Estimation of Parigi reservoir characteristics using seismic attributes, AVO analysis and AVO inversion, and seismic inversion

In the carbonate reservoir, the gas was trapped in the cavity of the formation. First of all, to identify the cavity as the distribution of the cavity or porous zone will be done by reflection strength and instantaneous frequency from the seismic attribute analysis. After the zone has been identified, the existing gas and the value of porosity can be estimated using AVO analysis and AVO inversion technique. This idea was applied to the carbonate reservoir within the Parigi Formation in the Northwest Java Basin (Indonesia) by Santoso et al.(1995). The result shows a clear zone of high reflection strength and low instantaneous frequency in the carbonate build up, The porosity estimated by AVO inversion gives a value of the porosity about 38% and the Poisson's ratio arround 0.22 - 0.26. This paper is continuation of Santoso et al. (1995) study. It is done by the delineation of the porosity which can be displayed by the acoustic impedance section as a result of seismic inversion process. The delineation of the reservoir characters to the horizontal direction as previous study gives arround a similar value as shown by acoustic impedance value. When these results were compared to the borehole data in the location, the are very close. Therefore this idea has given a satisfactory result in estimating porosity from seismic data and delineating the carbonate reservoir away from the borehole.