Ensemble Kalman Filter (EnKF) Used to Estimate the Multiphase Model Parameters for DNAPL Infiltration Experiments in Heterogeneous Porous Media
Abstract:A series of 2-D sandbox experiments were conducted to investigate the infiltration behavior of dense non-aqueous phase liquids (DNAPL) in saturated heterogeneous porous media. The modified light transmission (LT) method based on Bob et al. (2008) was used to quantify the DNAPL saturation during the infiltration process. A multiphase numerical simulator T2VOC was then used to simulate the experiments. With the EnKF method, static parameters such as permeability, porosity, residual NAPL saturation, and van Genutchen parameters (such as αnw and n), and dynamic variables like DNAPL saturation were continuously updated to match with the realtime observation data from LT method for history matching purposes. It is shown that the EnKF sometimes fails badly in the analysis (or updating) of saturations due to the nonlinearity between model variables and observable variables. Common sequential data assimilation algorithms based on the Kalman filter were also compared and discussed about the multiphase flow problem in porous media.
This research was financially supported by the National Nature Science Foundation of China grants No. 41030746 and 41172206.
 Bob, M.M., Brooks, M.C., Mravik, S.C., Wood, A.L., 2008. A modified light transmission visualization method for DNAPL saturation measurements in 2-D models. Adv. Water Resour., 31, 727-742.