Abstract
Low-salinity water injection has been utilized as a promising method for oil recovery in recent years. Low-salinity water flooding changes the ion composition or brine salinity for improving oil recovery. Recently, the application of nanoparticles with low-salinity water flooding has shown remarkable results in enhanced oil recovery (EOR). Many studies have been performed on the effect of nanofluids on EOR mechanisms. Their results showed that nanofluids can improve oil recovery when used in low-salinity water flooding. In this work, the effects of injection of low-salinity water and low-salinity nanofluid (prepared by adding SiO2 nanoparticles to low-salinity water) on oil recovery were investigated. At first, the effects of ions were investigated with equal concentrations in low-salinity water flooding. The experimental results showed that the monovalent ions had better performance than the divalent ions because of them having more negative zeta potential and less ionic strength. Also, low-salinity water flooding recovered 6.1% original oil in place (OOIP) more than the high-salinity flooding. Contact angle measurements demonstrated that low-salinity water could reduce the contact angle between oil and water. Then in the second stage, experiments were continued by adding SiO2 nanoparticles to the K+ solution which had the highest oil recovery at the first stage. The experimental results illustrated that the addition of SiO2 nanoparticles up to 0.05 wt% increased oil recovery by about 4% OOIP more than the low-salinity water flooding.
Highlights
Low-salinity water (LSW) flooding has been suggested as an effective method for enhancing oil recovery (EOR) in sandstone reservoirs when the salinity of the injection fluids is between 1400 and 5000 ppm (Alotaibi et al 2010; Austad et al 2010; Buikema et al 2011; Hilner et al 2015; Lager et al 2008b; Morrow and Buckley 2011; Piñerez Torrijos et al 2016; Qiao et al 2016; Vledder et al 2010) and most of the experiments were done below 100 °C, there appeared to be no limitation on temperature (Lager et al 2008a)
The mechanisms suggested in low-salinity water flooding include: double-layer expansion between fine particles and limited fines release (LFR) with a change in wettability toward water wetness resulting from the removal of the mixed wet fines (Tang and Morrow 1999), double-layer expansion between oil/rock contact areas (Ligthelm et al 2009; Matthiesen et al 2014; Nasralla and Nasr-El-Din, 2014; Xie et al 2014), and multi-component ion exchange (MIE) (Lager et al 2007)
Previous studies have reported the effectiveness of low-salinity water flooding on enhanced oil recovery
Summary
Low-salinity water (LSW) flooding has been suggested as an effective method for enhancing oil recovery (EOR) in sandstone reservoirs when the salinity of the injection fluids is between 1400 and 5000 ppm (Alotaibi et al 2010; Austad et al 2010; Buikema et al 2011; Hilner et al 2015; Lager et al 2008b; Morrow and Buckley 2011; Piñerez Torrijos et al 2016; Qiao et al 2016; Vledder et al 2010) and most of the experiments were done below 100 °C, there appeared to be no limitation on temperature (Lager et al 2008a). One of the main mechanisms in nanofluid-assisted flooding is called the structural disjoining pressure (Chengara et al 2004; Wasan et al 2011; Wasan and Nikolov 2003). This mechanism deals with the energy existing between nanoparticles that leads to Brownian motion and electrostatic repulsion between them. The wedge film can separate the formation fluids (oil, water, and gas) from the formation’s surface, thereby recovering more fluids (Mcelfresh et al 2012) Beside this mechanism, the surface modification of porous media in contact with nanoparticles should be considered. The recovery mechanism was discussed using multiple analyses such as IFT, contact angle, zeta potential, and viscosity
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