The characterization and visualization of multi-phase systems using microfluidic devices
Conn, Charles Andrew
Biswal, Sibani L
Doctor of Philosophy
The stability and dynamics of multi-phase systems are still not fully understood, especially in systems of confinement such as microchannel networks and porous media. In particular, systems of liquids and gases that form foam are important in a number of applications including enhanced oil recovery (EOR). This research seeks to better understand the mechanisms of multi-phase fluid interaction responsible for the displacement of oil. The answers to these questions give insight into the design of efficient EOR recovery strategies, and provides a platform on which researchers can perform studies on pore-level phenomena. Our experiments use poly(dimethylsiloxane) (PDMS) devices which can be made using inexpensive materials without hazardous chemicals and can be designed and fabricated in just a few hours to save time, money, and effort. The unique contribution of this thesis is the development of a general “reservoir-on-a-chip” research platform that facilitates study of multi-phase systems relevant to energy-industry applications. Experiments with a fractured porous media micromodel quantified pressure drop and remaining oil saturation for different recovery strategies. It demonstrated foam flooding’s superior performance compared to waterflooding, gas flooding, and water-alternating-gas flooding by increasing flow resistance in the fracture and high-permeability zones and directing fluids into the low-permeability zone. Mechanisms of phase-separation were observed which suggest it is inappropriate to treat foam as a homogeneous phase. Experiments with foam in a 2-D porous matrix investigated mechanisms of foam generation, destruction, and transport and related foam texture (bubble size) to pressure drop and apparent viscosity. MATLAB code written for this thesis automated quantification of over 120,000 bubbles to generate plots of bubble size distributions for alpha olefin sulfonate (AOS 14-16) at different foam quality (gas fraction) conditions. The experimental devices and analytical software tools developed in this work open the door for future experiments to screen and compare surfactant formulations. One may readily envision developing libraries of surfactant data from micromodel experiments which can then be data-mined to discover relationships between surfactant structure, performance, and environmental conditions.