Characterization of hydrocarbon reservoir at field “B”, South Sumatera by using poisson impedance inversion

Abstract

The separation process of lithology and fluid reservoir is an important part in the characterization of reservoir. It will explain the physical properties of reservoir rock lithology and fluid content by integrating the geophysics and petrophysical data. This process is difficult to do in the field "B" by using parameters of acoustic impedance and lambda mu rho (LMR), because it still has a fairly high degree of ambiguity. Poisson impedance (PI) has been implemented as a solution to address the problem. In cross-plot between Acoustic Impedance (AI) and Shear Impedance (SI), a rotation of both axes was conducted according to the trend of lithology-fluid to satisfy the equation of PI = AI – cSI. To improve the accuracy of PI calculation, the value of c (optimization factor of rotation) was calculated through the method of TCCA (Target Correlation Coefficient Analysis). The correlation with to be predicted wells data then be done. Analysis of sensitivity parameter was performed on two wells in the field "B". Parameters Zp, Zs and density which obtained from the simultaneous inversion then transformed into PI.  PI models clearly showed the separation of rock lithology of hydrocarbon reservoir. Lithology impedance (LI) as a result of the PI-GR correlation was able to separate sand and shale very well. Similarly, the impedance Fluid (FI) as a result of PI-SW correlation was also able to separate the water content in the reservoir with high SW value relative to gas with a low value of SW. Hydrocarbon zone proven at 2360-2400 m. The slicing result of the volumes of Poisson impedance inversion has provided a clear distribution and interpretation of lithology and fluid content reservoir at the field "B" of South Sumatera.