SIMULATION OF IMMISCIBLE MULTIPHASE FLOW IN POROUS-MEDIA - A FOCUS ONTHE CAPILLARY-FRINGE OF OIL-CONTAMINATED AQUIFERS

This paper deals with the analysis of some aspects of the vertical and lateral migration of oil spills in the unsaturated and the capillary zone of a phreatic aquifer. Our motivation stems from the fact that su ch contamination represents a severe danger for ground-water resources all over the world and from the present acute problem of jet-fuel con tamination in some location of Israel. In the present study, we shall focus our efforts on the analysis of the upper layers of the aquifer w hich are often subjected to the most significant oil contamination. Ne glecting coupled processes effects such as dilution, adsorption and vo latilization, also adopting Richard's assumption, a three-phase flow m odel is introduced with capillary heads of the water and the oil as va riables. The resulting model which is coupled and strongly non-linear is solved using a vertical two-dimensional Finite-Element procedure to gether with a quasi-Newton optimization algorithm. Applying that schem e, various scenarios of oil migration in the unsaturated and the capil lary zone were simulated. Some migration characteristics prediced by t he numerical simulations are discussed. In particular, the dynamics of the water and oil phases during the migration process is discussed.