Abstract
A selection flowchart that assists, through Computational Fluid Dynamics (CFD) simulations, the design of microfluidic experiments used to distinguish the performance in Chemical Enhanced Oil Recovery (CEOR) of two surfactants with very similar values of interfacial tension (IFT) was proposed and its use demonstrated. The selection flowchart first proposes an experimental design for certain modified variables (X→: porosity, grain shape, the presence of preferential flowing channels, and injection velocity). Experiments are then performed through CFD simulations to obtain a set of response variables (Y→: recovery factor, breakthrough time, the fractal dimension of flow pattern, pressure drop, and entrapment effect). A sensitivity analysis of Y→ regarding the differences in the interfacial tension (IFT) can indicate the CFD experiments that could have more success when distinguishing between two surfactants with similar IFTs (0.037 mN/m and 0.045 mN/m). In the range of modifiable variables evaluated in this study (porosity values of 0.5 and 0.7, circular and irregular grain shape, with and without preferential flowing channel, injection velocities of 10 ft/day and 30 ft/day), the entrapment effect is the response variable that is most affected by changes in IFT. The response of the recovery factor and the breakthrough time was also significant, while the fractal dimension of the flow and the pressure drop had the lowest sensitivity to different IFTs. The experimental conditions that rendered the highest sensitivity to changes in IFT were a low porosity (0.5) and a high injection flow (30 ft/day). The response to the presence of preferential channels and the pore shape was negligible. The approach developed in this research facilitates, through CFD simulations, the study of CEOR processes with microfluidic devices. It reduces the number of experiments and increases the probability of their success.
Highlights
This research proposed and demonstrated a flowchart for selecting microfluidic experiments to evaluate the performance of surfactants in the low interfacial tension range
The flowchart guides the user through comprehensive Computational Fluid Dynamics (CFD) simulations, experimental design, and sensitivity analysis with the ultimate goal of defining the microfluidic characteristics and the experimental conditions that can make the difference between two surfactants either in one specific output variable, e.g., recovery factor, or in a set of performance variables more evident
For the output variables that can be measured in microfluidic experiments and that were considered in the analysis, i.e., recovery factor, breakthrough time, fractal dimension, pressure drop, and entrapment effect, the latter is the one that makes the differences between the surfactants used in the study more evident; the recovery factor and the breakthrough time can be used to distinguish between surfactants
Summary
Surfactant injection has been a widely used technique to increase the recovery factor in hydrocarbon reservoirs This technique has been extensively studied to optimize its application. One problem present in the surfactant injection is the interaction that it may have with a porous medium, causing adsorption of the fluid on the rock and decreasing the effective concentration of surfactant that will act at the interface between the displacing fluid and the crude. Another point of interest in the surfactant application is the change in wettability that it can cause in the medium, favoring the recovery process
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