Effect of Imidazolium-Based Ionic Liquids on the Interfacial Tension of the Alkane–Water System and Its Influence on the Wettability Alteration of Quartz under Saline Conditions through Contact Angle Measurements

Effect of the Type and Concentration of Salt on Production Efficiency in Smart Water Injection into Carbonate Oil Reservoir Rocks

Smart waterflooding is one of the most practical emerging methods of enhanced oil recovery in carbonate reservoirs. In this study, the effect of salt type and its concentration in smart water on oil recovery from a carbonate reservoir rock is investigated. A series of experimental measurements, including zeta potential (ZP), interfacial tension (IFT), and contact angle (CA), were conducted to examine the effect of ions on the oil/brine/rock interaction. IFT, ZP, and CA were also used as screening methods to select effective solutions for flooding experiments. The results of the study show that synthesized brines containing sodium acetate and potassium acetate salts have a significant effect on the reduction of IFT; however, rock surface wettability due to such brines is insignificant. The presence of organic salts in the injected water can alter the properties of the fluid and rock surface, leading to improved oil recovery. The salts can reduce the interfacial tension between the oil and water phases, making it easier for the water to displace and mobilize trapped oil. This effect is particularly beneficial in reservoirs with high oil-water interfacial tension as it enhances the capillary forces and improves the sweep efficiency. Smart water with sodium acetate (MSW.NaOAc) caused a 7% increase in oil production in the tertiary injection process due to IFT and CA reduction. The secondary injection of MSW.NaOAc led to an oil production efficiency of 76%, which is 10% higher than that of the secondary injection of seawater (SW), confirming the effectiveness of acetate ions in enhancing oil recovery. Doubling the concentration of sulfate ions in modified SW (MSW.NaOAc.2S) caused a 19% increase in oil production in tertiary injections after SW flooding. The secondary injection of MSW.NaOAc.2S produced a 13% increase in the recovery factor compared to SW flooding in the secondary mode. The main driving mechanism for oil mobilization was found to be wettability alteration, which is supported by the analyses of CA and ZP. This study confirms that the salt type and concentration present in a brine solution play a vital role in the movement of trapped oil in carbonate reservoirs.

Review on Amphiphilic Ionic Liquids as New Surfactants: From Fundamentals to Applications

The demand for lowering interfacial tension (IFT) in different processes has persuaded researchers to use stable and resistant surfactants with low environmental impact. For this purpose, surface-active ionic liquids (SAILs) have attracted much attention owing to their good amphiphilic nature and prominent properties like recyclability and high performance under harsh conditions. This review initially explains how the IFT and critical micelle concentration of different systems vary in the presence of different SAILs with a variety of alkyl chain lengths, head groups, and counter anions. Towards this aim, some physicochemical properties of SAILs as well as the corresponding theoretical aspects of adsorption are considered. Then, recent advances in utilizing SAILs for reducing IFT of different chemical systems are surveyed. Relevantly, the role of important operating parameters of temperature, pH, presence of electrolytes, and the chemical nature of involved phases are adequately discussed. Further, an overview of different SAILs applications in stabilization, separation, and in petroleum industries is scrutinized. To allow better judgment, precise comparisons between different types of SAILs and conventional surfactants are provided. Finally, challenges and possible directions of future research on SAILs are highlighted.

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.

Improvement of Enzymatic Saccharification of Cellulose-Containing Raw Materials Using Aspergillus niger

Enzymatic hydrolysis of cellulose-containing raw materials, using Aspergillus niger, were studied. Filter paper, secondary cellulose-containing or starch-containing raw materials, miscanthus cellulose after alkaline or acid pretreatment, and wood chip cellulose, were used as substrates. The study focused on a wild A. niger strain, treated, or not (control), by ultraviolet (UV) irradiations for 45, 60, or 120 min (UV45, UV60, or UV120), or by UV irradiation for 120 min followed by a chemical treatment with NaN3 + ItBr for 30 min or 80 min (UV120 + CH30 or UV120 + CH80). A mixture of all the A. niger strains (MIX) was also tested. A citrate buffer, at 50 mM, wasthe most suitable for enzymatic hydrolysis. As the UV exposure time increased to 2 h, the cellulase activity of the surviving culturewas increased (r = 0.706; p < 0.05). The enzymatic activities of the obtained strains, towards miscanthus cellulose, wood chips, and filter paper, were inferior to those obtained with commercial enzymes (8.6 versus 9.1 IU), in some cases. Under stationary hydrolysis at 37 °C, pH = 4.7, the enzymatic activity of A. niger UV120 + CH30 was 24.9 IU. The enzymatic hydrolysis of secondary raw materials, using treated A. niger strains, was themost effective at 37 °C. Similarly, the most effective treatment of miscanthus cellulose and wood chips occurred at 50 °C. The maximum conversion of cellulose to glucose was observed using miscanthus cellulose (with alkaline pretreatment), and the minimum conversion was observed when using wood chips. The greatest value of cellulase activity was evidenced in the starch-containing raw materials, indicating that A. niger can ferment not only through cellulase activity, but also via an amylolytic one.

Synthesis and application of hydrophilically-modified Fe3O4 nanoparticles in oil sands separation

Nanoparticles have been reported to be a promising candidate for the separation of heavy oil from its host rock's surface. These nanoparticles (NPs) are often dispersed and stabilized in the solution by some surfactants during the unconventional oil ores processing. Herein, the PEG600–KH560 (PK) has been grafted onto Fe₃O₄ NP surfaces, obtaining a kind of hydrophilically-modified recyclable nanoparticle. Results show that these NPs (averaged at around 16 nm for single sphere) could be well dispersed in water (no settling in 72 h), forming PK-Fe₃O₄ nanofluids (NFs) at 0.2 wt%. These PK-Fe₃O₄ NFs are found to be able to be quickly separated from the dispersions by an external magnetic field, and returning back to stable NFs when the magnetic field disappears and by shaking. The PK-Fe₃O₄ NFs have been further used for the enhancement of heavy oil recovery from oil sands. The floatation results show that the PK-Fe₃O₄ NFs could improve oil recovery by at least 12% compared with the traditional hot water extraction process (HWEP). After the extraction, up to 70% of the PK-Fe₃O₄ NPs could be directly recycled from the solution for further use. The rest of the NPs are left in the oil phase and attached on the residual solid surface. However, the efficiency of the PK-Fe₃O₄ NPs is found to be decreased when the recycling times exceed 5 due to the adsorption of oil components. A mechanistic study shows that the hydrophilic PK-Fe₃O₄ NPs could be adsorbed on the mineral surface, making the surface more hydrophilic. The hydrophilic surface and the agitation disturbance helps the liberation process of bitumen from the solid surfaces. On the other hand, when adding the PK-Fe₃O₄ NPs into the heavy oil–water system, the oil–water interface is found to be highly modified by the NPs, resulting in significant reduction of the oil–water interfacial tension. The above findings suggest that the PK-Fe₃O₄ NPs combined the surface-active role (surfactant) and the nano-size role (adsorption) together, which facilitates its role in oil sands separation.

A new kind of hydrophilic magnetic nanoparticle has been synthesized and investigated for the performance in floatation experiments.