Discrete wellbore simulations of pump-and-treat strategies for remediation of LNAPL-contaminated aquifers

The method for simulating wells screened over several computational nodes described in Wu et al. [Wu, Y., Forsyth, P., Jiang, H. (1996). A consistent approach for applying numerical boundary conditions for multiphase subsurface flow. J. Cont. Hyd., 23:157–184.] is applied to multiphase LNAPL remediation problems. Computational issues concerning modelling wellbore flow are discussed. Three-dimensional computations are presented using a multiphase, nonequilibrium mass transfer model, which show the effect of well placement and geometry on containment of the dissolved LNAPL plume and the dissolution of the NAPL phase. It is also shown that unless very small aqueous phase dispersion parameters are used, classical dispersion theory can produce unrealistic dispersion against the flow direction in the neighbourhood of a pumping well. Except in the long term, this may have implications regarding the prediction of near-field plume configuration and contaminant capture.