poisson’s ratio or a combination of them. The cross plot method which compares two attributes simultaneously can play an efficient role in AVO analysis. In this study, AVO analysis is executed on a loose and unconsolidated sand stone reservoir and well logging data were used to calibrate real seismic data. Fluid Replacement Modeling (FRM) using well data and Gassmann’s equation showed that AVO behavior in every conditions of reservoir (with changes in fluid type and fluid saturation percentage) belongs to class IV of Rutherford and William’s classification which is in consistent with real data. The hydrocarbon boundary in seismic data which is obtained using attributes, their cross plots and also attributes plotting as structural sections of estimation considered horizon are in accordance with gained location from well data.