Abstract
Water-soluble polymers are known to be used in chemically enhanced oil recovery (EOR) processes, but their applications are limited in high-temperature and high-salinity oil reservoirs because of their inherent poor salt tolerance and weak thermal stability. Hydrophobic association of partially hydrolyzed polyacryamide (HAHPAM) complexed with silica nanoparticles to prepare nano-hybrids is reported in this work. The rheological and enhanced oil recovery (EOR) properties of such hybrids were studied in comparison with HAHPAM under simulated high-temperature and high-salinity oil reservoir conditions (T: 85 °C; total dissolved solids: 32,868 mg∙L−1; [Ca2+] + [Mg2+]: 873 mg∙L−1). It was found that the apparent viscosity and elastic modulus of HAHPAM solutions increased with addition of silica nanoparticles, and HAHPAM/silica hybrids exhibit better shear resistance and long-term thermal stability than HAHPAM in synthetic brine. Moreover, core flooding tests show that HAHPAM/silica hybrid has a higher oil recovery factor than HAHPAM solution.
Highlights
Among various enhanced oil recovery (EOR) methods, polymer flooding (PF) has been considered an attractive alternative to conventional water flooding because of its high potential for recovering more oil from reservoirs [1,2,3]
Intermolecular hydrophobic associations may play against the interaction between Hydrophobic association of partially hydrolyzed polyacryamide (HAHPAM) and silica nanoparticles, rheological behaviors of HAHPAM/silica hybrids were studied at a fixed polymer concentration of 0.5 wt% (
With addition of silica nanoparticles, G′ of the hybrids is higher than that of HAHPAM solution, indicating the nanoparticles increasingly influence the elastic properties of the polymers. These results suggest that HAHPAM/silica hybrids undergo microstructural changes and they have the ability to increase the oil recovery factor in high-temperature and high-salinity oil reservoirs because of the increased elastic modulus
Summary
Among various enhanced oil recovery (EOR) methods, polymer flooding (PF) has been considered an attractive alternative to conventional water flooding because of its high potential for recovering more oil from reservoirs [1,2,3]. The interaction of metal ions such as Na + and K+ in the oilfield brines largely shields the mutual repulsion from the carboxylic groups along the HPAM skeleton, leading to the polymer coils to collapse and the hydrodynamic volume to decrease, lowering the solution viscosity [12,13] Another major limitation of HPAM is its flow-induced mechanical degradation because of its shear-thinning behavior. The strong interactions between PNIPAM and silica are generally attributed to the formation of hydrogen bonds between the amide groups of NIPAM and silanol functionalities on the nanoparticle surface Based on these preliminary results, it is concluded that silica nanoparticles can effectively interact with water-soluble polymers which have carbonyl groups and act as physical crosslinkers between macromolecules, reinforcing the polymer structures and improving the mechanical properties of the polymers. HAHPAM was tested under the same experimental conditions
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