Wettability of Hybrid Nanofluid-Treated Sandstone/Heavy Oil/Brine Systems: Implications for Enhanced Heavy Oil Recovery Potential

Abstract

In this work, we investigated heavy oil/brine systems on oil-wet sandstone surfaces to quantify the performance of hybrid nanofluids (HNFs) for wettability alteration. In the first step, nanofluid stability analysis was conducted to screen effective single nanoparticles for formulating HNFs and ensure that the properties of the formulated HNFs did not change during the experiments. Then, the ability of HNFs to change the wettability of oil-wet sandstone surfaces to a water-wet state was systematically examined and compared with five types of single nanofluids by contact angle measurements. Then, the effects of HNF composition, hybrid nanoparticle concentration, salinity, and exposure time on the wettability change of sandstones were investigated. Finally, the mechanisms for the wettability shift by HNFs were proposed and verified by scanning electron microscopy visualizations. The results showed that the SiO2 + Al2O3, SiO2 + TiO2, and Al2O3 + TiO2 nanofluids could maintain their stability in the harsh reservoir conditions and that they efficiently induced the wettability change of oil-wet sandstone surfaces to a strongly water-wet state under all operational conditions. The SiO2 + Al2O3 nanofluid achieved the highest wettability alteration efficiency (from 156° to 21° at 0.1 wt % HNF). The efficiency was improved by adding a nonionic surfactant and increasing the hybrid nanoparticle concentration, salinity, and exposure time. However, beyond a certain value, the efficiency slightly decreased due to the instability of the HNFs. Two adsorption kinetics models were applied to predict the measured contact angles at different concentrations and exposure times with good agreement. The stronger adsorption of hybrid nanoparticles on sandstone surfaces was considered to be the underlying mechanism for the higher efficiency of HNFs for the wettability shift than that of single nanofluids.

Phase behavior of heavy oil–solvent mixture systems under reservoir conditions

“…The calculated analysis of variance table for saturation pressures is shown in Table 7, where DF is the degrees of freedom, SS is the sum of the squares, MS is the mean squares, F is a variance-related statistical parameter. A detailed description of the parameters in Table 7 can be found elsewhere (Sun et al 2017b(Sun et al , 2018bZendehboudi et al 2011). As shown in Table 7, the calculated F value is 64,619.31, which is much higher than the critical value of F c (7.71) and provides strong evidence against the null hypothesis.…”

Synergistic Effect of Nanofluids and Surfactants on Heavy Oil Recovery and Oil-Wet Calcite Wettability

“…Therefore, when the salinity was lower than the optimal level, the contact angle decreased due to nanofluid instability. However, when the salinity reached the optimal level, the contact angle increased slightly, due to adsorption of Na + onto the oil-wet calcite surface [ 41 ], and its occupation of adsorption sites further increases nanoparticle adsorption. Therefore, the contact angle would increase further [ 42 ].…”

“…When SiO 2 , MgO, and TiO 2 nanoparticles were combined together, the contact angle of the oil-wet calcite surface decreased to 19.8°. Thus, hybrid nanofluids could effectively alter the oil-wet calcite surface wettability, due to the following reasons [ 41 , 43 ]: Firstly, different species of nanoparticles have different shapes and sizes. Compared to the single nanoparticles, the shape of the hybrid nanofluids became more compact and showed a uniform distribution when different nanoparticles were combined.…”

“…Both nanofluids and surfactants alone could make the oil-wet calcite surface hydrophilic, but the mechanisms were different. When nanofluids alone were used to treat an oil-wet calcite surface, the nanoparticles would adsorb onto the surface [ 41 , 44 ]. The detailed mechanism is shown in Figure 22 .…”

Enhancement of Heavy Oil Recovery with High CO2 Injection Rates in Silica Nanochannel

“…Enhanced oil recovery [1][2][3][4][5][6][7][8][9] is critical for the petroleum industry to recover the residual oil. Among many oil recovery techniques, CO 2 flooding [10][11][12][13][14][15][16][17] is one of the most effective and successful methods to extract the heavy oil from reservoirs.…”