Enhanced oil recovery by spontaneous imbibition of imidazolium based ionic liquids on the carbonate reservoir

• Published in: Journal of molecular liquids 2021-10, Vol.340, p.117301, Article 117301
• Main Authors: Sakthivel, Sivabalan, Elsayed, Mahmoud
• Format: Article
• Language: English
• ISSN: 0167-7322; 1873-3166
• DOI: 10.1016/j.molliq.2021.117301

•Spontaneous imbibition with ILs resulted in 27–34% of additional recovery.•ILs altered the rock wettability favorably and thus improved the oil recovery.•ILs work efficiently even in harsh environments at dilute concentrations.•Longer chain ILs showed better efficacy on the wettability alteration.•NMR study confirms the ILs effect in all types of pores, unlike SW. Wettability alteration plays an important role in the enhanced oil recovery (EOR), particularly for the oil-wet carbonate reservoir in harsh environments. It is essential to alter the native oil-wet characteristics of the rock matrix into water-wet or intermediate-wet in an attempt to achieve the favorable EOR process. The rate of water imbibition can be greatly improved by altering the rock wettability and by reducing oil–water interfacial tension. This can be achieved by using smart water, surfactants, oilfield chemicals, functionalized nanoparticles, or a combination of these to enhance water imbibition and oil displacement. In this study, a suite of spontaneous imbibition tests was run and investigated the efficacy of eco-friendly imidazolium-based ionic liquids (ILs) on the oil-wet carbonate sample and evaluated their effectiveness for the enhanced oil recovery with the minimal concentration of ILs (≤500 ppm). In this, we have studied the various affecting parameters including; type of ILs, ILs concentration (0–500 ppm), aging time (0–8 weeks), and rock permeability (45 and 250 mD). Subsequently, two conventionally used surfactants (SDS and CTAB) were also screened for the same study in order to set the reference case. All these experiments were performed on the Indiana limestone core samples, and experimental condition was set as high temperature (100 °C) and high brine salinity (TDS: 240, 000 ppm) in order to represent the typical Saudi Arabian reservoir condition. Overall, it was observed that a maximum of 34% increment of oil recovery was recorded for IL case over the seawater. Whereas only 11% of increased recovery was achieved with the use of conventional surfactants than the seawater. It is also noted that the longer chain containing ILs had shown better recovery (34%) than the shorter chain containing ILs (27%). Furthermore, NMR T2 relaxation distribution and NMR T2D responses were acquired for the same study. This helps to estimate the rate of water invasion and oil recovery both qualitatively and quantitatively. NMR measurements confirm that seawater was ineffective in all the por