Surfactant-Augmented Functional Silica Nanoparticle Based Nanofluid for Enhanced Oil Recovery at High Temperature and Salinity

γ-Cyclodextrin-based metal-organic frameworks for lactonic sophorolipid application in enhanced oil recovery

Lactonic sophorolipid (LSL) exhibits numerous surfactant activities, such as emulsification, wetting action, dispersion effect, and oil-washing activities. Nevertheless, LSLs have poor water solubility, which restrains their application in the petroleum industry. In this research, a new compound, lactonic sophorolipid cyclodextrin metal-organic framework (LSL-CD-MOFs), was obtained by loading LSL into γ-cyclodextrin metal-organic frameworks (γ-CD-MOFs). The LSL-CD-MOFs were characterized by N₂ adsorption analysis, X-ray powder diffraction analysis, Fourier transform infrared spectroscopy, and thermogravimetric analysis. Loading LSL into γ-CD-MOFs significantly increased the apparent water solubility of LSL. However, the critical micelle concentration of LSL-CD-MOFs was similar to that of LSL. Furthermore, LSL-CD-MOFs effectively reduced the viscosities and improved the emulsification indices of oil-water mixtures. Oil-washing tests, which were conducted using oil sands, revealed that the LSL-CD-MOFs yielded an oil-washing efficiency of 85.82 % ± 2.04 %. Overall, γ-CD-MOFs are promising carriers for LSL, and LSL-CD-MOFs are a potential, low-cost, new, green surfactant for enhanced oil recovery.

Probing the Mechanism of Targeted Delivery of Molecular Surfactants Loaded into Nanoparticles after Their Assembly at Oil-Water Interfaces

A targeted and controlled delivery of molecular surfactants at oil-water interfaces using the directed assembly of nanoparticles, NPs, is reported. The mechanism of NP assembly at the interface and the release of molecular surfactants is followed by laser scanning confocal microscopy and surface force spectroscopy. The assembly of positively charged polystyrene NPs at the oil-water interface was facilitated by the introduction of carboxylic acid groups in the oil phase (e.g., by adding 1 wt % stearic acid to hexadecane to produce a model oil). The presence of positively charged NPs consistently lowers the stiffness of the water-oil interface. The effect is lessened, when the NPs are present in a solution of NaCl or deionized water at pH 2, consistent with a less dense monolayer of NPs at the interface in the last two systems. In addition, the NPs reduce the interfacial adhesion (i.e., the "stickiness" of the interface or, put differently, the pull-off force experienced by the atomic force microscopy (AFM) tip during retraction). After the assembly, the NPs can release a previously loaded cargo of surfactant molecules, which then facilitate the formation of a much finer oil-water emulsion. As a proof of concept, we demonstrate the release of octadecyl amine, ODA, that has been incorporated into the NPs prior to the assembly. The release of ODA causes the NPs to detach from the interface altering the interfacial properties and leads to finer oil droplets. This approach can be exploited in applications in several fields ranging from pharmaceutical and cosmetics to hydrocarbon recovery and oil-spill remediation, where a targeted and controlled release of surfactants is wanted.

Nanoparticles in Chemical EOR: A Review on Flooding Tests

The use of nanofluids is showing promise as an enhanced oil recovery (EOR) method. Several reviews have been published focusing on the main mechanisms involved in the process. This new study, unlike previous works, aims to collect information about the most promising nano-EOR methods according to their performance in core-flooding tests. As its main contribution, it presents useful information for researchers interested in experimental application of nano-EOR methods. Additional recoveries (after brine flooding) up to 15% of the original oil in place, or higher when combined with smart water or magnetic fields, have been found with formulations consisting of simple nanoparticles in water or brine. The functionalization of nanoparticles and their combination with surfactants and/or polymers take advantage of the synergy of different EOR methods and can lead to higher additional recoveries. The cost, difficulty of preparation, and stability of the formulations have to be considered in practical applications. Additional oil recoveries shown in the reviewed papers encourage the application of the method at larger scales, but experimental limitations could be offering misleading results. More rigorous and systematic works are required to draw reliable conclusions regarding the best type and size of nanoparticles according to the application (type of rock, permeability, formation brine, reservoir conditions, other chemicals in the formulation, etc.).

A Critical Overview of ASP and Future Perspectives of NASP in EOR of Hydrocarbon Reservoirs: Potential Application, Prospects, Challenges and Governing Mechanisms

Oil production from depleted reservoirs in EOR (Enhanced Oil Recovery) techniques has significantly increased due to its huge demands in industrial energy sectors. Chemical EOR is one of the best approaches to extract the trapped oil. However, there are gaps to be addressed and studied well for quality and cost consideration in EOR techniques. Therefore, this paper addresses for the first time a systematic overview from alkaline surfactant polymer ((ASP)) and future perspectives of nano-alkaline surfactant polymer ((NASP)), its synergy effects on oil recovery improvement, and the main screening criteria for these chemicals. The previous findings have demonstrated that the optimum salinity, choosing the best concentration, using effective nano-surfactant, polymer and alkaline type, is guaranteed an ultra-low IFT (Interfacial Tension). Core flood results proved that the maximum oil is recovered by conjugating nanoparticles with conventional chemical EOR methods (surfactant, alkaline and polymer). This work adds a new insight and suggests new recommendation into the EOR application since, for the first time, it explores the role and effect of nanotechnology in a hybrid with ASP. The study illustrates detailed experimental design of using NASP and presents an optimum micro-model setup for future design of NASP flow distribution in the porous media. The presence of nano along with other chemicals increases the capillary number as well as the stability of chemicals in the solution and strengthens the effective mechanisms on the EOR.

Spontaneous Imbibition Oil Recovery by Natural Surfactant/Nanofluid: An Experimental and Theoretical Study

Organic surfactants have been utilized with different nanoparticles in enhanced oil recovery (EOR) operations due to the synergic mechanisms of nanofluid stabilization, wettability alteration, and oil-water interfacial tension reduction. However, investment and environmental issues are the main concerns to make the operation more practical. The present study introduces a natural and cost-effective surfactant named Azarboo for modifying the surface traits of silica nanoparticles for more efficient EOR. Surface-modified nanoparticles were synthesized by conjugating negatively charged Azarboo surfactant on positively charged amino-treated silica nanoparticles. The effect of the hybrid application of the natural surfactant and amine-modified silica nanoparticles was investigated by analysis of wettability alteration. Amine-surfactant-functionalized silica nanoparticles were found to be more effective than typical nanoparticles. Amott cell experiments showed maximum imbibition oil recovery after nine days of treatment with amine-surfactant-modified nanoparticles and fifteen days of treatment with amine-modified nanoparticles. This finding confirmed the superior potential of amine-surfactant-modified silica nanoparticles compared to amine-modified silica nanoparticles. Modeling showed that amine surfactant-treated SiO₂ could change wettability from strongly oil-wet to almost strongly water-wet. In the case of amine-treated silica nanoparticles, a strongly water-wet condition was not achieved. Oil displacement experiments confirmed the better performance of amine-surfactant-treated SiO₂ nanoparticles compared to amine-treated SiO₂ by improving oil recovery by 15%. Overall, a synergistic effect between Azarboo surfactant and amine-modified silica nanoparticles led to wettability alteration and higher oil recovery.

Recent advances of biosurfactant for waste and pollution bioremediation: Substitutions of petroleum-based surfactants

Biosurfactant is one of the emerging compounds in the industrial sector that behaves similarly with their synthetic counterparts, as they can reduce surface and interfacial tension between two fluids. Their unique properties also enable biosurfactant molecules to be able to clump together to form micelles that can capture targeted molecules within a solution. Biosurfactants are compared with synthetic surfactants on various applications for which the results shows that biosurfactants are fully capable of replacing synthetic surfactants in applications including enhanced oil recovery and wastewater treatment applications. Biosurfactants are able to be used in different applications as well since they are less toxic than synthetic surfactants. These applications include bioremediation on oil spills in the marine environment and bioremediation for contaminated soil and water, as well as a different approach on the pharmaceutical applications. The future of biosurfactants in the pharmaceutical industry and petroleum industry as well as challenges faced for implementing biosurfactants into large-scale applications are also discussed at the end of this review.

Direct Pore-Level Visualization and Verification of In Situ Oil-in-Water Pickering Emulsification during Polymeric Nanogel Flooding for EOR in a Transparent Three-Dimensional Micromodel

Different from inorganic nanoparticles, nanosized cross-linked polymeric nanoparticles (nanogels) have been demonstrated to generate more stable Pickering emulsions under harsh conditions for a long term owing to their inherent high hydrophilicity and surface energy. In both core and pore scales, the emulsions are found to be able to form in situ during the nanofluid flooding process for an enhanced oil recovery (EOR) process. Due to the limitation of direct visualization in core scale or deficient pore geometries built by two-dimensional micromodels, the in situ emulsification by nanofluids and emulsion transport are still not being well understood. In this work, we use a three-dimensional transparent porous medium to directly visualize the in situ emulsification during the nanogel flooding process for EOR after water flooding. By synthesizing the nanogel with a fluorescent dye, we find the nanogels adsorbed on the oil-water interface to lower the total interfacial energy and emulsify the large oil droplets into small Pickering oil-in-water emulsions. A potential mechanism for in situ emulsification by nanogels is proposed and discussed. After nanogel flooding, the emulsions trapped in pore throats and those in the effluents are all found encapsulated by the nanogels. After nanogel flooding under different flow rates, the sphericity and diameter changes of remaining oil droplets are quantitatively compared and analyzed using grouped boxplots. It is concluded that in situ emulsification happens during nanogel injection due to the reduction of interfacial tension, which helps to increase the oil recovery rate under different flow rates and pore geometries.

Surfactants Enhanced Heavy Oil-Solid Separation from Carbonate Asphalt Rocks-Experiment and Molecular Dynamic Simulation

In this study, surfactants were used to enhance heavy oil-solid separation, and a detailed mechanism was explored by SARA (saturates, aromatics, resins, asphaltenes) analysis, element analysis, AFM measurement, and molecular dynamic simulation. Surfactants could effectively decrease oil/solid interaction force and then oil-solid separation would be enhanced. The oil-solid interactive force was in relation to surfactants concentration, pH value, asphaltene content, and salinity. The molecular dynamics simulation results show that the dissociation of saturated hydrocarbon, aromatic hydrocarbon, resin, and asphaltene (SARA) on carbonate minerals is gradually weakened for all surfactants. In the process of molecular dynamics simulation of surfactant stripping SARA, firstly, the surfactant molecules adsorb on the surface of SARA molecules. After that, the surfactant peels SARA molecules off the surface of calcite under the influence of molecular thermal motion. In this process, surfactant molecules will not be directly adsorbed on the surface of trace minerals. The results of energy/temperature balance indicated that saturates, aromatics and resins could remain stable when the molecular dynamics simulation time reached 2000 ps with the phenomenon that saturates, aromatics could liberate from minerals totally within 2000 ps. The molecular dynamics simulation of asphaltenes will not liberate from calcite surface within 6000 ps, meanwhile, they could not reach the energy balance/energy balance within 6000 ps. The functional groups of surfactant molecules would have interactions with the SARA functional group, resulting in different dissociation effects of SARA. The results of molecular dynamics simulation are consistent with the experiment results. The separation effect of saturated hydrocarbon, aromatic hydrocarbon, resin, and asphaltene in five kinds of surfactants were different. The molecular dynamic simulation results were in accordance with the SARA analysis.

Stimuli-Responsive, Hydrolyzable Poly(Vinyl Laurate-co-vinyl Acetate) Nanoparticle Platform for In Situ Release of Surfactants

A stimuli-responsive, sub-100 nm nanoparticle (NP) platform with a hydrolyzable ester side chain for in situ generation of surfactants is demonstrated. The NPs were synthesized via copolymerization of vinyl-laurate and vinyl-acetate [p-(VL-co-VA), 3:1 molar ratio] and stabilized with a protective poly(ethylene-glycol) shell. The NPs are ∼55 nm in diameter with a zeta potential of -54 mV. Hydrolysis kinetics in an accelerated, base-catalyzed reaction show release of about 11 and 30% of the available surfactant at 25 and 80 °C, respectively. The corresponding values in seawater are 22 and 76%. The efficiency of the released surfactant in reducing the interfacial tension, altering wettability, and stabilizing oil-water emulsion was investigated through contact angle measurements and laser confocal scanning microscopy and benchmarked to sodium laurate, a commercially available surfactant. All these measurements demonstrate both the efficacy of the NP system for surfactant delivery and the ability of the released surfactant to alter wettability and stabilize an oil-water emulsion.

Cooperative Effects Dominating the Thermodynamics and Kinetics of Surfactant Adsorption in Porous Media: From Lateral Interactions to Surface Aggregation

Surfactant adsorption in porous media remains poorly understood, as the microscopic collective behavior of these amphiphilic molecules leads to nonconventional phenomena with complex underlying kinetics/structural organization. Here, we develop a simple thermodynamic model, which captures this rich behavior by including cooperative effects to account for lateral interactions between adsorbed molecules and the formation of ordered or disordered self-assemblies. In more detail, this model relies on a kinetic approach, involving adsorption/desorption rates that depend on the surfactant surface concentration to account for facilitated or hindered adsorption at different adsorption stages. Using different surfactants/porous solids, adsorption on both strongly and weakly adsorbing surfaces is found to be accurately described with parameters that are readily estimated from available adsorption experiments. The validity of our physical approach is confirmed by showing that the inferred adsorption/desorption rates obey the quasi-chemical approximation for lateral adsorbate interactions. Such cooperative effects are shown to lead to adsorption kinetics that drastically depart from conventional frameworks (e.g., Henry, Langmuir, and Sips models).

Core-Shell Nanohydrogels with Programmable Swelling for Conformance Control in Porous Media

Conformance control during waterflooding in an oil reservoir is utilized to redistribute water and increase the sweep efficiency and hence oil production. Using preformed gel particles can effectively redirect the flow by blocking the high-permeability zones and forcing water into low-permeability zones where the oil is trapped. However, the size of such gel particles can limit their applications deeper within the reservoir and can result in shear-induced degradation near the well bore. Here, we fabricate core-shell nanohydrogels with delayed swelling behavior; their volume increases by a factor of 200 after about 30 days in brine under reservoir conditions. We study their effect on the flow behavior in a three-dimensional porous medium micromodel consisting of randomly packed glass beads. Using confocal microscopy, we directly visualize the spatial variations of flow in the micromodel before and after nanohydrogel injection and swelling. The swollen nanohydrogels block some pores reducing the permeability of the micromodel and diverting the water into low-permeability regions. A core flood experiment further confirms that the nanohydrogels can significantly reduce the permeability of a reservoir sample and divert the fluid flow. Our results demonstrate that these core-shell nanohydrogels might be useful for flow control in porous media and can be used as a conformance control agent.