An integrated approach to the analysis of amplitude variation with offset in Vertical Transversely Isotropic (VTI) media using inclusion-based rock physics modeling

For accurate lithology and fluid content characterization from the amplitude with offset analysis in hydrocarbon fields, understanding the shale anisotropy effect on reflectivity is essential. Shale-rich sedimentary deposits are common components of sedimentary sequences with strong anisotropic properties. The main objective of this study is to perform anisotropic AVO analysis in vertical transversely isotropic (VTI) media at the top of a shale/gas sand interface, utilizing inclusion-based rock physics modeling in the Burgan formation in an Iranian oilfield. Results have shown that anisotropic AVO analysis shows Class I AVO which is indicative of the presence of hydrocarbon, whereas isotropic AVO analysis has shown no trend of any AVO classes. This study also investigates the application of a rock physics template in the shalegas- sand interface in the Burgan formation. Without rock physics modeling, gas-sand can not be detected using the P- to S-wave velocity ratio against an acoustic impedance cross- plot. After rock physics modeling, gas sand has been discriminated from shale with a low P- to S-wave velocity ratio, low acoustic impedance, and high effective porosity in this cross-plot.
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