Reservoir Characterization using Simultaneous Inversion for Identifying the Sandstone Reservoir of Air Benakat Formation "IDY" Field in South Sumatra Basin

This research was conducted using simultaneous inversion seismic method. The inversion method can be used not only to identify reservoirs, but to identify the fluid content in a rock formation. Formation in this study is Air Benakat Formation, in the South Sumatra Basin. Simultaneous inversion has the results in the form of P-impedance, S-impedance, density, P-wave velocity, S-wave velocity, and upsilon(p)/upsilon(s). From the data that have been obtained, that IDY-1 well is considered as a gas saturated sandstone reservoir. Fluid Replacement Modeling (FRM) was also used, in this study, to obtain the detailed information about the presence of gas in the Air Benakat Formation. FRM can simulate the state of the formation if it were in an in situ case condition, and in the gas case condition. From the results of FRM processing, that is for the gas case condition of 90%, it was obtained the upsilon(p)/upsilon(s) value of 1.75 to 1.875. While, in the in situ case condition, the ratio was obtained to be 2.0 to 2.2. Based on simultaneous inversion results, the research area is known to have a P-impedance value of 5800 to 6000 (m / s) * (g / cc), an S-impedance of 2000 to 4000 (m / s) * (g /cc), the density of 2.2 to 2.27 g/g/cm(3), and the upsilon(p)/upsilon(s) ratio of 2.17 to 2.25. To identify the distribution of sandstone reservoirs, a horizontal cross-section map was made, which produced results of the cross section of low impedance and low upsilon(p)/upsilon(s) value. This shows that the IDY-1 well is a well-saturated sandstone reservoir.