Synthesis and Oil Displacement Performance of HMPAM-C ₁₈ S/PS-C ₁₈ Nanofluids

In this study, a hydrophobically modified polyacrylamide (HMPAM-C18S) and surface-modified polystyrene nanoparticles (PS–C18) were synthesized using sodium 2-acrylamido-octadecanesulfonate (NaAMC18S) as the hydrophobic monomer and emulsifier, respectively. A polymer-based nanofluid for enhanced oil recovery (EOR) was developed by blending HMPAM-C18S and PS-C18. The effect of the NaAMC18S content on the water solubility of HMPAM-C18S as well as the particle size and emulsion stability of PS-C18 were investigated. The properties of HMPAM-C18S and HMPAM-C18S/PS-C18 nanofluid solutions were compared. Experimental results demonstrated that PS-C18-1.0 enhanced the molecular network structure of HMPAM-C18S through van der Waals interactions, significantly improving its apparent viscosity, thermal resistance, salt tolerance, and shear stability. Under reservoir conditions (65 °C, 6070 mg/L salinity, and core permeability of 1200 mD), the HMPAM-C18S/PS-C18-1.0 nanofluid (1500 mg/L HMPAM-C18S + 1000 mg/L PS-C18) exhibited a higher resistance factor (RF) and residual resistance factor (RRF) compared to HMPAM-C18S. The EOR reached 28.95%, which was 8.95% higher than that achieved by HMPAM-C18S.