Two-phase flow experimental studies in micro-models

Abstract

The aim of this research project was to put more physics into theories of two-phase flow. The significance of including interfacial area as a separate variable in two-phase flow and transport models was investigated. In order to investigate experimentally the significance of the inclusion of interfacial area as a separate variable in two-phase flow studies, an artificial porous medium was designed and constructed. First, an extensive and comprehensive review of micro-models materials and manufacturing processes, visualization setups used, and their applications in two-phase flow studies was performed. Based on this review, the manufacturing material for our micro-model studies was chosen. In addition to this, the lack of an optical setup that can visualize flow in elongated micro-models was discussed. In order to calculate quantities like pressure drops, flow rates, relative permeabilities per phase, so as to better design the experimental setup, a pore network model was made. A flow network based on Delaunay triangulation was used to simulate drainage and imbibition under quasi-static conditions. Calculations for capillary pressure, wetting phase saturation, and interfacial area were used to construct the relevant surfaces, for various configurations of the flow network. Intrinsic permeability of the flow network, as well as relative permeability for both phases, were calculated for drainage. Typical flow rates were also calculated, so as to be later compared to experimental values. A micro-model made of silicon and sealed with a glass plate was then manufactured, and it was used to study oil recovery in natural rocks. A novel, all-glass micro-model was used to compare the experimental results to those obtained by the numerical model, under quasi-static conditions, during drainage. A novel optical setup which would allow the dynamic observation of pore scale flow processes in an elongated micro-model was designed and materialized for this purpose. Next, a PDMS micro-model was manufactured by using soft-lithography, to be used in quasi-static and dynamic two-phase flow experiments. A novel process was employed to make PDMS uniformly and stably hydrophobic, so as to resolve the well-known wettability issues of PDMS. Quasi-static and dynamic experimental data for capillary pressure, wetting phase saturation, and specific interfacial area, during drainage, imbibition, and their scanning curves, were extracted from the acquired images. These data were used to test the validity of the new capillarity equation for two-phase flow, by comparing the surfaces plotted for Pc-S-Awn, and verifying that interfacial area should be used as a separate variable in two-phase flow models. Finally, some experimental observations, like snap-off, local imbibition during drainage and vice versa, co-operational filling, and capillary end-effects, which are assumed in numerical models but not seen in experiments were captured for further studies.