SIGNIFICANCE OF POROSITY VARIABILITY TO TRANSPORT IN HETEROGENEOUS POROUS-MEDIA

We use Monte Carlo simulations of flow and transport in two-dimensiona l random conductivity, porosity, and geochemistry fields to explore th e influence of their spatial variability on flow and transport process es for both conservative and reactive chemicals. For conservative tran sport, results show that when the porosity is correlated to the hydrau lic conductivity (which may be expected in geologic formations); the d ispersion process is significantly affected. Positive cross correlatio n between the porosity and the conductivity decreases dispersion, whil e a negative correlation tends to increase dispersion in the longitudi nal direction. For reactive transport in physically and chemically het erogeneous media, the geochemical variability alone yields results tha t are significantly different than when both geochemistry and porosity are random space variables correlated to the conductivity field. Thes e results suggest that it is necessary to examine the role porosity va riability and its correlation to the conductivity play in transport th eories. The stochastic perturbation transport theory, previously devel oped by our group for conservative chemicals, is modified to account f or the porosity variability and its correlation with the hydraulic con ductivity. The results of the modified theory support the Monte Carlo simulations and indicate that porosity variability significantly affec ts the second longitudinal moment. The implication of the study for fi eld problems depends on the existence of cross correlation between por osity and conductivity.