Rheological characteristics and flow dynamics of polymer nanohybrids in enhancing oil recovery from low permeable carbonate oil reservoirs

As the chemical flooding has proved to be one of the most efficient methods to unlock the trapped oil in porous media, studies on any further improvements in the rheological, phase, and flow behaviors of the common Chemical Enhanced Oil Recovery (CEOR) agents through the use of nanostructured-based materials have gathered significant importance in the field of petroleum engineering. Despite the extensive research in this area, the role of physical properties of polymers including molecular weight (MW) in the improvement of the flow characteristics of the resultant hybrid in a low-permeable carbonate rock has been scrutinized neither experimentally nor numerically so far. The purpose of this study was to clarify the effect of dispersed Hydrophilic Silica-Nanoparticles (HSNPs) in the polymer solution on the improvement of oil recovery during polymer flooding. Thus, rheological studies were performed to scrutinize the impacts of salinity, polymer content, and polymer MW on the viscoelastic behavior of the hybrid. An understanding of how the hybrid behaves when flowing through a relatively low-permeable carbonate rock was acquired by conducting core flood experiments. To monitor the mechanisms of the fluid flow and determine the influencing factors in the fluid distribution through complex pore systems, microfluidic models were utilized. The viscoelastic behavior of the hybrid shows that dispersing HSNPs in a polymer solution consisting of a polymer with lower MW can improve the viscosifying ability and non-Newtonian behavior of the solution. This trend becomes more noticeable by increasing polymer content. However, the employed Nanoparticles (NPs) have a distinct impact on the non-Newtonian behavior of the polymers with higher MW. The results from core flooding experiments reveal that the oil recovery factor is nearly 60% of Original Oil In-Place (OOIP) for the hybrid flooding, which displays pronounced enhancement in ultimate oil recovery, due to the proper mobility ratio of the displacement process. Pore-scale observations and the outputs of numerical simulations exhibit that wettability reversal and polymer adsorption reduction are also responsible for the improvement of oil recovery. The findings of this study not only present the underlying mechanisms of oil recovery during the hybrid flooding of low-permeable carbonate rocks but also provide a new reference for formulating a novel CEOR agent.