Enhanced oil recovery performance of gemini surfactant-stabilized nanoemulsions functionalized with partially hydrolyzed polymer/silica nanoparticles

Oil Recovery Improvements Based on Pickering Emulsions Stabilized by Cellulose Nanoparticles and Their Underlying Mechanisms: A Review

The use of nanocellulose (NC)-based Pickering emulsions represents an advancement in chemically enhanced oil recovery (cEOR) methods. The main challenge of cEOR is to develop stable and efficient fluids for applications under reservoir conditions. Pickering emulsions have emerged as a possible solution for stabilizing chemical injection fluids. These emulsions are stabilized by solid particles instead of surfactants and have been the focus of research over the past decade because of their high stability. Although these emulsions present promising solutions, most research has focused on nonbiodegradable inorganic particles, raising concerns about their environmental impact. In this context, nanocellulose (NC) has emerged as an innovative and sustainable alternative due to its biodegradability, abundance, and unique surface chemistry. This contribution presents an exploratory literature review on the use of Pickering emulsions, focusing on nanocellulose in the context of enhanced oil recovery (EOR) as an alternative for fluid stabilization under reservoir conditions. The main mechanisms of oil recovery, such as interfacial tension reduction, in situ crude oil emulsification, capillary disjunction, pressure, and fluid rheological behavior, are discussed. This Review highlights the great potential of nanocellulose-based Pickering emulsions to make EOR processes more sustainable and emphasizes the need for further studies to understand the mechanisms involved. A total of 176 scientific articles were analyzed and evaluated to provide insights and contribute to the advancement of cEOR, in addition to addressing the challenges encountered.

Nanoemulsions Stable against Ostwald Ripening

Ostwald ripening, the dominant mechanism of droplet size growth for an O/W nanoemulsion at high surfactant concentrations, depends on micelles in the water phase and high aqueous solubility of oil, especially for spontaneously formed nanoemulsions. In our study, O/W nanoemulsions were formed spontaneously by mixing a water phase with an oil phase containing fatty alcohol polyoxypropylene polyoxyethylene ether (APE). By monitoring periodically the droplet size of the nanoemulsions via dynamic light scattering, we demonstrated that the formed O/W nanoemulsions are stable against Ostwald ripening, i.e., droplet growth. In contrast, the nanoemulsion droplets grew with the addition of micelles, demonstrating the pivotal role of the presence of micelles in the water phase in the occurrence of Ostwald ripening. The influence of the initial phase of APE, the oil or water phase in which APE is present, on the micelle formation is discussed by the partition coefficient and interfacial adsorption of APE between the oil and water phase using a surface and interfacial tensiometer. In addition, the spontaneously formed O/W nanoemulsion, which is stable against Ostwald ripening, can be used as a nanocarrier for the delivery of water-insoluble pesticides. These results provide a novel approach for the preparation of stable nanoemulsions and contribute to elucidating the mechanism of instability of nanoemulsions.

Microfluidic Methods for Generation of Submicron Droplets: A Review

Submicron droplets are ubiquitous in nature and widely applied in fields such as biomedical diagnosis and therapy, oil recovery and energy conversion, among others. The submicron droplets are kinetically stable, their submicron size endows them with good mobility in highly constricted pathways, and the high surface-to-volume ratio allows effective loading of chemical components at the interface and good heat transfer performance. Conventional generation technology of submicron droplets in bulk involves high energy input, or relies on chemical energy released from the system. Microfluidic methods are widely used to generate highly monodispersed micron-sized or bigger droplets, while downsizing to the order of 100 nm was thought to be challenging because of sophisticated nanofabrication. In this review, we summarize the microfluidic methods that are promising for the generation of submicron droplets, with an emphasize on the device fabrication, operational condition, and resultant droplet size. Microfluidics offer a relatively energy-efficient and versatile tool for the generation of highly monodisperse submicron droplets.

The Synergistic Effects between Sulfobetaine and Hydrophobically Modified Polyacrylamide on Properties Related to Enhanced Oil Recovery

In order to explore the mechanism responsible for the interactions in the surfactant-polymer composite flooding and broaden the application range of the binary system in heterogeneous oil reservoirs, in this paper, the influences of different surfactants on the viscosity of two polymers with similar molecular weights, partially hydrolyzed polyacrylamide (HPAM) and hydrophobically modified polyacrylamide (HMPAM), were studied at different reservoir environments. In addition, the relationship between the surfactant-polymer synergistic effects and oil displacement efficiency was also investigated. The experimental results show that for HPAM, surfactants mainly act as an electrolyte to reduce its viscosity. For HMPAM, SDBS and TX-100 will form aggregates with the hydrophobic blocks of polymer molecules, reducing the bulk viscosity. However, zwitterionic surfactant aralkyl substituted alkyl sulfobetaine BSB molecules can build "bridges" between different polymer molecules through hydrogen bonding and electrostatic interaction. After forming aggregates with HMPAM molecules, the viscosity will increase. The presence of two polymers all weakened the surfactant oil-water interfacial membrane strength to a certain extent, but had little effect on the interfacial tension. The synergistic effect of the "bridge" between HMPAM and BSB under macroscopic conditions also occurs in the microscopic pores of the core, which has a beneficial effect on improving oil recovery.

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.).

Eco-friendly 'ochratoxin A' control in stored licorice roots - quality assurance perspective

According to toxicity data, ochratoxin A (OTA) is the second most important mycotoxin and is produced by Aspergillus and Penicillium. As a natural antifungal agent, clove essential oil (CEO) is a substance generally recognised as safe (GRAS) and shows strong activity against fungal pathogens. Here, we aimed to investigate the control efficacy of CEO in nano-emulsions (CEN) against OTA production in licorice roots and rhizomes during storage. The experiments were performed under simulated conditions of all four seasons (i.e. Spring, Summer, Autumn and Winter). Relative humidity (RH) and temperature were simulated in desiccators along with various salt solutions in incubators. Fresh licorice roots were immersed in CEN at various concentrations (150, 300, 600, 1200 and 2400 µl/l). Before utilising the nano-emulsions, we measured their polydispersity index and mean droplet size by the dynamic light scattering (DLS) technique. Also, the chemical composition of the CEO was determined using GC and GC-MS analyses. Sampling was carried out to monitor OTA once every five days. The samples were dried immediately and analysed by high-performance liquid chromatography (HPLC). Results showed that various concentrations of CEN inhibited the growth of fungi and OTA production. The most effective CEN concentrations were 1200 and 2400 µl/l, which reduced OTA production to 19 and 20 ppb under Winter and Autumn conditions, respectively. These results suggest an effective eco-friendly method for the storage of licorice to reduce postharvest fungal decay.

Characteristics and pH-Responsiveness of SDBS–Stabilized Crude Oil/Water Nanoemulsions

Nanoemulsions are colloidal systems with a wide spectrum of applications in several industrial fields. In this study, crude oil-in-water (O/W) nanoemulsions were formulated using different dosages of the anionic sodium dodecylbenzenesulfonate (SDBS) surfactant. The formulated nanoemulsions were characterized in terms of emulsion droplet size, zeta potential, and interfacial tension (IFT). Additionally, the rheological behavior, long-term stability, and on-demand breakdown of the nanoemulsions via a pH-responsive mechanism were evaluated. The obtained results revealed the formation of as low as 63.5 nm average droplet size with a narrow distribution (33–142 nm). Additionally, highly negative zeta potential (i.e., −62.2 mV) and reasonably low IFT (0.45 mN/m) were obtained at 4% SDBS. The flow-ability of the nanoemulsions was also investigated and the obtained results revealed an increase in the nanoemulsion viscosity with increasing the emulsifier content. Nonetheless, even at the highest SDBS dosage of 4%, the nanoemulsion viscosity at ambient conditions never exceeded 2.5 mPa·s. A significant reduction in viscosity was obtained with increasing the nanoemulsion temperature. The formulated nanoemulsions displayed extreme stability with no demulsification signs irrespective of the emulsifier dosage even after one-month shelf-life. Another interesting and, yet, surprising observation reported herein is the pH-induced demulsification despite SDBS not possessing a pH-responsive character. This behavior enabled the on-demand breakdown of the nanoemulsions by simply altering their pH via the addition of HCl or NaOH; a complete and quick oil separation can be achieved using this simple and cheap demulsification method. The obtained results reveal the potential utilization of the formulated nanoemulsions in oilfield-related applications such as enhanced oil recovery (EOR), well stimulation and remediation, well-bore cleaning, and formation fracturing.

Experimental Research on Seepage Law and Migration Characteristics of Core-Shell Polymeric Nanoparticles Dispersion System in Porous Media

The nanoparticles dispersion system has complex migration characteristics and percolation law in porous media due to the interaction between the nanoparticles and porous media. In this paper, lab experiments were carried out to characterize the morphology, particle size distributions, and apparent viscosities of SiO2/P(MBAAm-co-AM) polymeric nanoparticle solution, investigate its migration characteristics in porous media, and probe its capability of enhanced oil recovery (EOR) in the reservoirs. Quartz microtubule, sand pack, and etched glass micromodels were used as the porous media in the flow and flooding experiments. Gray image-processing technology was applied to achieve oil saturation at different flooding stages in the micromodel for calculating the EOR of the SiO2/P(MBAAm-co-AM) polymeric nanoparticle solution. The results show that The SiO2/P(MBAAm-co-AM) polymeric nanoparticles are spherical with diameters ranging from 260 to 300 nm, and the thicknesses of the polymeric layers are in the range of 30-50 nm. As the swelling time increases from 24 to 120 h, the medium sizes of the SiO2/P(MBAAm-co-AM) polymeric nanoparticles increase from 584.45 to 1142.61 nm. The flow of the SiO2/P(MBAAm-co-AM) polymeric nanoparticles has obvious nonlinear characteristics and a prominent scale effect at a low-pressure gradient, and there should be an optimal matching relationship between its injection mass concentration and the channel size. The flow tests in the sand packs demonstrate that the SiO2/P(MBAAm-co-AM) polymeric nanoparticles can form effective plugging in the main flow channels at different permeability areas and can break through at the throat to fulfill the step-by-step profile control. Moreover, the profile control of the SiO2/P(MBAAm-co-AM) polymeric nanoparticles strengthens with an increase in their swelling time. The microscopic flooding experiment in the etched glass micromodel confirms that the SiO2/P(MBAAm-co-AM) polymeric nanoparticles can block dynamically and alternatively the channels of different sizes with the form of loose or dense networks to adjust the fluid flow diversion, improve the sweep efficiency, and recover more residual oil. The SiO2/P(MBAAm-co-AM) polymeric nanoparticles can achieve an enhanced oil recovery of 20.71% in the micromodel.

Influence of Polymer Viscoelasticity on Microscopic Remaining Oil Production

To investigate the impact of polymer viscoelasticity on microscopic remaining oil production, this study used microscopic oil displacement visualisation technology, numerical simulations in PolyFlow software, and core seepage experiments to study the viscoelasticity of polymers and their elastic effects in porous media. We analysed the forces affecting the microscopic remaining oil in different directions, and the influence of polymer viscoelasticity on the displacement efficiency of microscopic remaining oil. The results demonstrated that the greater the viscosity of the polymer, the greater the deformation and the higher the elasticity proportion. In addition, during the creep recovery experiment at low speed, the polymer solution was mainly viscous, while at high speed it was mainly elastic. When the polymer viscosity reached 125 mPa·s, the core effective permeability reached 100 × 10⁻³ μm², and the equivalent shear rate exceeded 1000 s⁻¹, the polymer exhibited an elastic effect in the porous medium and the viscosity curve displayed an ‘upward’ phenomenon. Moreover, the difference in the normal deviatoric stress and horizontal stress acting on the microscopic remaining oil increased exponentially as the viscosity of the polymer increased. The greater the viscosity of the polymer, the greater the remaining oil deformation. During the microscopic visualisation flooding experiment, the viscosity of the polymer, the scope of the mainstream line, and the recovery factor all increased. The scope of spread in the shunt line area significantly increased, but the recovery factor was significantly lower than that in the mainstream line. The amount of remaining oil in the unaffected microscopic area also decreased.

Tuning the Stability of Liquids by Controlling the Formation of Interfacial Surfactants

Currently, the stability of liquids by nanoparticle surfactants is widely investigated, while the stability of liquids by supramolecular polymer surfactants is rarely involved. Herein, we combine small organic molecules dissolved...

pH-Responsive Nanoemulsions Based on a Dynamic Covalent Surfactant

Developing solid-free nanoemulsions with pH responsiveness is desirable in enhanced oil recovery (EOR) applications. Here, we report the synthesis of an interfacial activity controllable surfactant (T−DBA) through dynamic imine bonding between taurine (T) and p-decyloxybenzaldehyde (DBA). Instead of macroemulsions, nanoemulsions can be prepared by using T−DBA as an emulsifier. The dynamic imine bond of T−DBA enables switching between the active and inactive states in response to pH. This switching of interfacial activity was used to gate the stability of nanoemulsions, thus enabling us to turn the nanoemulsions off and on. Using such dynamic imine bonds to govern nanoemulsion stability could enable intelligent control of many processes such as heavy oil recovery and interfacial reactions.

Progress of polymer gels for conformance control in oilfield

For the past decades, long-term water flooding processes have led to water channeling in mature reservoirs, which is a severe problem in oilfields. The development of better plugging ability and cost-effective polymer gel is a key aspect for the control of excess water production. Research on polymer gel applicable in a heterogeneous reservoir to plug high permeable channels has been growing significantly as revealed by numerous published scientific papers. This review intends to discuss the polymer gel techniques from innovations to applications. The related difficulties and future prospects of polymer gels are also covered. Developments of polymer gels to resist temperature, early gel formation, synergistic mechanisms and influence of pH, high salinity are systematically emphasized. The review provides a basis to develop polymer gels for future applications in oilfields to meet harsh reservoir conditions. It will assist the researchers to further develop polymer gels to improve the oil recovery from mature reservoirs under economic conditions to meet the requirements of future oilfields.