Use of Aromatic Ionic Liquids in the Reduction of Surface Phenomena of Crude Oil–Water System and their Synergism with Brine

Green solution for oil spills: A review on the role of surface-active ionic liquids

Oil spills have long-lasting and harmful impacts on the environment, particularly on aquatic ecosystems. This review provides a comprehensive overview of conventional methods for oil spill removal, highlighting both their advantages and limitations. Traditional methods for addressing oil spills, including physical, thermal, biological and chemical techniques, often prove insufficient, with chemical dispersants being the most popular approach. However, the concern about the toxicity and low biodegradability of these dispersants have led researchers to explore more effective and ecologically benign alternatives. Recently, surface-active ionic liquids (SAILs) have gained interest due to their amphiphilic nature, green and biodegradable characteristics, and excellent performance under various temperature and salinity conditions. In this review, the molecular composition of SAILs, with a specific emphasis on the roles of their head groups, alkyl chains, and counter anions, has been discussed. Additionally, the aggregation behavior of SAILs, their ability to reduce interfacial tension (IFT), and their potential to form stable emulsions, which are important for effective oil dispersion, has been also discussed in the paper. This review also examines key environmental factors such as temperature and salinity that influence the efficacy of oil dispersion using SAILs. The study investigates the possibilities of SAILs as an environmentally friendly substitute for conventional dispersants, while also discussing the challenges and possible future paths for the industry. However, the long-term environmental effects of SAILs and their degradation products are still uncertain, underscoring the necessity of future research. Insights into the optimization of SAIL formulations, their environmental impact, and the feasibility of large-scale application are also discussed, offering a forward-looking perspective on the development of next-generation oil spill remediation technologies.

Application of α-MnO2 nanoparticles for residual oil mobilization through surfactant polymer flooding

Injection of surfactant and polymer slug is among the most effective chemical enhanced oil recovery processes. The only problem encountered with the surfactant polymer (SP) flooding is the loss of surface-active agents that reduce the efficiency of surfactants in the chemical slug. Various attempts to modify SP flooding have been made previously so that the surfactant loss due to adsorption could be reduced. Nanoparticles (NPs) are one of the most effective ways of reducing surfactant adsorption as surfactant particles are held in the liquid phase by nanoparticles, resulting in lower surfactant losses due to adsorption. However, the high cost of the NPs limits their use on the field scale. To encounter this problem, the present study focuses on the application of the manganese dioxide NPs, synthesized through a green route that is economically viable. These NPs are found to be cost-effective as compared to commercially available NPs as well as the synthesis of these NPs does not require the use of toxic chemicals. The 1000 ppm NPs effectively reduced the surfactant adsorption by 46%. The surface tension was lowered from 29.4 to 26.1 mN/m when 1000 ppm NPs were applied to 2500 ppm surfactant solution. Also, the nanoparticles were found to increase the viscosity of the chemical slug by increasing the solid particles present in the slug. The sand pack flooding experiments were carried out to assess the crude oil mobilization ability of the NPs assisted SP flooding. The oil recovery was found to increase from 5% of the original oil in place, resulting in ~ 75% of the crude oil recovery, which was only ~ 70% when NPs were not introduced into the system.

Wettability Alteration of Carbonate Reservoirs Using Imidazolium-Based Ionic Liquids

The wettability of the rock-oil-brine system plays a major role in enhanced oil recovery (EOR), particularly in the harsh environments of carbonate reservoirs. Most of these formations were identified as strongly oil-wet, and sometimes a few are intermediate-wet. Hence, it is highly necessary to alter such an oil-wet rock matrix to a water-wet matrix in order to improve the oil production. Consequently, it is important to investigate the wetting and wettability dynamics of the rock-oil-brine system for both static and dynamic cases. Thus, in this study, we investigated the effect of four various imidazolium-based ionic liquids (ILs) on the wettability alteration of the rock-oil-brine system by measuring the contact angles. Herein, we have screened various parameters, such as the rock type (brine-saturated and oil-saturated), type of IL, IL concentrations (0-1000 ppm), temperature (25-100 °C), pressure (14.7-3000 psi), and salinity (TDS: 67,500-240,000 ppm). The measurement of the static contact angle was found to be altered from 85.5 to 49.4° with the addition of 500 ppm of ILs in the brine-saturated sample, and for the oil-saturated sample, it was altered from 150.9 to 99.2°. This indicates that ILs have a huge influence on shifting the rock wettability more toward water-wet, which in fact is more favorable for the EOR operation. Later, we studied the dynamic wettability alteration of the rock-oil-brine system, in which we measured the transient changes in the contact angle while displacing the brine with an IL solution in situ. It was observed that the oil droplet deformed slightly and was dragged toward the base fluid (IL solution) with time, and this implied the changes in the contact angle from 150.9 to 118.5° with 500 ppm of IL, [C₁₂mim]⁺[Cl]^-. Though this has a relatively lesser impact as compared to the static experiment, this could be considered to be more realistic to correlate with coreflood experiments. Further, to understand the mechanism of this wettability dynamics, we have measured the oil-water interfacial tension and the ζ-potential of various systems and observed that their results were backed up by our wettability studies. Overall, the combined forces of interfacial tension reduction, capillary alterations, and IL interactions with rocks and oils have caused this wettability alteration. Conclusively, the results of various experiments that are performed in this study are more meaningful, and it is evident that ILs favor the successful EOR implications.

Imidazolium based ionic liquid stabilized foams for conformance control: bulk and porous scale investigation

Foams are typically used as a divergent fluid for conformance control in order to divert the fluid flow from a high-permeable zone into a low-permeable zone. Nevertheless, the stability of the foam still remains a challenge due to the presence of antifoaming crude oil and the harsh environment of the reservoir, such as high-temperature, high-salinity, and high-pressure. In this study, we investigated the stability and efficacy of various surfactant generated foams with ionic liquid (IL) additives. Intrinsically, the study is targeted to represent the conditions of Arab-D reservoir formations, which are abundant in Saudi Arabian oilfields. In this, we have screened several parameters that influence foam stability like the type of foamer gases (CO₂, N₂, and air), type of ILs, type of surfactants (nonionic, anionic, cationic, and zwitterionic), concentration, salinity (formation brine, low salinity brine, and seawater brine), temperature, etc. The stability of the generated foams was analyzed in both bulk and porous scale media. The bulk foam study has demonstrated that only a very minor concentration of ILs (50-500 ppm) shows a greater improvement in both the foamability and foam stability. The stability of the foam in the presence of the studied ILs and surfactants increases by more than 50% compared to their neat surfactant solution. A similar response was also witnessed in the dynamic foaming experiments at high-temperature, high-pressure, and high-salinity. The current work also involves the determination of the foam morphology, including structure, size, shape, gas-water interface and the lamellae size for different systems with and without ILs, which helps to understand the stability mechanism of the foams with and without ILs. Confocal and optical microscopic images of the foam structure of various systems reveal that these ILs are successful in reducing the size of bubbles and increasing the lamellae size. It is very clear that the addition of ILs generates the surfactant layered-ILs, and they tend to arrange themselves in the lamellae, and at the liquid-gas interface, thereby decreasing the rate of film drainage at the lamellae and delaying the bubble rupture point. This led to the observed enhanced foam stability. Thus, we would like to conclude that the ILs investigated here improved the foam stability by their adsorption at the foam lamella which further helped in preventing liquid drainage and film thinning.

New Amphiphilic Tricationic Imidazolium and Pyridinium Ionic Liquids for Demulsification of Arabic Heavy Crude Oil Brine Emulsions

Preparation of new green oilfield chemicals based on ionic liquids (ILs) having higher demulsification efficiency to solve the heavy crude oil brine water emulsions became a target in the petroleum research studies and industry. In the present work, the combination of pyridinium, imidazolium, and hydrophilic or hydrophobic moieties in the chemical structure of ILs has been investigated to improve the surface properties of ILs in both bulk solution and interfaces. Aminopyridine was quaternized with cetylbromide and condensed with glyoxal and 4-hydroxybenzaldehyde in acetic acid to prepare imidazolium-pyridinium bromide acetate ionic liquid (IPy-IL). The phenol group of IPy-IL was etherified with tetraethylene glycol to alter its amphiphilicity and synthesize new amphiphiles (AIPy-IL). Their chemical structure, thermal characteristics, and stabilities were characterized. Their aqueous solution performance in seawater was evaluated to investigate their surface activity, aggregation particle sizes, and surface charges. The demulsification performances of the prepared Arabic heavy crude oil seawater emulsions in the presence of different concentrations of IPy-IL and AIPy-IL were evaluated and proved by interfacial tension, particle size, and demulsification efficiencies at a temperature of 45 °C. The data concluded that AIPy-IL was an effective demulsifier for different crude oil seawater emulsion compositions at a low injection dose and temperature of 100 ppm and 45 °C, which were not report elsewhere.

Temperature-Tuned Faceting and Shape Changes in Liquid Alkane Droplets

Recent extensive studies reveal that surfactant-stabilized spherical alkane emulsion droplets spontaneously adopt polyhedral shapes upon cooling below a temperature T_d while remaining liquid. Further cooling induces the growth of tails and spontaneous droplet splitting. Two mechanisms were offered to account for these intriguing effects. One assigns the effects to the formation of an intradroplet frame of tubules consisting of crystalline rotator phases with cylindrically curved lattice planes. The second assigns the sphere-to-polyhedron transition to the buckling of defects in a crystalline interfacial monolayer, known to form in these systems at some T_s > T_d. The buckling reduces the extensional energy of the crystalline monolayer's defects, unavoidably formed when wrapping a spherical droplet by a hexagonally packed interfacial monolayer. The tail growth, shape changes, and droplet splitting were assigned to the decrease and vanishing of surface tension, γ. Here we present temperature-dependent γ(T), optical microscopy measurements, and interfacial entropy determinations for several alkane/surfactant combinations. We demonstrate the advantages and accuracy of the in situ γ(T) measurements made simultaneously with the microscopy measurements on the same droplet. The in situ and coinciding ex situ Wilhelmy plate γ(T) measurements confirm the low interfacial tension, ≲0.1 mN/m, observed at T_d. Our results provide strong quantitative support validating the crystalline monolayer buckling mechanism.

Characterization and interfacial properties of the surfactant ionic liquid 1-dodecyl-3-methyl imidazolium acetate for enhanced oil recovery

Formulations of ionic liquids and alkalis are promising for enhanced oil recovery.