Stability Mechanism of Nitrogen Foam in Porous Media with Silica Nanoparticles Modified by Cationic Surfactants

Experimental Investigations and MD Simulation on Nanoparticle-Enhanced CO2-Responsive Foam (NECRF): Implications on CO2-EOR

CO2-responsive foam (CRF) is a highly promising candidate for CO2-enhanced oil recovery (CO2-EOR) because it displays higher stability than the surfactant-stabilized foam owing to the formation of robust wormlike micelles (WLMs) upon exposure to CO2. In this work, the nanoparticle-enhanced CO2-responsive foam (NECRF) was properly prepared using lauryl ether sulfate sodium (LES)/diethylenetriamine/nano-SiO2, and its interfacial properties and EOR potential were experimentally and numerically assessed, aiming to explore the feasibility and effectiveness of NECRF as a novel CO2-EOR technique. It was found that the interfacial expansion elastic modulus increased 6-fold after CO2 stimulation. The modulus continued to increase with the introduction of nano-SiO2 owing to the pronounced synergistic effect of WLMs and nanoparticles. In addition to increasing the viscosity of the foaming liquid, WLMs and nano-SiO2 enhanced the shearing resistance of the NECRF as well. Calculations demonstrated that both the coarsening rate and the size distribution uniformity coefficient of NECRF were markedly lower than that of the LES foam, which subsequently inhibited NECRF decay and greatly improved its dynamic stability. Besides, molecular dynamics simulation revealed that adding inorganic salts to NECRF could notably enhance the foaming performance due to the intensified hydration of surfactant head groups and reduced binding energy of neighboring molecules. Nuclear magnetic resonance-assisted core flooding experiments validated the exceptional capacity of NECRF to sweep the low-permeability region and improve the conformance profile. Overall, these findings may provide valuable insights into the development and application of novel materials and strategies for the CO2-EOR.

Maximizing oil recovery: Innovative chemical EOR solutions for residual oil mobilization in Kazakhstan's waterflooded sandstone oilfield

The results of an experimental study to design a chemical flood scheme for a massive Kazakhstani oilfield with high water cut are presented in this paper. A meticulously formulated chemical flooding procedure entails injecting a blend comprising interfacial tension (IFT) reducing agents, alkaline/nanoparticles to control chemical adsorption, and polymer to facilitate mobility control. Overall, this well-conceived approach leads to a significant enhancement in the mobilization and production of residual oil. Experiments were conducted in Kazakhstan's Field A, one of the country's oldest oilfields with over 90% water cut and substantial remaining oil, to assess the efficiency of various hydrolyzed polyacrylamide (HPAM) derived polymers and surfactant solutions. Additionally, the effectiveness of alkaline and nanoparticles in minimizing chemical adsorption for the screened surfactant and polymer was investigated. These assessments were conducted under reservoir conditions, with a temperature of 63 °C, and using 13,000 ppm Caspian seawater as makeup brine. The performance assessment of the selected chemicals was carried out through a set of oil displacement tests on reservoir cores. Critical parameters, including chemical adsorption, interfacial tension, resistance factor, and oil recovery factor, were compared to determine the most effective chemical flooding approach for Field A. Both the surfactant-polymer (SP) and alkali-surfactant-polymer (ASP) approaches were more successful in recovering residual oil by efficiently generating and delivering microemulsion, producing more than 90% of the remaining oil after waterflooding. Due to the low increase in recovery compared to SP and the complexity of applying ASP at the field scale, SP was recommended for the pilot test studies. This investigation underscores that the choice of chemicals is contingent upon the interplay between the specific characteristics of the oil, the geological formation, the injection water, and the reservoir rock. Consequently, assessing all potential configurations on reservoir cores is imperative to identify the most optimal chemical combination. The practical challenges at the field scale should also be considered for the final decision. The results of this study contribute to the successful design and implementation of tailored chemical flooding to challenging oilfields with excessive water cut and high residual oil.

Demystifying the Role of Surfactant in Tailoring Polyamide Morphology for Enhanced Reverse Osmosis Performance: Mechanistic Insights and Environmental Implications

Surfactant-assisted interfacial polymerization (IP) has shown strong potential to improve the separation performance of thin film composite polyamide membranes. A common belief is that the enhanced performance is attributed to accelerated amine diffusion induced by the surfactant, which can promote the IP reaction. However, we show enhanced membrane performance for Tween 80 (a common surfactant), even though it decreased the amine diffusion. Indeed, the membrane performance is closely related to its polyamide roughness features with numerous nanovoids. Inspired by the nanofoaming theory that relates the roughness features to nanobubbles degassed during the IP reaction, we hypothesize that the surfactant can stabilize the generated nanobubbles to tailor the formation of nanovoids. Accordingly, we obtained enlarged nanovoids when the surfactant was added below its critical micelle concentration (CMC). In addition, both the membrane permeance and selectivity were enhanced, thanks to the enlarged nanovoids and reduced defects in the polyamide layer. Increasing the concentration above CMC resulted in shrunken nanovoids and deteriorated performance, which can be ascribed to the decreased stabilization effect caused by micelle formation. Interestingly, better antifouling performance was also observed for the surfactant-assisted membranes. Our current study provides mechanistic insights into the critical role of surfactant during the IP reaction, which may have important implications for more efficient membrane-based desalination and water reuse.

Synthesis and stability of switchable CO2-responsive foaming coupled with nanoparticles

CO₂-responsive foaming has been drawing huge attention due to its unique switching characteristics in academic research and industrial practices, whereas its stability remains questionable for further applications. In this paper, a new CO₂-switchable foam was synthesized by adding the preferably selected hydrophilic nanoparticle N20 into the foaming agent C₁₂A, through a series of analytical experiments. Overall, the synergy between cationic surfactants and nanoparticles with a contact angle of 37.83° is the best. More specifically, after adding 1.5 wt% N20, the half-life of foam is 14 times longer than that of pure C₁₂A foam. What’s more, the C₁₂A-N20 solution is validated to own distinctive CO₂-N₂ switching features because very slight foaming degradations are observed in terms of the foaming volume and half-life time even after three cycles of CO₂-N₂ injections. This study is of paramount importance pertaining to future CO₂ foam research and applications in energy and environmental practices.

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Cationic surfactants have the best synergy with NPs with a contact angle of 37.83°

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The foam stability increased with the increase of NPs concentration

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CO₂/N₂ can control the foaming properties of C₁₂A-N20 solution and are reversible

pH-responsive pickering foam created from self-aggregate polymer using dynamic covalent bond

HYPOTHESIS

Responsive surfactant systems based on dynamic covalent bond exhibit an unsatisfactory foamability and foam stability, despite their documented functionality in emulsions. As such we anticipate that the foaming performance should be improved by introducing Pickering effect, which is possible when the responsiveness of the dynamic covenant bonds controls not only the hydrophobicity of polymers but also their aggregation behavior (to form nanoparticles).

EXPERIMENTS

Here we created surface active nanoparticles made from self-aggregated polymers consisting of PAH (polyallylamine hydrochloride)-BA (benzaldehyde). The covalent imine bonds between originally hydrophilic PAH and hydrophobic BA are dynamic in that their formation and breakage is a function of solution pH, confirmed by ¹H NMR and dynamic interfacial tension measurement.

FINDINGS

At pH 7.4, a stable foam is achieved in the PAH-BA (amino to aldehyde ratio at 1:0.2) solution; while at pH 2.5, it defoams due to breakage of dynamic bonds corresponding to the measured diminishing surface activity. The reversibility of foaming-defoaming has been demonstrated by alternatively changing pH for multiple cycles, with the foaming performance persistent. The foam stability can be improved by more hydrophobic compounds e.g. at a lower amino to aldehyde ratio or using PAH-cinnamaldehyde (CA). The reversible and responsive foaming demonstrated in a Pickering system provides a new method to create novel foaming systems with properties desirable to many applications.

Different strategies of foam stabilization in the use of foam as a fracturing fluid

An attractive alternative to mitigate the adverse effects of conventional water-based fluids on the efficiency of hydraulic fracturing is to inject foam-based fracking fluids into reservoirs. The efficiency of foaming fluids in subsurface applications largely depends on the stability and transportation of foam bubbles in harsh environments with high temperature, pressure and salinity, all of which inevitably lead to poor foam properties and thus limit fracturing efficiency. The aim of this paper is to elaborate popular strategies of foam stabilization under reservoir conditions. Specifically, this review first discusses three major mechanisms governing foam decay and summarizes recent progress in research on these phenomena. Since surfactants, polymers, nanoparticles and their composites are popular options for foam stabilization, their stabilizing effects, especially the synergies in composites, are also reviewed. In addition to reporting experimental results, the paper also reports recent advances in interfacial properties via molecular dynamical simulation, which provide new insights into gas/liquid interfacial properties under the influence of surfactants at molecular scale. The results of both experiments and simulations indicate that foam additives play an essential role in foam stability and the synergic effects of surfactants and nanoparticles exhibit more favorable performance.