Optimizing Nanoparticle-Polymer Formulations for Enhanced Oil Recovery in High-Salinity, High-Temperature Reservoirs

Abstract The objective of this work is to develop a nanoparticle-polymer formulation for EOR applications in high-salinity, high-temperature reservoirs. Conventional polymer solutions, such as hydrolyzed polyacrylamide (HPAM), usually degrade under extreme conditions due to reduced viscosity and poor stability, hence limiting their applications in EOR. This work discusses the possibility of improving stability, viscosity, and resistance to salinity of HPAM-based polymer solutions with the use of different nanoparticles: multi-walled carbon nanotubes (CNT), zinc oxide (ZnO) nanoparticles, colloidal silica, and powder silica. The research is designed to find the most effective nanoparticle-polymer combinations that can enhance oil recovery efficiency in challenging reservoir environments, with a focus on achieving long-term stability and performance under harsh conditions. These studies were conducted for the synthesis and characterization of different nanoparticle-polymer mixes by advanced techniques of Fourier-transform infrared spectroscopy (FT-IR), and rheology tests. The stability and viscosity of all the prepared formulations were studied in high-salinity conditions of up to 50,000 ppm NaCl and at elevated temperatures up to 80°C. Accordingly, all kinds of nanoparticles were evaluated according to their capabilities with regard to the stability of polymers under harsh conditions. In addition, the influence of nanoparticle concentration from 0.1% to 1.0% wt. on the performance of the polymer solution was systematically investigated. Silica-based nanoparticles, colloidal, and powder silica showed superior performances and significantly enhanced the stability and viscosity of HPAM polymer solutions under high- salinity and high-temperature reservoir conditions. For example, colloidal silica increased the viscosity of the polymer solution by more than 40%. Under the same conditions, the viscosity of powder silica increased by 35%. On the contrary, CNT and ZnO exhibited poor stability and retention of viscosity by showing a 20-30% decrease in their properties under extreme conditions. These findings point out the better role of silica-based nanoparticles in enhancing polymer stability and oil recovery efficiency in extreme reservoir conditions. This paper's novelty lies on optimization of nanoparticle-polymer formulations developed for EOR applications under high-salinity, high-temperature reservoir conditions. The utilization of colloidal and powder silica as stabilizing agents for HPAM polymers constitutes an important step forward in EOR technology, presenting a cost-effective and efficient solution against such a challenge. Research provided great insight into the synergy between nanoparticles with polymer stability and viscosity, representing an opportunity to explore other nanomaterials of higher functionality for use in EOR. These also presented possibilities of upscaling the formulation for field application, thereby increasing the domain of application for nanotechnology within the oil and gas industry.