Modeling contaminant partitioning between residual oil and mobile water phases in porous media: A time variant source of contamination

Residual hydrocarbons residing above or within an aquifer can serve as a continuous time-variant source of contamination to the aquifer. The primary mechanism for contamination is the movement of water past the immobile oil, leaching the partially soluble components from the oil phase into the aqueous phase, and transporting them to or within the aquifer. This research has focused on modeling the transport process. Three models for simulating the dissolution and transport from a residual oil zone are presented and evaluated: a "two-site" model, an "apparent" non-linear partitioning model, and a numerical equilibrium model. The two-site model is shown to be the most descriptive. The apparent partitioning model has been incorporated into a horizontal transport model. The capability and the limitations of the modified horizontal transport model are demonstrated for a hypothetical site. In addition, the effect of decoupling the transport equations for a multicomponent oil is investigated.