Polymeric nanofluids of oilfield polymers for subsurface flow applications: Synthesis, interfacial and rheological analysis

Abstract

This study investigates the potential of stable polymeric nanofluids synthesized via the single-step route for subsurface flow applications in oilfields. The nanofluids were prepared using polymers e.g., polyvinyl alcohol (PVA) (8000 ppm) and xanthan gum (XG) (2000 ppm) and following characterization, their properties were found to exhibit shear thinning profile as well as exhibit great stability at higher salinity. The study focuses on assessing their suitability by surface and interfacial investigations along with conducting shear and oscillatory rheology studies under varying shear conditions. In absence of saline environment, minimum interfacial tension (IFT) value for XG based nanofluid having size 100 nm (X1) was 4.3 mN/m among XG based nanofluids whereas PVA based nanofluid having size 115 nm (P4) exhibited minimum IFT of 7.3 mN/m among PVA based nanofluids. Among prepared nanofluids, P4 and X1 exhibited minimum value of IFT at higher salinity of 32000 ppm, that is, 8.3 mN/m and 6 mN/m and IFT was conducted between crude oil and nanofluid. In addition, during wettability studies, PVA based nanofluid having size 16.9 nm (P2) and X1 possessed minimum value of contact angle, which is 60° and 55° at higher salinity of 32000 ppm. The findings provide valuable insights into the rheological behavior of these nanofluids, shedding light on their performance and potential applications in oilfield environments. All the prepared nanofluids exhibited a shear thinning nature and were in the range of 28.719 mPa.s to 18.128 mPa.s at a shear rate of 1000 s⁻¹. With an increase in temperature (90 °C) causing the nanofluids to exhibit a fall in the values from 68.7 % to 37 %. Finally, the oscillatory rheology was conducted to analyze the viscoelastic properties of all prepared nanofluids and are found to be viscoelastic in nature. The reported observations contribute to advancing the understanding of polymeric nanofluids' behavior in complex flow conditions, laying the groundwork for further research and application development in the field of subsurface flow management.