Abstract
Microfluidics is an appealing method to study processes at rock pore scale such as oil recovery because of the similar size range. It also offers several advantages over the conventional core flooding methodology, for example, easy cleaning and reuse of the same porous network chips or the option to visually track the process. In this study, the effects of injection rate, flood volume, micromodel structure, initial brine saturation, aging, oil type, brine concentration, and composition are systematically investigated. The recovery process is evaluated based on a series of images taken during the experiment. The remaining crude oil saturation reaches a steady state after injection of a few pore volumes of the brine flood. The higher the injection rate, the higher the emulsification and agitation, leading to unstable displacement. Low salinity brine recovered more oil than the high salinity brine. Aging, initial brine saturation, and the presence of divalent ions in the flood led to a decrease in the oil recovery. Most of the tests in this study showed viscous fingering. The analysis of the experimental parameters allowed to develop a reliable and repeatable procedure for microfluidic water flooding. With the method in place, the enhanced oil recovery test developed based on different variables showed an increase of up to 2% of the original oil in place at the tertiary stage.
Highlights
More than half of the original oil in place is left behind in the reservoirs after shutdown.[1,2] At this scale, even slight improvements in extraction would result in an enormous amount of additional recovered oil and value for the society while reducing the environmental impact
Tracking the pressure was useful at the experiment development stage
The typical trend for the pressure is as follows: the pressure increases almost steadily since the syringe pump starts pumping and as the flood goes through the network
Summary
More than half of the original oil in place is left behind in the reservoirs after shutdown.[1,2] At this scale, even slight improvements in extraction would result in an enormous amount of additional recovered oil and value for the society while reducing the environmental impact. Much of the oil remaining in the reservoir prior to this stage is microscopically trapped in the pores by capillary action. The amount of remaining oil depends largely on the ratio between the viscous forces displacing the oil and the capillary forces trapping the oil. The interactions between crude oil, brine, and reservoir rocks are essential for the efficiency of recovery. This means that how much, how fast, and how completely oil can be extracted from a reservoir is primarily governed by phenomena and processes that occur at the pore level, that is, length scales in the micrometer range
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