Fly Ash Nanoparticle-Stabilized Emulsions for Improve Mobility Control Application

Abstract

Nanoparticles have demonstrated their capacity to increase emulsion stability by forming what is known as a Pickering emulsion, which is predicted to improve EOR processes by improving conformity control. The goal of this work is to develop a novel way of beneficially utilizing the main waste product from coal power-generation plants - fly ash - by generating fly ash nanoparticle-stabilized emulsions for improved mobility control, especially under high-salinity conditions. First, the ball-milling method was used to decrease the grain size of fly ash, which was too big for injection into reservoirs. Second, fly ash nanoparticles were used to measure the synergy between nanoparticles and surfactants in the creation of oil-in-brine emulsions. Third, the emulsion stability was tested using a microscope and a rheometer with three different surfactants (cationic, nonionic, and anionic). Finally, oil replacement experiments were conducted using intra-formation heterogeneous cores to investigate the recovery enhancement effect of in situ injection of fly ash nanoparticles and cationic surfactant (CS). Thermally treated fly ash (TTFA) nanoparticles with an average size of 150 nm were produced using nano-milling and thermal treatment techniques. The use of either a cationic or nonionic surfactant in conjunction with nanoparticles resulted in strong and stable emulsions. The cationic surfactant had the greatest synergy, while the anionic surfactant had the least, indicating that electrostatic interactions with the surfactant and the liquid/liquid interface were key factors. The in-situ emulsion formed by the fly ash nanoparticles and the cationic surfactant (FA-CS) produced an additional 8.5 % of the original oil in place (OOIP) recovery after waterflooding. This indicates that the emulsion has better mobility control performance and higher crude oil recovery. This study not only has the potential to minimize the amount of surfactant used for emulsion-based EOR mobility control of fly ash nanoparticles but also to sequester fly ash in the subsurface strata.