Development and incorporation of a NAPL residual into the Lenhard-Parker pressure-saturation hysteretic model

The current three-phase hysteretic Lenhard-Parker (LP) pressure-saturation model does not allow for estimates of residual non-aqueous phase liquid (NAPL) saturation terms within multiphase systems. Residual NAPL saturation may be present in significant amounts within the subsurface and may control remediation techniques to be used on NAPL contaminated sites. Thus, some method to include residual NAPL saturation within the current LP model is required. A number of pressure-saturation experiments were conducted in the laboratory to determine two-phase pressure-saturation parameters required by the LP model, and the factors influencing residual NAPL saturation in three-phase systems.;The three fluids considered were water, heptane, and air, and the porous medium chosen was a well sorted gray silica sand. From the experimental results, three conceptual model equations were developed to estimate residual NAPL saturation within three-phase systems. The conceptual model results were then incorporated into a LP hysteretic pressure-saturation code, and a simple example problem presented.;The importance of including a NAPL residual saturation within the LP model was clearly illustrated by the example problem given. Future work should consider different three-phase fluid/porous medium systems, and verification of the conceptual models presented by comparing simulated data to laboratory/field data.