Kun Ma

Visualization of improved sweep with foam in heterogeneous porous media using microfluidics

We demonstrate the use of foam to divert flow from high permeable to low permeable regions in a PDMS heterogeneous porous microfluidic system. Foam is generated using a flow-focusing microfluidic device with co-flowing gas and aqueous surfactant streams. Foam quality (gas fraction) is modulated by adjusting the flow rate of the aqueous surfactant solution while keeping the gas inlet pressure fixed. The foam is then injected into an aqueous-solution filled heterogeneous porous media containing a high and low permeable region and sweep of the saturated aqueous phase is monitored. Compared with 100% gas injection, surfactant-stabilized foam is shown to effectively improve the sweep of the aqueous fluid in both high and low permeable regions of the porous micromodel. The best performance of foam on fluid diversion is observed in the lamella-separated foam regime, where the presence of foam can enhance gas saturation in the low permeable region up to 45.1% at the time of gas breakthrough. The presented results are useful in understanding and designing foam injection in porous underground formations for aquifer remediation and enhanced oil recovery processes.

Adsorption of cationic and anionic surfactants on natural and synthetic carbonate materials.

Adsorption of cationic and anionic surfactants on carbonate materials is investigated in this study. Cetylpyridinium chloride (CPC) and sodium dodecyl sulfate (SDS) are chosen as typical cationic and anionic surfactants, respectively. It is found that the cationic CPC exhibits negligible adsorption on synthetic calcite in deionized water compared with the adsorption of the anionic SDS. However, a substantial amount of adsorption of CPC is observed on natural carbonates, such as dolomite and limestone. X-ray photoelectron spectroscopy (XPS) reveals that that a substantial amount of silicon and aluminum exists in natural dolomite and limestone but not in synthetic calcite. The adsorption plateau of CPC on carbonates highly depends on the silicon composition in the carbonate samples due to the strong electrostatic interaction between CPC and negative binding sites in silica and/or clay. The adsorption of CPC on natural carbonates is reduced in the presence of 1atm CO2 compared with the case under 1atm air, while SDS precipitates out of the solution under 1atm CO2 due to its intolerance to divalent ions released from the carbonate surface as a result of CO2 acidification.

Switchable Nonionic to Cationic Ethoxylated Amine Surfactants for CO2 Enhanced Oil Recovery in High-Temperature, High-Salinity Carbonate Reservoirs

Yunshen Chen, SPE, Amro S. Elhag, and Benjamin M. Poon, Department of Chemical Engineering, University of Texas at Austin; Leyu Cui, and Kun Ma, Department of Chemical and Biomolecular Engineering, Rice University; Sonia Y. Liao, Prathima P. Reddy and Andrew J. Worthen, SPE, Department of Chemical Engineering, University of Texas at Austin; George J. Hirasaki, SPE, Department of Chemical and Biomolecular Engineering, Rice University; Quoc P. Nguyen, SPE, Department of Petroleum and Geosystems Engineering, University of Texas at Austin; Sibani L. Biswal, Department of Chemical and Biomolecular Engineering, Rice University; and Keith P. Johnston, Department of Chemical Engineering, University of Texas at Austin

Neighbor-induced bubble pinch-off: novel mechanisms of in situ foam generation in microfluidic channels

We utilize a microfluidic constriction to demonstrate two new mechanisms of in situ foam generation in porous media. The initial foam was generated using a flow-focusing geometry with co-flowing gas and surfactant solution streams and then flowed through a microfluidic constriction. By varying the gas and surfactant solution flow rates, different types of monodisperse foams were generated in which two bubbles (2-bubble foam), three bubbles (3-bubble foam), or more than three bubbles (>3-bubble foam) spanned the channel width. It was expected that the bubbles would snap off upon passing through the constriction; however, in our system, the snap-off mechanism was observed only under unstable conditions, namely, when the foam was wet and had a large bubble size. Instead, the following behaviors were observed as stable foam passed through the constriction: no change, reorientation, and pinch-off, which included two newly observed mechanisms (neighbor–wall pinch-off and neighbor–neighbor pinch-off). Neighbor–wall pinch-off occurs as a bubble is pinched between the surfaces of a neighboring bubble and the curved wall of the constriction. Neighbor–neighbor pinch-off occurs as a bubble is pinched off between two adjacent neighboring bubbles. The width of the pinched bubble as a function of time before pinch-off was found to scale as a power law with exponents of 0.523 ± 0.06 and 1.004 ± 0.05 for neighbor–wall and neighbor–neighbor pinch-off, respectively.

Effect of Surfactant Partitioning Between Gaseous Phase and Aqueous Phase on \hbox {CO}_{2} Foam Transport for Enhanced Oil Recovery

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Estimation of Parameters for the Simulation of Foam Flow through Porous Media: Part 3; Non-Uniqueness, Numerical Artifact and Sensitivity

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Visualizing oil displacement with foam in a microfluidic device with permeability contrast

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