Comparative Study of Using Nanoparticles for Enhanced Oil Recovery: Wettability Alteration of Carbonate Rocks

TLDR

Nanofluids have emerged as promising chemical agents for enhanced oil recovery, with studies demonstrating their ability to alter rock wettability. This study investigates the effects of eight different nanofluids—ZrO₂, CaCO₃, TiO₂, SiO₂, MgO, Al₂O₃, CeO₂, and CNT—on the wettability of carbonate rocks. Nanoparticles were first screened by contact‑angle measurements, then evaluated through spontaneous imbibition, core‑flooding, and drainage capillary‑pressure experiments, with a structural disjoining‑pressure gradient proposed as the underlying mechanism. CaCO₃ and SiO₂ nanoparticles were found to enhance oil recovery by increasing irreducible water saturation and entry capillary pressure, and experiments and theory confirmed that a high disjoining‑pressure gradient at the oil–rock interface can displace oil from the surface.

Abstract

Nanofluids have been recently proposed as new chemical agents for enhanced oil recovery from oil reservoirs. Various nanofluids have been studied in that regard and reported in the literature, verifying the capability of nanostructured materials in enhancing the oil recovery through alteration of rock wettability. In this study, the impacts of different nanofluids of zirconium dioxide (ZrO2), calcium carbonate (CaCO3), titanium dioxide (TiO2), silicon dioxide (SiO2), magnesium oxide (MgO), aluminum oxide (Al2O3), cerium oxide (CeO2), and carbon nanotube (CNT) on the wettability of carbonate rocks were investigated. A series of preliminary contact angle evaluations were performed to screen the nanoparticles. The performances of the selected nanofluids were evaluated by spontaneous imbibition and core flooding experiments. Results of spontaneous imbibition tests and coreflooding experiments confirm the active roles of CaCO3 and SiO2 nanoparticles for enhancing oil recovery. In addition, the effect of nanofluid injection on rock surface wettability was examined by drainage capillary pressure measurement. It is shown that the irreducible water saturation and the entry capillary pressure were both increased after treatment by CaCO3 nanaofluid. Moreover, the structural disjoining pressure gradient is proposed to be the responsible mechanism for changing wettability. Both experiments and theoretical calculations prove that disjoining pressure of the nanoparticles layer near the contact point can be high enough to remove oil from the surface.