The Application of Amplitude Variation with Frequency (AVF) Seismic Attribute to Map Gas Saturation Values in low Impedance Sandstone Reservoirs

This paper discusses an approach to apply Amplitude Variation with Frequency (AVF) attributes for identifying and mapping gas-saturation values (Sg) in low impedance sand reservoirs. Rock-physics modelling and analyses were done prior to application of the approach to the log and seismic data in the Sadewa field, Kutai Basin, Kalimantan, Indonesia. Cross-plot sensitivity analysis shows that the AV F attribute derived from near-angle stacked seismic data is correlated linearly to the gas saturation value with correlation coefficient 0.94. Comparison of AVO-based density and AVF-based gas saturation (Sg) maps show that the density map can give sand distribution, but not the gas saturation, as the density is affected by lithology and porosity. On the other hand, the AV F map can show gas saturation distribution, but not the lithology and porosity. Therefore, the density and AV F maps should be combined to get the complete distribution of lithology, porosity and gas saturation.