Seismic Reservoir Characterization of Wara Formation by Prestack Simultaneous Inversion Using Low Frequency Model with Faults

Abstract The prestack simultaneous inversion was carried out to predict the lithologies in Wara Formation in SE Kuwait. The Wara formation is highly faulted in the study area, so it is very necessary to run inversion using a proper earth model including all faults. Three lithologies (sand, shaly sand and shale) were identified on well logs using Vsh cutoffs. This provides the foundation for log crossplot and PDF analysis for seismic lithology prediction. Seismic angle stacks were amplitude-balanced, and aligned properly before the inversion process began. Inversion parameters were optimized, and the inversion results were quality checked by comparing the inverted impedance and Vp/Vs to well logs at well locations, and the match was good. Wara geological mapping was carried out by using inverted impedance, Vp/Vs and sand frequency volumes. Prospect areas were highlighted for the future development drilling consideration. All these locations are structurally high, with low mean Vp/Vs values and high sand probabilities. In addition, the comparison between inversion results using faults and without using faults was made in this study. A significant effort was made to make sure the inversion results are due solely to differences in the low frequency model (LFM), namely the presence or absence of faults in the LFM. Through the quantitative comparison, it was found that more precise sand prediction was made near faults by using the LFM with faults. Overall, this case study highlights the importance of including faults in LFM for seismic lithology prediction and reservoir property prediction near faults by using prestack seismic inversion.