PROCEEDINGS, INDONESIAN PETROLEUM ASSOCIATION Thirty-Seventh Annual Convention & Exhibition, May 2013 A SEISMIC ROCK PROPERTIES STUDY OF A MESOZOIC RESERVOIR IN INDONESIA

AVO (amplitude versus offset) is a seismic manipulation applied in the reflectivity domain that can be used to analyze hydrocarbon and lithologic anomalies. Additional analyses are frequently required. For example, Extended Elastic Impedance (EEI) has been found to be an effective discriminator in terms of lithology and fluid separation. Another useful concept is fluid substitution in rock physics modeling to analyze the response to different fluid types. In this study, we performed rock physics modeling on three wells, then determined the optimum projection for separating lithology (sand-shale), and fluids (brine-gas) in a Mesozoic reservoir. Gradient Impedance (EEI 90 o ) gave the optimum projection for lithology separation, while the optimum projection for fluid separation occured in EEI 20 o . Destructive wavelet interference between the top Mesozoic reservoir and top seal on seismic data affected the AVO responses hence a top reservoir response could be achieved only from highfrequency synthetic angle gathers. These responses indicate an AVO change from Class II to Class III as gas saturation increases. The 'Coloured Inversion' method was applied to the data to transform seismic reflectivity to Acoustic Impedance (AI).