Improvement of ensemble smoother with SVD-assisted sampling scheme

By using randomly chosen 100 ensembles, it shows overshooting problem and provides poor future performances. For the conventional sampling scheme of adopting the largest singular values, it has a potential of biased results as the reference field is complex and heterogeneous. However, our proposed method using 100 ensembles represents as large spectrum as using all 400 ensembles. It also reduces overshooting problem and improves the quality of future reservoir performances. Through ES with the improved sampling scheme, it ensures efficient and reliable reservoir characterization for history matching.