Abstract
A new class of surfactants for enhanced oil recovery (EOR) applications has been developed in the form of petroleum sulfonate salt nanoparticle dispersions in seawater. These NanoSuractants (NS) are 10- to 60-nm particles of the seawater-insoluble petroleum sulfonate salts, one of the most abundant and inexpensive industrial surfactants, that are resiliently stable in seawater at elevated temperatures via a special class of co-surfactants. They can be easily prepared in the field by mixing with seawater at ambient temperature and injected into the reservoir with seawater without any additional infrastructure. The colloidal nature and extremely small size of the NanoSurfactans particles allow them to migrate and deliver petroleum sulfonates to remaining and residual oil deep in the reservoir without the need of large quantities in order to compensate for losses by adsorption onto the rock surfaces and diffusion into water-filled small pores. This paper reports on the results of few tests conducted to evaluate the performance of NanoSurfactant formulations under reservoir conditions. Results showed consistent colloidal and chemical stability of the NanoSurfactant formulations for over six months at 100°C. They reduced the seawater-crude oil interfacial tension (IFT) by two to three orders of magnitude or formed oil-in-water emulsions at 100 °C without any mechanical mixing. Transmission electron miscroscopy (TEM) images revealed mostly round particle in the submicron range (10- to 60-nm). Finally, core-flood test at reservoir conditions using bottom-hole live oil samples indicated an additional oil recovery of about 7% of OOIP beyond several pore-volumes flooding with seawater by injecting 0.4 pore-volume of the NanoSurfactant at 0.2 wt% concentration.
