Mass- and temperature-dependent diffusion coefficients for lightnoble gases for the TOUGH2-EOSN Model

This report describes modifications made to the EOSN module(Shan and Pruess, 2003) of the nonisothermal multiphase flow simulatorTOUGH2 (Pruess, et al., 1999). The EOSN fluid property module simulatestransport of water, brine, air, and noble gases or CO2 in the subsurface.In the standard version of the EOSN module, diffusion coefficients can bespecified by the user, but there is no allowance for liquid-phasediffusion coefficients to change with temperature. Furthermore, usersmust specify radiogenic sources of heat and helium for each element indata block GENER, which can be a time-consuming task for models withlarge numbers of elements. Our modifications seek to increase thefunctionality and efficiency of using TOUGH2-EOSN by allowing for mass-and temperature-dependent liquid-phase diffusion coefficients for heliumand neon and specification of radiogenic heat and helium production as aproperty of a material. The modified version is based on TOUGH2-EOSN andthus requires familiarity with the capabilities and input formats of theTOUGH2 code (Pruess, et al., 1999) and the EOSN module (Shan and Pruess,2003). This report only details our modifications and how to properlyutilize them