Carbon dioxide enhanced
oil recovery (CO2-EOR) has been
widely used to improve production from mature oil fields around the
world. To be effective, the injected gas and reservoir oil must develop
miscibility, which generally requires prolonged contact between the
two phases while in relative motion. Thus, identifying whether miscibility
is possible is crucial for determining the feasibility of such EOR
projects. The current industry-standard method of characterization,
the slim-tube, requires weeks of analysis, while alternative methods
are unable to infer all routes to miscibility, producing significant
overestimates in required pressures. Microfluidic devices have the
potential to simplify and speed up the analysis by offering high levels
of fluid control and excellent visualization. Recently, high-pressure
microfluidic devices etched into glass and exploiting crude oil’s
natural fluorescence have been successfully demonstrated. Here we
focus on designing a microfluidic channel for identifying the development
of miscibility. We prove its accuracy for a known ternary fluid system
that mimics the true oil–gas system and can be manipulated
at room temperature and pressure. Our chip consists of a single channel
with several inline pocket structures. The chip is initially flooded
with one phase before a second phase is injected via a flow-rate-controlled
pump. The first phase is then rapidly displaced in the primary channel,
but small samples are retained within the pockets. Over time, these
trapped droplets can be observed as they interact with the continuously
flowing second phase. When the fluid concentrations meet the conditions
for development of miscibility, a dramatic and visually observable
change in behavior occurs, allowing for characterization within 2
h.