Discrepancy in Oil Displacement Mechanisms at the Equivalent Interfacial Tensions: Differentiating Contributions from Surfactant and Nanoparticles on Interfacial Activities

TL;DR

This paper investigates how surfactants and nanoparticles differently influence oil displacement at similar interfacial tensions, revealing distinct mechanisms and efficiencies that challenge common assumptions in enhanced oil recovery.

Contribution

It demonstrates that surfactants and nanofluids exhibit different displacement behaviors and mechanisms at equivalent interfacial tensions, emphasizing the need to reconsider nanoparticle roles in EOR.

Findings

Surfactants outperform nanofluids at high interfacial tension in oil recovery.

Both systems show similar efficiencies at lower interfacial tensions but via different mechanisms.

Nanofluids primarily rely on mechanisms other than interfacial tension reduction.

Abstract

This study examines discrepancies in oil displacement mechanisms at equivalent interfacial tensions, focusing on the distinct contributions of surfactants and nanoparticles. It was hypothesized that similar interfacial activities would result in consistent displacement outcomes, while differences would reflect unique interfacial behaviors. Micromodel experiments revealed that at high interfacial tension (~20 mN/m), surfactants outperformed nanofluids in efficiency and ultimate oil recovery by reinforcing capillary forces. Conversely, nanofluids showed limited ability to modify interfacial forces. At lower interfacial tensions (6.5 mN/m for surfactants, 15.6 mN/m for nanofluids), both systems displayed similar displacement efficiencies and fingering patterns, driven by distinct mechanisms: capillary instability for surfactants and expansive layer flow for nanofluids. These findings challenge the assumption that nanofluids rely primarily on interfacial tension reduction for enhanced oil recovery (EOR) and highlight the need to refine our understanding of nanoparticle interfacial activities. Future studies should extend these insights to core-scale experiments for a more comprehensive evaluation of two-phase flow dynamics.