Abstract
In the current study, the effect of CuO nanoparticles (CuO-NPs) at the presence of dodecyl-3-methylimidazolium chloride ([C12mim][Cl]) is investigated on the interfacial tension (IFT) reduction, wettability alteration, and even tertiary oil recovery. Since the prepared solutions with CuO-NPs are completely dark and it is impossible to measure the IFT of these solutions in the presence of crude oil using the pendant drop method (since one of the phases must be transparent for IFT measurement using the pendant drop method), n-heptane (representative of saturates) and toluene (representative of aromatics) are used only for IFT measurement of solutions prepared by CuO-NPs, while rest of the experiments are performed using crude oil. The obtained results reveal that CuO-NPs are not stable in the aqueous solution in the absence of surfactant which means fast precipitation of CuO-NPs and a high risk of pore plugging. In this way, the stability of CuO-NPs is investigated at the presence of dodecyl-3-methyl imidazolium chloride ([C12mim][Cl]) as an effective surfactant for stabilizing the CuO-NPs in the aqueous solution (more than 1 month without precipitation using 1000 ppm of IL). Further measurements reveal that although the presence of IL in the aqueous solution can reduce the IFT of oil/aqueous solution system, especially for the aqueous solutions prepared by formation brine (0.65 mN.m−1), the presence of CuO-NPs has no considerable effect on the IFT. On the other hand, not only the contact angle (CA) measurements reveal the considerable effect of IL on the wettability alteration toward water-wet condition (68.3° for IL concentration of 1000 ppm) but also the addition of CuO-NPs can significantly boost the wettability alteration toward strongly water-wet condition (23.4° for the concentration of 1000 ppm of CuO-NPs). Finally, several core flooding experiments are performed using different combinations of chemicals to find the effect of these chemicals on the tertiary oil recovery factor. The results reveal that the presence of CuO-NPs can enhance the oil recovery of injected chemical slug (aqueous solution prepared by dissolution of IL with an oil recovery factor of 10.1% based on Original oil in place (OOIP)) to 13.8, %, 16.9%, and 21.2% based on OOIP if 500, 1000, 2000 ppm of CuO-NPs existed in the solution concomitant with 1000 ppm of [C12mim][Cl].
Highlights
The majority of the running oil fields around the world are reaching to decline production phase regardless of efforts oil companies performed even using Enhanced oil recovery (EOR) methods such as low-salinity, chemical or water injection (Cheraghian, 2015)
The results revealed that the addition of CuO nanoparticles (CuO-NPs) has a direct increasing effect on the tertiary oil recovery from 13.8 to 21.2% based on original oil in palace (OOIP) which can be considered as the effect of CuO-NPs on the wettability alteration
Increasing the ionic liquid (IL) concentration from 0 to 4000 ppm leads to interfacial tension (IFT) reduction from 27.3 to 0.65 mN.m−1, the sharp reduction in IFT was observed for IL concentration of 250 ppm which can be considered as the critical micelle concentration (CMC) value of this system
Summary
The majority of the running oil fields around the world are reaching to decline production phase regardless of efforts oil companies performed even using Enhanced oil recovery (EOR) methods such as low-salinity, chemical or water injection (Cheraghian, 2015). It seems that individual application of ILs for IFT reduction is not satisfactory for oil recovery purposes (Rodríguez-Palmeiro et al, 2015) In this way, the current investigation is aimed to use the [C12mim][Cl] as IL-based surfactants concomitant with CuO-NPs to modify the wettability of the rock surface and reduce the IFT value to some extent for higher oil recovery. The current investigation is aimed to use the [C12mim][Cl] as IL-based surfactants concomitant with CuO-NPs to modify the wettability of the rock surface and reduce the IFT value to some extent for higher oil recovery In this way, the pendant drop method was used to measure the IFT and measure the contact angle values at different concentrations of IL and CuO-NPs to find the optimum formulation. The optimum formulation was used to perform several core flooding experiments to find the potential of chemical formulation of tertiary oil recovery
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