(17b) Immiscible Displacement in Homogeneous and Heterogeneous Porous Media: Quantifying Interfacial Phenomena

Immiscible displacement is ubiquitous in many subsurface multiphase flow systems and pore-scale characterization of these processes aids in the development of quantitative, empirical relationships required in Darcy-scale models. Here, we present experiments in which a wetting fluid is displaced by a non-wetting fluid in homogeneous and heterogeneous porous micromodels. The resulting steady-state fluid distributions are analyzed to characterize fluid-fluid and fluid-solid interfacial length in terms of saturation, fingering pattern, capillary number, and porosity. A comparison between the homogeneous and heterogeneous experiments demonstrates that heterogeneity expands the range of conditions under which capillary fingering is observed. In all micromodels, the number of non-wetting isolated fingers (i.e., blobs and ganglia) increased within the range of injection flow rates. The results show a clear relationship between interfacial length and saturation; however we did not observe a clear relationship between interfacial length and fingering pattern. In addition, once saturation was taken into account, interfacial length was independent of the capillary number. A clear relationship is observed between the non-wetting–wetting fluid interfacial length, non-wetting fluid saturation, and porosity. We anticipate our results will serve as model to quantify relationships for interfacial phenomena in pore-scale drainage and help with the development of Darcy-scale models.