Ensemble smoother with clustered covariance for 3D channelized reservoirs with geological uncertainty

However, ESC manages overshooting problem in ES and preserves bimodal distribution with reliable uncertainty ranges in reservoir performances. It requires about 4% of history matching time of EnKF for the cases tested. Furthermore, only 10 reservoir models selected from the distance-based clustering can replace 200 total ensembles for uncertainty quantification. Therefore, ESC can be applicable to 3D channelized reservoirs with geological uncertainties.