Nanofluid of Petroleum Sulfonate Nanocapsules for Enhanced Oil Recovery in High-Temperature and High-Salinity Reservoirs

Petroleum sulfonate (PS) salt surfactants that are insoluble in high-salinity water were encapsulated into 10-60 nm oil swollen micelles dispersed by a cocamidopropyl hydroxysultaine zwitterionic cosurfactant to form a highly stable nanofluid at elevated salinity (similar to 56 000 mg/L) and temperature (similar to 100 degrees C). The resulting "Nano-Surfactant (NS)" fluid enables an economic, efficient, and environmentally friendly enhanced oil recovery (EOR) capable of targeted delivery of PS salt surfactants-one of the most abundant and inexpensive industrial surfactants, yet cannot be used in most EOR operations because of its insolubility in high-salinity water-to residual oil without the need of massive amounts of surfactants. The NS formulations presented here can be easily prepared in the field by a simple one-pot, one-step procedure at ambient temperatures and with a minimal energy input. This article reports the preparation method of the NS and results, demonstrating their long-term colloidal and chemical stability at 100 degrees C, reduction of crude oil-high-salinity water interfacial tension (IFT) by 3 orders of magnitude (from similar to 10 to 0.008 mN/m), and improved mobilization of the trapped crude oil from the carbonate rock. Results point out the potential of NS formulations in enhancing oil mobilization under a variety of reservoir conditions. The NS platform described here can be utilized to encapsulate and deliver a variety of other chemical treatments, not only in oil recovery applications but also in others such as remediation of nonaqueous phase liquid-contaminated groundwater aquifers, well-drilling operations, and wellbore stimulation.