Quantitative reservoir characterization through simultaneous inversion: a case study from the Burgan field, Kuwait

Summary The study area is in the Burgan field located onshore in the South-East of Kuwait. Hundreds of wells have been drilled in this field proving the presence of oil in the Wara and Burgan Formations in the Middle Cretaceous interval. It was expected that mapping of the reservoir sands in these formations could be improved by utilizing the spatial coverage of the 3D seismic data. Reservoir characterization using post stack deterministic inversion method to estimate acoustic impedance (P-impedance) alone was not able to differentiate the reservoir and non-reservoir lithologies in these formations. This was due to the low contrast in Pimpedance between sands and shales. An attempt at reservoir characterization was made by using shear impedance (S-impedance) along with P-impedance to discriminate shale and sand properties. Consequently, the simultaneous inversion method was used to derive these rock properties from the 3D seismic data integrated with well log data. The results from simultaneous inversion show that the reservoir and non-reservoir lithologies can be differentiated using the combination of P-impedance and Vp/Vs elastic properties. The combined P-impedance and Vp/Vs results can be utilized to even further predict the fluid in the reservoir. The hydrocarbon bearing reservoir zones in the Wara and Burgan Formations were characterized by a response of low P-impedance and low Vp/Vs and were able to be mapped for future planning of the wells.