Understanding Fluid-Fluid and Fluid-Rock Interactions in the Presence of Hydrophilic Nanoparticles at Various Conditions
Authors: Hendraningrat Luky , Torsæter O. 
Published: September 2014

Abstract
Examining fluid behavior in the presence of nanoparticles is essential to understand the displacement mechanism when a nanoparticle is used as novel enhanced oil recovery (EOR) method. Recent investigations showed that nanoparticles have great potential for EOR in the lab-scale. Since its displacement mechanism is not yet clearly understood, studies about fluid-fluid and fluid-rock interactions will be essential as a way to unlock how its mechanism.
Saline water is studied in the presence of hydrophilic silica nanoparticles at different conditions such as temperature, concentration, various salt ions and nanoparticle size and initial rock wettability. The fluid properties measurement involves density, viscosity, pH and surface conductivity. Crude oil from a field in the North Sea is employed to measure interfacial tension between oil-phase and aqueous phase (saline water and nanofluids) at different temperatures. Contact angle is also measured among quartz rock as solid phase and those fluid phases at different initial rock wettability.
These compatibility tests is useful to have better understanding about displacement mechanism and boundary of using nanoparticles as EOR method (Nano EOR) before applying in the field-scale. The processes and observations are outlined and also further detailed in the paper as a part to unlock nanoparticles flooding as a future promising EOR method.
Introduction
Nanofluid is a new class of fluid engineered and a new interdisciplinary area of great importance where nanoscience, nanotechnology, and thermal engineering come across (Yu and Xie, 2011). It is defined as nanoparticle that has average size less than 100 nm, suspended in traditional heat transfer fluid such as water, oil or ethylene glycol (Das et al., 2008). Nanofluid consists of two-phase systems, solid and liquid (Yu and Xie, 2011) since nanoparticles (NPs), as solid phase, is commonly dispersed in liquid. Nanofluids have greatly attracted in wide range fields application in recent years. Yu and Xie (2011) highlighted the current application of nanofluids such as heat and mass transfer enhancement (Kim et al., 2006, 2007a, and 2007b; Ma et al., 2007, and 2009), friction reduction and magnetic sealing in mechanical application (Kim et al., 1999; Shen et al., 2008; Yu et al., 2008; Mitamura et al., 2008; Chen and Mao, 2010; Peng et al., 2010; and Vekas et al., 2010), and biomedical application (Zhang et al., 2007; Jalal et al., 2010; Jones et al., 2008; Liu et al., 2009; Mahapatra et al., 2008; Nakano, 2008; Singh and Liliard, 2009; and Gajjar et al., 2009).
The potential of nanofluids for oil and gas industries application has been summarized by Kong and Ohadi (2010), as presented in Table 1. It can be also used for geochemical exploration (Wang et al., 1997). Another benefit of nanofluids in drilling and sand problem has been investigated by Chaaudhury (2003), Zitha (2005), and Evdokimov et al. (2006). In heavy oil application, it can upgrade the viscosity of heavy oil and bitumen as a catalyst (Ying and Sun, 1997; Scott et al., 2003; and Hendraningrat et al., 2014a).
The NPs easily aggregated once they hydrated. It is because they have a large surface-to-volume ratio due to the small particle size. For instance, Fig. 1 shows hydrated silica when dispersed in base fluid such as water (has hydrogen element). The materials with high surface-to-volume ratios react at much faster rates because additional surfaces are available to react. Therefore they possess high surface energies. The NPs consequently create an aggregate form to minimize this surface energy.