Effect of SiO 2 nanoparticles + 1-dodecyl-3-methyl imidazolium chloride on the IFT and wettability alteration at the presence of asphaltenic-synthetic oil

Using nanoparticles (NPs) in different industries such as enhanced oil recovery processes increased during the past decade due to its significant effects on the wettability alteration and IFT reduction to some extent. On the other side, ionic liquids (ILs) are proposed a new class of solvents that introduce considerable advantages in different areas of sciences. In this way, a hybrid method based on the NPs and ILs is proposed in the current investigation. So, silicon dioxide (SiO 2) as one of the most effective NPs on the wettability alteration and 1-dodecyl-3-methyl imidazolium chloride ([C 12 mim][Cl]) as a new class of surfactants are used to find their effects on the interfacial tension (IFT) reduction and wettability alteration at the presence of asphaltenic synthetic oil for the first time. In this way, the stability of SiO 2 -NPs at the presence of and absence of IL is examined which revealed stability of SiO 2 -NPs for more than one month at the presence of IL while fast precipitation was observed if no IL existed in the solution. After that, the effect of IL and SiO 2 -NPs on the IFT reduction and wettability alteration is investigated by changing the concentration of these chemicals between 0 and 2000 ppm and ranging the asphaltene content between 2 and 10%wt. The results revealed that for all of the examined concentrations of IL and asphaltene fraction, reduction in IFT is inevitable as the concentration increases. Besides, the results demonstrate that there is a threshold value for asphaltene content (6%wt) in which for the values below or higher than this threshold, the effect of IL on the IFT reduction reduces leading to the vanishing of a sharp reduction in IFT and determining a distinguished critical micelle concentration (CMC). According to findings, for asphaltenic synthetic oil (ASO) with 6%wt asphaltene content CMC value of 250 ppm is obvious while for the other ASO, no obvious and distinguished CMC values exist. Moreover, the results reveal that the IFT reduces to the value of 0.48 mN/m as the IL concentration increases to 2000 ppm while the asphaltene content is kept constant at 6%wt. Further IFT measurements demonstrate the negligible effect of SiO 2 -NPs on the IFT reduction while the concomitant existence of SiO 2 -NPs and IL with the concentration of 1000 ppm moves the wettability of the rock surface toward strongly water-wet with contact angle (CA) of 33.1°. The worth mentioning point is that the entire amount of reduction in the CA from 156.3° (initial condition) to 33.1° at the presence of hybrid solution is not completely due to the presence of SiO 2 -NPs and it is the cumulative effect of IL and SiO 2 -NPs presence. Finally, several core flooding experiments are performed using different chemical formulations which reveal that using a hybrid solution of SiO 2 -NPs + IL with a concentration of 1000 ppm for each chemical increases the tertiary oil recovery to 15.2%wt based on OOIP for the ASO/formation brine with asphaltene content of 10%wt.