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PARAMETER ESTIMATION OF TWO-FLUID CAPILLARY PRESSURE-SATURATION AND PERMEABILITY FUNCTIONS
Citation:
Hopmans, J. W., M. E. Grismer, J. Chen, AND Y. P. Liu. PARAMETER ESTIMATION OF TWO-FLUID CAPILLARY PRESSURE-SATURATION AND PERMEABILITY FUNCTIONS. U.S. Environmental Protection Agency, Washington, D.C., EPA/600/R-98/046 (NTIS 98-151236), 1998.
Impact/Purpose:
publish information
Description:
Capillary pressure and permeability functions are crucial to the quantitative description of subsurface flow and transport. Earlier work has demonstrated the feasibility of using the inverse parameter estimation approach in determining these functions if both capillary pressure and cumulative drainage are measured during a transient flow experiment. However, to date this method has been applied to air-water systems only, while ignoring the air phase, thereby assuming that the air phase has a negligible influence on water flow. In this study, we expanded the inverse parameter estimation method combined with multi-step outflow data, using a modified Tempe cell for air-water, oil (Soltrol)-water, and air-oil fluid pairs in a Columbia fine sandy loam and a Lincoln sand. The commonly applied van Genuchten (VG)-Mualem (M) model of capillary pressure and permeability functions was used in this study. Wetting-fluid and oil non-wetting fluid pressures were measured in the center of a soil sample simultaneously with cumulative outflow of the wetting fluid as the initially near-saturated soil core is drained by increasing the non-wetting fluid pressure in a sequence of pressure increments. Results from the multi-step measurements are used to directly estimate capillary pressure and wetting fluid permeability functions. Uniqueness and stability analysis indicated that the inverse model is well posed, and that the multi-step transient outflow experiment provides sufficient information to successfully apply the parameter estimation approach.