Complex lithological reservoir prediction through pre-stack simultaneous inversion: a case study from the Leijia Area in Liaohe Oil-field, China

Abstract

Summary The study area named Leijia area of the Liaohe Oil-field is located in the NorthEastern of China. The lithology of the reservoir at S4 member of Paleogene is characterized by argillaceous carbonate and breccia, and the lower volume of the shale, the better oil bearing ability of the reservoir. Reservoir characterization using post stack inversion method to estimate P-impedance alone was not able to differentiate the reservoir (argillaceous carbonate and breccia) and non reservoir (dolomitic shale and limy shale) lithologies in these formation. This is due to the low contrast in P-impedance among the argillaceous carbonate, dolomitic shale, limy shale, sandstone and breccia. An attempt at reservoir prediction was made by using shear impedance derived from pre-stack simultaneous inversion along with P-impedance to discriminate reservoir lithologies and non-reservoir lithologies. The DEMGassmann rock physics model (Wang et al., 2011; Sun et al., 2012) is employed to calculate the shear logging data which is used in the process of the pre-stack simultaneous inversion and rock physics analysis. The result of rock physics analysis shows that reservoir and non- reservoir lithologies can be differentiated by the combination of Pimpedance, S-impedance, and Vp/Vs elastic properties. Consequently, the result of lithological prediction is in good accordance with drilling wells and the coincidence rate reached 100%. Furthermore, these results would be an extremely useful guidance for further exploration and development in the Leijia Area.