Application of polymeric nanofluids for enhanced oil recovery in mid-permeability sandstone

Abstract

Enhanced Oil Recovery (EOR) processes are used to recover bypassed and residual oil trapped in a reservoir after primary and secondary recovery methods. Recently, polymeric nanofluid, a novel material formed from the incorporation of polymer and nanoparticle has gained prodigious attention and is proposed for EOR due to its sterling and fascinating properties. Nonetheless, previous studies have focussed more on the suitability of inorganic silica and non-metallic polymeric nanofluids (PNFs). Besides, the performance evaluation of PNFs on pore scale displacement efficiency remains obscure while the mechanistic understanding of this novel material for heavy oil recovery in typical reservoir conditions is elusive in literature. The aim of this study is to explore and exploit the effect of nanoparticles on rheological properties of partially hydrolysed polyacrylamide (HPAM) at varying electrolyte concentration and temperature conditions. Besides, IFT and wettability alteration potential of the PNFs in the presence of heavy oil were evaluated. Herein, two PNFs namely silicon dioxide (SiO2) and aluminium oxide (AhOs), formulated from the combination of the individual nanoparticles and HPAM were exclusively studied. The nanoparticles were characterised using transmission electron microscopy, while the formulated PNFs were characterised using Fourier transform infrared microscopy and thermo gravimetric analysis to determine the morphology and thermal stability respectively. The rheological properties of the PNFs and HPAM were determined using Brookfield RST. Furthermore, the behaviour of the PNFs and HPAM at oil-water interface was investigated using Kruss tensiometer. Moreover, the wettability effect of the fluids in sandstone cores was examined using DataPhysics optical contact angle equipment. Finally, heavy oil displacement in mid-permeability sandstone cores at typical reservoir condition was carried out using HPHT core flooding equipment. Experimental results show that the rheological properties improved while degradation of HPAM molecules was inhibited due to the addition of NPs. At 2,000 ppm HPAM solution (27 mol % hydrolysis degree), 0.1 wt.% NP concentration was found to be the optimal choice for AhO3 and SiO2 NP which gives rise to the highest viscosity on the rheological characterization. PNFs exhibited better steady shear viscosity performance under the different electrolyte concentration and temperature studied due to shielding effects. Besides, PNFs lowers IFT of heavy oil due to irreversible adsorption of the NP’s at the oil-water interface. Moreover, PNF’s alter wettability of sandstone cores from oil-wet to water-wet due to structural disjoining pressure mechanism. Field emission scanning electron microscope and energy-dispersive x-ray analysis confirm adsorption of nanoparticles on the sandstone cores. Finally, heavy oil displacement test in midpermeability sandstone cores showed that incremental oil recoveries of AhO3 and SiO2 PNFs at their optimum concentration were 10.6% and 6.1% respectively over HPAM. Physical filtration phenomena lowered the efficiency of the PNF’s at higher concentrations. The synergic combination of NPs and polymer resulted in enhanced properties of HPAM, hence, culminating in enhanced sweep and pore scale displacement efficiencies. This study is beneficial for extending the frontiers of knowledge in nanotechnology application for EOR.