Effect of Porosity Variability on Ganglia Entrapment during Immiscible Displacement

Ganglia are occluded blobs of non-aqueous phase liquids (NAFL) that arise during the displacement of two immiscible fluids in porous media. Their presence increases the residual saturation of organic fluids during the removal of contaminants. Immiscible flow has several uncertainties that govern the macroscopic behavior of fluids inside porous media. These uncertainties are essentially related to the porous media properties including anisotropy and spatial variability of pore size. The displacement of two immiscible fluids within soil pores is analyzed by means of a micromechanical pore network model. The model assumes that Young-Laplace’s equation governs the interface instability (capillarity prevails over gravity and viscosity). The effect of porosity anisotropy, presence of preferential flow paths, and coefficient of variation of pore size is analyzed. Results show that pattern of ganglia and residual saturation of NAPL are directly related to porosity anisotropy and pore size spatial variability.