Application of AVO Attributes and Fluid Replacement in Determining AVO Anomaly; Case Study of Aboozar Oil Field, Iran

AVO analysis is a technique which is widely used in industry and is applied on seismic prestack data. Results from changes in seismic wave reflection amplitude versus offset can be used in extracting elastic properties and hence lithology and reservoirs pore fluid identification. Before performing AVO analysis studies, processing steps should be ensured that changes in reflection amplitude are relative to only 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 scaled Poisson’s ratio and their combinations. The crossplot of AVO attributes can play an efficient role in AVO analysis. In this research, AVO analysis is executed on a loose and unconsolidated sandstone reservoir and also well logging data were used to calibrate real seismic data. By using Fluid Replacement Modeling (FRM) and Gassmann’s equation on reservoir well data, AVO behavior in every conditions of reservoir (with changes in fluid type and saturation) shows that it belongs to class IV of Rutherford and William’s classification. Moreover, hydrocarbon zones which are defined using applying AVO attributes on cross-sections and target horizon, are found consistent with information from well data.