Development and characterization of nanostructured surfactant compositions with prolonged action and stimuli-responsible physicochemical properties

Encapsulation of surfactants is a novel and innovative approach that allows the protection of active substances and the control of their prolonged release. The incorporation of surfactant molecules into nanosized capsules will influence intermolecular and electrostatic interactions between surfactants and reservoir rocks, thereby impacting the adsorption and wetting properties of surfaces. Therefore, this work evaluates the performance of novel formulations of encapsulated anionic and cationic surfactants into hollow silica nanoparticles designed for a carbonate oil field. A systematic study was conducted to examine a release rate of surfactants at elevated temperatures (up to 343 K) and various salinities (ranging from 0 to 5 wt% NaCl). The size and morphology were assessed through zeta -potential measurements and microscopy techniques. UV-VIS spectroscopy and contact angle measurements were employed to study the adsorption isotherms of the encapsulated surfactants and their influence on the wetting properties of carbonate surfaces, respectively. This study revealed that encapsulation of surfactants resulted in their prolonged action, and the duration of the capsules' effectiveness depended on temperature and salinity. Adsorption of encapsulated surfactants was found to be less than 1 mg/g of rock, and equilibrium isotherms exhibited Freundlich -type adsorption. The wetting properties of calcite changed from 120 degrees to 30 degrees over 14 days due to the sustained release of surfactant molecules. This marks the first report of the application of encapsulated surfactants for enhanced oil recovery (EOR), enabling the prolonged penetration of surfactants deeper into the reservoir.