Experimental Measurement of Dynamic Effect in Capillary Pressure Relationship for Two-Phase Flow in Weakly Layered Porous Media

Well-defined laboratory experiments have been conducted to determine the significance of dynamic effect in capillary pressure relationships for two-phase flow in weakly heterogeneous (layered) porous media. The heterogeneous layers are composed of a fine sand layer sandwiched between two coarse sand layers. Dynamic and quasi-static capillary pressure-saturation (P-c-S) and partial derivative S/partial derivative t-t relationships are determined, which are then used to determine the dynamic effect, indicated by a dynamic coefficient (tau). As well known, tau establishes the speed at which flow equilibrium (partial derivative S/partial derivative t = 0) is reached. In consistent with previous studies, tau is found to be a nonlinear function of saturation that depends on the medium permeability and the intensity of heterogeneity. tau values increase in the regions of less permeability (fine sand) in the domain. However, the tau-S functional dependence follows similar trends at different locations within the domain including regions of different permeability. We argue that saturation weighted average of local tau-S curves can be used as an effective tau-S curve for the whole domain which, when done, follows an exponential trend too. The effective tau-S curves suggest that the effective tau values for the porous layers lie between the tau values of coarse and fine sands at the same water saturation, and it is dominated by the tau values of coarse sand as it occupied the maximum volume of the domain. (C) 2012 American Institute of Chemical Engineers AIChE J, 59: 1723-1734, 2013