Publications

Pre-stack simultaneous inversion is a part of quantitative interpretation as a reservoir characterization tool to identify lithology and pore fluid based on P-wave velocity, S-wave velocity, and density. The Gumai Formation facies architecture is complex and formed by interbedded sand and – shale. The formation has various roles in the Jambi Sub-Basin petroleum system acting as the regional seal, source rock, and reservoir rock. This research was carried out in order to discriminate lithology and detecting pore fluid distribution using Pre-stack Simultaneous Inversion in the Gumai Formation, Jambi subbasin which is supported by the proven discoveries of hydrocarbon (gas) while Drill Stem Testing (DST). The data consists of 3D seismic partial angle stacks and well log data which are used as input to three-term Fatti equation to transform the seismic trace into reflectivity. Further, reflectivity from different angle stacks are simultaneously inverted to obtain P-impedance (Zp), S-Impedance (Zs) and Density (ρ). The simultaneous inversion results for gas bearing sand reservoir encased in shale gave low P-Impedance value (15,700-18,250 ft/s*gr/cc or 4,785-5,563 m/s*gr/cc), low S-Impedance value (9,078-10,850 ft/s*gr/cc or 2,767-3,307 m/s*gr/cc) and low density value (2.10-2.19 gr/cc). Based on these values, combined maps of P-impedance (Zp), S-Impedance (Zs) and Density (ρ) show the distribution of the prospective areas for gas bearing sand reservoir towards western part of the study area.