Reservoir characterization of gas saturated sandstone using Extended Elastic Impedance (EEI), Poisson Impedance (PI) and Curved Pseudo Elastic Impedance (CPEI)

The WR field in this study is a gas hydrocarbon proven field with high saturation rate and reservoir character in tight sandstone. There are prestack 3D seismic data and three well data that have P-wave velocity (Vp) and S-wave velocity (Vs). In its development there are three kind of methods using Vp, Vs, and angle function constants that is Extended Elastic Impedance (EEI), Poisson Impedance (PI), and Curved Pseudo Elastic Impedance (CPEI). By using correlation coefficient concept between two kinds of variable, we can look for the angle function constants which used in those three methods. The results obtained from those three methods correlated with lithology log data (Gamma ray (GR)) at the range of angle (-90° to 90°) is EEI = 30°, PI = 59° and CPEI = -69°, whereas with fluid log target (Water Saturation (SW)) obtained angle values correlated with EEI = 20°, PI = 51° and CPEI = -60°. The highest correlation to the target lithology (GR) and fluid (SW) log data of the three methods is CPEI with correlation 0.881 for lithology and 0.604 for fluid. The vertical of the three methods shows a good reservoir character with high saturation rate of gas. The result of the lateral distribution of the three methods shows the character of the depositional environment in the target reservoir located in the estuarine environment in upper shoreface facies for Reservoir A and transition facies for Reservoir B. The direction trend of the source of the sedimentary sediment is the south-east direction, and this result fits with the regional geological concept in the WR field.