Modeling for the separation of light nonaqueous phase liquids from contaminated subsurface through vacuum-enhanced oil recovery

摘要

Vacuum-enhanced recovery (VER) technique has been widely used for separation and removal of light non-aqueous phase liquids (LNAPLs) at petroleum-contaminated sites. In order to effectively design a VER process, a mathematical simulator is desired for simulating multiphase flows of LNAPLs, water and air in subsurface. In this study, a model for simulating the separation of LNAPLs from contaminated soil and groundwater through the VER system at a petroleum contaminated site is proposed. The constitutive interrelationships among the three phase flows are addressed through development of governing and constitutive equations of the movement of immiscible LNAPLs flow in a three-phase system. The proposed method invokes an assumption of near-equilibrium conditions in the vertical direction. This could reduce the nonlinearity in the constitutive model and transforms a 3D problem into a 2D areal problem, thereby, drastically reducing computational time for the simulation. The proposed model is then applied to a case study in western Canada where the soil and groundwater are contaminated by leakage of hydrocarbons from underground storage tanks. Through the simulation process, reasonable results have been obtained. They indicate that the proposed method is effective in simulating the separation and recovery process of LNAPLs from contaminated subsurfaces. Useful bases for VER system design and site remediation actions can be provided through this study.