Impacts Of The Spatial Variation Of Permeability On The Transport Fate Of Dense Non-aqueous Phase Liquids

DNAPLs (dense non-aqueous phase liquids) are denser than water, poisonous, water-insoluble and viscous. Once leak, they will easily pollute soil and groundwater, harm to human health and the environment. To remove them effectively, we should understand their migration law under the ground.The spatial variation of porous media has important impact on the transport fate of dense non-aqueous phase liquids, which controls the velocity and the transport paths of DNAPLs. Permeability is one of the most important factors of porous media, so it is significant to study the impact of its spatial variation on DNAPLs’migration.Firstly, four cases heterogeneous permeability fields with different standard deviations were built using SGSIM (Sequential Gaussian Simulation). Then on the basis of the above fields, multiphase flow models were conducted in saturated and unsaturated porous media respectively with DNAPLs leakage. We used T2VOC, a numerical simulator for multi-components, multi-phases flow underground, to simulate DNAPLs’transportation. At last, according to the saturation of DNAPL at the end of injection time, spatial moment analysis method was used to investigate the impact of permeability’s variation on DNAPL’s migration.The results show that, with the enlargement of the variation of permeability, either in soil or in water:(1) DNAPLs’ first and second order moments decrease in the direction of infiltration, indicating that the mass center is closer to the injection point, and DNAPLs’extent decreases; (2) DNAPL’s moments variance are significantly increased, namely quality, its saturation variation increases; (3) the phenomenon that DNAPL prefers hypertonic channel and aggregates in hypotonic zones is more apparent; (4) DNAPL’ mass in non-NAPL phase is growing gradually. In conclusion, heterogeneous fields complicate the migration of DNAPLs in the fields. The more heterogeneous the media, the smaller range the DNAPL expands, the more irregular the expansions shape. Moreover, the saturation’s fluctuation range and the concentration effect are also increased with the heterogeneity of media.