Surfactant Modified Cellulose Nanofibrils for Enhanced Oil Recovery

摘要

Trygve Jakobsen, Sebastien Simon, Kristin Syverud, Kristofer Paso. a Norwegian University of Science and Technology, N-7491, Trondheim, Norway; b Paper and Fibre Research Institute, Høgskoleringen 6B, N-7491, Trondheim, Norway; Nanocelluloses have shown promising results as rheology modifiers in water dispersions and as emulsion stabilizers. As non-toxic biomaterials, they show good potential as additives in enhanced oil recovery (EOR). It is desirable to induce enhanced oil recovery on different scales simultaneously. In this case, cellulose nanofibrils (CNF) has the purpose of increasing viscosity in injection water, thereby increasing macroscopic sweep efficiency within the reservoir. Surfactants decrease interfacial tension (IFT) between water and oil, which increases the microscopic sweep efficiency. Both effects will increase the capillary number, diminishing the dominance of capillary force over viscous force, and should result in additional oil recovered. Other factors to consider are loss of surfactant to the rock surface by adsorption, injectivity of CNF into porous rock, changing the wetting state of rock surface, stability towards aggregation of CNF in high salt content, biodegradability and temperature stability. This experimental study is using CNF produced by TEMPO-mediated oxidation, and alkyl sulfonate surfactants in combination with salt. The alkyl sulfonates in question have been proven by others to be very efficient for IFT decrease, and are commercially available. Adsorption of surfactant onto cellulose nanofibrils is compared to change in rheological properties of bulk and interface. Changes in CNF stability towards aggregation in salt has been studied in the presence of surfactant, as it is paramount to ensure injectivity of fibrils.