Surfactant Foam Research Articles

Effect of gas type on properties of anionic surfactant foam system

The foam drainage technique is considered to be a promising measure for solving the problem of liquid accumulation in natural gas wells and gathering pipelines. However, differences in gases can greatly affect the performance of surfactant foam, thus limiting the application of this technology. To elucidate the mechanism of natural gas components influencing foam properties, the interfacial properties of hydrocarbon gas-surfactant-water system were analyzed thermodynamically and kinetically by combining molecular dynamics simulations and foaming experiments. The results show that with the increasing alkane chain length, the foaming volume and half-life of the foam are gradually rising, while the gas–liquid interfacial tension is decreasing, which is consistent with the results of molecular dynamics simulations. Compared with air, hydrocarbon gases are more beneficial for foam generation and stabilization. The interfacial adsorption of alkane molecules and the interaction between alkanes and surfactants are the main factors affecting the interfacial tension and film stability of different systems.

Integration between experimental investigation and numerical simulation of alkaline surfactant foam flooding in carbonate reservoirs

In Brazil, pre-salt carbonate reservoirs are largely responsible for the current increase in oil production. However, due to its peculiar characteristics, increasing oil recovery by water injection is not enough. Therefore, we seek to evaluate the recovery potential using chemical methods (cEOR). Among these, the Alkali Surfactant Foam (ASF) method appears with high potential, a variant of Alkali Surfactant Polymers (ASP) without the problems presented by it. Therefore, this work presents an innovative methodology, which seeks to evaluate the potential for recovery with ASF in carbonate reservoirs by integrating experimental characterization and recovery prediction using reservoir simulation. For this, phase behavior and adsorption analyses were carried out. The experimental results provided key parameters for the simulation, such as optimal salinity, surfactant adsorption, foam mobility reduction factors. The results are from two case studies of AS and ASF flooding, using a section of UNISIM-II benchmark, using a one-quarter of five-spot model. Having the modelling for these cEOR methods defined, an optimization process for each method was applied, allowing a reliable comparison among the methods and over a base case of water injection, seeking the maximization of the net present value (NPV). As a result, in the experimental part, a low interfacial tension (IFT) value of 0.003 mN/m was achieved with a surfactant adsorption reduction of 17.9% for an optimal setting among brine (NaCl), alkali (NaBO2.4H2O), and surfactant (BIO-TERGE AS 40). In the reservoir simulation part, using a fast genetic algorithm in the optimization process, a NPV of US$ 14.43 million higher than the base case (water injection) and a 4.5% increase in cumulative oil production for the ASF injection case were obtained. Considering the analyses of production curves (cumulative oil production and oil rate) and oil saturation maps, a considerable oil production anticipation was observed, which was the main reason for NPV improvement, proving the high potential for application of the ASF method in carbonate reservoirs.

Influence of carbon quantum dots on foam stability: a molecular dynamics study

Abstract Carbon quantum dots are employed in foam for enhanced oil recovery. This study focuses on the impact of carbon quantum dots on the stability of oil displacement foam. Molecular dynamics simulations are conducted to investigate commonly used models of carbon quantum dots and surfactant foams in oil displacement. The research delves into the interfacial properties of the foam film, the flow characteristics of water molecules, and the interaction between carbon quantum dots and surfactants. Insights gained from these three aspects reveal the influence of carbon quantum dots on surfactant foam films. This work provides theoretical guidance for the utilization of carbon nanomaterials in foam-assisted oil recovery.

SDS and TX-100 performance in removing Cd ion from contaminated sand in flushing column

In this study, contaminated sand by cadmium (Cd2+) ion was cleansed by surfactant foam in a flushing column. The ability to remove Cd2+ ion on the sand surface influenced by the surfactant's properties. The Sodium dodecyl sulfate (SDS) as an anionic surfactant was compared with Triton X-100 (TX-100) non anionic surfactant in their ability to remove the metal ion on the sand surface in the flushing column. The loading time, surfactant concentration, and flow rate of the surfactant were then investigated to confirm the charging effect of surfactant in the ability to remove metal ions. The results show that SDS has a higher ability than TX-100 to remove the Cd2+ ion on the sand surface. The optimal removal efficiency by SDS was 52 %, and TX 100 was 47 %. The loading time impacted surfactant interaction with metal ions in the column, showing that a longer loading time will increase the removal efficiency. Increased concentration of surfactants and more prolonged initial flushing tend to remove higher metal ions, indicating that the residual metal ion was flushing out on the first four pore volume removals. Flushing in a column with foam by anionic surfactant shows a higher ability to remove metal ions on the sand surface.

An experimental study of foam-oil interactions for nonionic-based binary surfactant systems under high salinity conditions

A key factor affecting foam stability is the interaction of foam with oil in the reservoir. This work investigates how different types of oil influence the stability of foams generated with binary surfactant systems under a high salinity condition. Foam was generated with binary surfactant systems, one composed of a zwitterionic and a nonionic surfactant, and the other composed of an anionic and a nonionic surfactant. Our results showed that the binary surfactant foams investigated are more tolerant under high salinity conditions and in the presence of oil. This was visually observed in our microscopic analysis and was further attributed to an increase in apparent viscosity achieved with binary surfactant systems, compared to single surfactant foams. To understand the influence of oil on foam stability, we performed a mechanistic study to investigate how these oils interact with foams generated with binary surfactants, focusing on their applicability under high salinity conditions. The generation and stability of foam are linked to the ability of the surfactant system to solubilize oil molecules. Oil droplets that solubilize in the micelles appear to destabilize the foam. However, oils with higher molecular weights are too large to be solubilized in the micelles, hence the molecules will have less ability to be transported out of the foam, so oil seems to stabilize the foam. Finally, we conducted a multivariate analysis to identify the parameters that influenced foam stability in different oil types, using the experimental data from our work. The results showed that the oil molecular weight, interfacial tension between the foaming liquid and the oil, and the spreading coefficient are the most important variables for explaining the variation in the data. By performing a partial least square regression, a linear model was developed based on these most important variables, which can be used to predict foam stability for subsequent experiments under the same conditions as our work.

Design of fluorine-free foam extinguishing agent with high surface activity, foam stability and pool fire suppression by optimization of surfactant composition and foam system

To meet the environmental requirement of foam extinguishing agent, a novel fluorine-free surfactant named amino-terminated polyether modified silicone (ATPMS) was successfully synthesized, and then in combination with hydrocarbon surfactant prepared fluorine-free foam extinguishing agent. The study carefully investigated surface tension, foamability, foam stability and fire extinguishing performance of fluorine-free foam extinguishing agent. The results indicate that ATPMS has a low surface tension of 21.17 mN/m, which combined with hydrocarbon surfactant at the mass concentration ratio of 1:1 imparts high surface activity. The sodium lauryl ether sulfate (AES)/ATPMS system owes the optimal comprehensive performance with an initial foam height value of 85.8 mm, a surface tension value of 24.76 mN/m and a foam stability value (the ratio of foam height between initial foam and five-minute foam) of 64.0 % at critical micelle concentration (CMC), respectively. Fire suppression test shows that the obtained fluorine-free foam extinguishing agent is effective in fighting diesel pool fires. The firefighting efficiency of foam agent links to the mixing chamber structure of compressed air foam fire extinguishing system (CAFS). When the mixing chamber of CAFS has a recurrent segment length of 50 mm and the filled particle size of 10 mm, the firefighting efficiency of fluorine-free foam extinguishing agent is optimal with a fire extinguishing time of 33 s and a temperature drop rate of 6.49 °C/s.

Surfactant foam injection for remediation of diesel-contaminated soil: A comprehensive study on the role of co-surfactant in foaming formulation enhancement

Aqueous foam injection is a promising technique for in-situ remediation of soil and aquifers contaminated by petroleum products. However, the application efficiency is strongly hindered by foam's instability upon contact with hydrocarbons. Addressing this, we propose a new binary surfactant mixture of Sodium Dodecyl Sulfate (SDS) and Cocamidopropyl Hydroxysultaine (CAHS). This study investigates CAHS's role as a co-surfactant in enhancing foam stability against antifoaming diesel oil under static and dynamic conditions. Using a dynamic foam analyzer (DFA-100), we assessed static foam's stability by monitoring decay profiles and bubble growth over time. The results revealed that the highest stability can be reached at a CAHS to SDS ratio of 50:50, increasing the half-life of the foam by 7.7 times. Remarkably, our analyses at bulk and bubble scales also elucidated the mechanisms behind the enhanced foam stability of the proposed binary surfactant mixture in the absence and presence of diesel. Additionally, in a 1D sand column, the SDS-CAHS mixture demonstrated more than twofold improvement of the Resistance Factor, attributed to the better survival of the lamellae due to the reduced rate of their destruction. This formulation also yielded a recovery improvement of >10 % compared to SDS foam. The significant improvements in stability and performance of the SDS-CAHS (50:50) mixture were credited to a robust pseudo-emulsion film formation, creating a higher oil entry barrier. This reinforcement and the surfactant molecules' synergistic interactions at the gas-liquid-oil interface significantly contributed to the overall effectiveness.

Investigation on foam properties of Gemini quaternary ammonium salt containing hydroxyl hydrophilic headgroup

Four Gemini quaternary ammonium salts, tetramethylene-1,4- bis [N, N-bis(hydroxypropyl)-hexa/decyloxypropylammonium] bromide (GC6/10-P) and tetramethylene-1,4-bis [N, N-bis(hydroxyethyl)-hexa/decyloxypropylammonium] bromide (GC6/10-E) were synthesized by two-step reactions. This study analyzes the foam properties, including foamability, foam stability, and foam size distribution, of GC6/10-P and GC6/10-E using the Foamscan method. The influence of surfactant concentration and gas flow rate on the properties of Gemini quaternary ammonium salt foam was also studied. Additionally, the relationship between surfactant structure and foam morphology in aqueous solutions was discussed. The results show that all four types of Gemini quaternary ammonium salt surfactants are low-foaming surfactants. The foam capacity (FC) sequence is as follows: GC10-E > GC10-P > GC6-E > GC6-P. The foamability and foam stability are enhanced with increasing surfactant concentration, which increases the adsorbed quantity of surfactant molecules at the air-water interface. The foam produced by GC6-P/E systems is the most unstable; the foam behaviors show faster Ostwald ripening and drainage process in aqueous system. It seems that 150–200 mL/min is an ideal air intake speed. The presence of hydroxyl in the molecular structure enhances the formation of hydrogen bonding between surfactants and water molecules, leading to greater molecular compactness. The results indicate that the foaming behavior of hydroxyl Gemini quaternary ammonium salts can be correlated with concentration and alkyl chains. Foamscan are proposed to research the foaming and foam stability behavior and provide a useful guide for evaluating the foamability of cationic surfactants-based systems, especially in the development of environmentally friendly foam systems suitable for low-foaming products.

Feasibility test and field application of biofoam spray to directly reduce ammonia emissions from a swine manure slurry pit

Bad-odor gases emitted from swine manure slurry are a global concern because of their detrimental effects on human health and animal welfare. We sprayed odor-removing microbe-loaded surfactant foam (biofoam) directly on the manure slurry surface to suppress NH3 (major odor component in slurry) emissions. Two subsequent experiments were conducted: a feasibility test in a tank and a field manure slurry pit test. The biofoam was sprayed directly onto the slurry once per day. The biofoam sprayed once on the slurry was stable for 20–24 h on the slurry. In the feasibility test tank, 99%–100% NH3 emissions were suppressed for 72 h, and a 61%–89% reduction in NH3 emissions was obtained for 72 h from the field manure slurry pit. The biofoam successfully blocked NH3 emissions. The NH3 reduction efficiency of the biofoam was consistently related to its stability on the surface of the manure slurry. The long-lasting surfactant foam is a good physical suppression cover for reducing NH3 release into the environment. After 72 h, NH3 slowly began to be emitted; nevertheless, the emission was much lower than that of the control. The tiny bubbles that formed after the foam broke still acted as an odor-suppression barrier. Moreover, NH3-reducing microbes loaded onto the surfactant foam degraded NH3 from the manure slurry, and a 34%-63% reduction in NH3 emission was attributed to biological effects after the foam was broken. Overall, NH3 emissions were reduced directly by the biofoam surface covering the manure slurries, the formation of a thin encapsulation layer on the slurry surface, and the activity of spontaneously added microbes. The developed method is a promising odor-reducing technique for swine manure.

Factors Influencing the Rheology of Methane Foam for Gas Mobility Control in High-Temperature, Proppant-Fractured Reservoirs

Gas-enhanced oil recovery (EOR) through huff-n-puff (HnP) is an important method of recovering oil from fracture-stimulated reservoirs. HnP productivity is hampered by fracture channeling, leading to early gas breakthroughs and gas losses. To mitigate these issues, foam-generating surfactants have been developed as a method of reducing injected gas phase mobility and increasing oil recovery. This work investigates foam generation and propagation by a proprietary surfactant blend in high-temperature, high-pressure, high-permeability, and high-shear conditions that simulate the environment of a proppant-packed fracture. Bulk foam tests confirmed the aqueous stability and foaming viability of the surfactant at the proposed conditions. Through several series of floods co-injecting methane gas and the surfactant solution through a proppant pack at residual oil saturation, the effects of several injection parameters on apparent foam viscosity were investigated. The foam exhibited an exceptionally high transition foam quality (>95%) and strong shear-thinning behavior. The foam viscosity also linearly decreased with increasing pressure. Another flood series conducted in an oil-free proppant pack showed that swelling of residual oil had no effect on the apparent foam viscosity and was not the reason for the inversely linear pressure dependency. An additional flood series with nitrogen as the injection gas was completed to see if the hydrophobic attraction between the methane and surfactant tail was responsible for the observed pressure trend, but the trend persisted even with nitrogen. In a previous study, the dependence of foam viscosity on pressure was found to be much weaker with a different foaming surfactant under similar conditions. Thus, a better understanding of this important phenomenon requires additional tests with a focus on the effect of pressure on interfacial surfactant adsorption.

Study on the effects of carbon nanotubes and xanthan gum on the performance of hydrocarbon surfactant foam systems

To improve the foam stability and fire extinguishing efficiency of fluorine-free foam (FFF) extinguishing agents, xanthan gum (XG) and carbon nanotubes (CNTs) were selected as the foam stabilizer agents in this study to investigate their effects on the physical and chemical properties and fire suppression effectiveness of FFF system. The effects of the four factors, namely, α-olefin sulfonic acid Salts (AOS), YT-Y762, XG, and CNTs, on the foam performance were investigated using L9(34) orthogonal design method. Three FFF solutions were selected based on the following four parameters: surface tension, 25% drainage time, foam height, and viscosity. The physicochemical properties, fire extinguishing, and burnback performance of the three FFF solutions were investigated. The results indicated that XG and CNTs have synergistic effects on the FFF solution, and the addition of 0.2 wt% of XG and 0.4 wt% of CNTs increased the 25 % drainage time by 81.40 %. The fire extinguishing performance was effectively improved. The results show the potential application of carbon nanotubes in FFF extinguishing agents.

CO2 soluble surfactants for carbon storage in carbonate saline aquifers with achievable injectivity: Implications from the continuous CO2 injection study

Continuous CO2 injection (CCI) into saline aquifers suffers from low sweep efficiency. While utilizing foam can effectively address this issue, a relatively potent foam design may undesirably reduce the injectivity of CO2. In this study, the potential of CO2-soluble surfactants assisted carbon storage in carbonate saline aquifers was evaluated by core flooding tests and numerical simulations. It is found that foam can be generated at the displacement front during continuous CO2 injection with 0.39 g/L surfactant (CCI + S, fg = 100 %). The CO2 saturation can reach 60 % after 1.0 pore volume of CCI + S, approximately 50 % higher than that of CCI. The maximum pressure gradient is around 1.5 psi/ft at an injection rate of 1.0 ft/d in 162 mD Indiana Limestone for CCI + S. The effects of surfactant concentration, foam quality, and rock permeability were also investigated by core flooding. Moreover, the influence of surfactant partitioning and adsorption on CO2 transport behavior was systematically evaluated by numerical simulation in synthetic and geological models, using modeling parameters that are realistic for field applications. The advantage of injecting surfactant with CO2 is more evident in heterogeneous saline aquifers. Such novel injection strategy provides a promising approach for carbon sequestration in saline aquifers by controlling the mobility of CO2 at the displacement front and simultaneously maintaining acceptable injectivity in the field. The CCI + S process may also impose less risk to the caprock. Expanding the potential CO2 storage sites to heterogeneous saline aquifers could be a game-changer. Our understanding of foam dynamics in porous media could also be advanced.

Silica aerogel nanoparticle-stabilized flue gas foams for simultaneous CO2 sequestration and enhanced heavy oil recovery

With declining conventional reserves, tapping heavy oils generates substantial emissions yet is essential to meet energy demands. This study pioneers an integrated approach using silica aerogels to develop thermally stable flue gas foams for enhanced CO2 sequestration and heavy oil recovery. Microfluidic experiments and molecular dynamics simulations revealed a 5-fold decrease in gas diffusion rates for aerogel-stabilized versus pure surfactant foams at 95 °C due to the ultralow thermal conductivity of the nanoparticle coating layer. The thermally stable nanoengineered foams demonstrated a remarkable 81.23% CO2 trapping efficiency in heterogeneous cores, surpassing conventional flue gas foam. Additionally, three-dimensional simulations in an oil reservoir model showed improved vertical conformance and oil recovery with aerogel-stabilized foam. The exceptional insulating properties redirected heat downward to enhance sweep efficiency. This novel concept transforms flue gas emissions into value-added foams for concurrent environmental and productivity benefits during heavy oil development.

Field application of bio-foam spray to reduce ammonia emission from ammonia-rich swine manure piles

In this study, the first field-scale application of a bio-foam spray (a mixture of microbes and a surfactant) for the reduction of ammonia emitted from manure was investigated on six field swine manure piles. The objective of this study was to evaluate the odor suppression ability of bio-foam and odor degradation ability of odor-degrading bacteria loaded in the surfactant foam after covering manure piles. The size of field manure piles tested in this study ranged from 27 to 300 m3. Bio-foam spraying completely suppressed the release of the major odor component, ammonia (NH3), and odor-degrading bacteria in the bio-foam aided in the degradation of NH3 in field swine manure piles. On average, 85.7–100% of NH3 was reduced after 24–48 h of serial bio-foam spray application on the swine manure surface, while the control showed 25–42%. The reduction efficiency of NH3 by the bio-foam application was affected by the bio-foam spray frequency, ambient temperature, ventilation of the field facility, and upward airflow to the pile. The reduction in surface emission of NH3 also reduced the ambient air concentration of NH3 at the gate of the compost facility. NH3 gas measurements at a depth of 50 cm indicated that NH3-degrading bacteria infiltrated the manure and were active in biodegradation. Finally, the measured effectiveness of bio-foam application as shown by this study indicates that sprinkling bio-foam via specialized rotating sprinklers may be an efficient and uniform method for the delivery of bio-foam to wide field areas within composting facilities.

The effects of wettability and permeability on hydrocarbon foam performance in unconsolidated porous media: An experimental investigation at elevated pressure and temperature conditions

Propped fractures in hydraulically fractured reservoirs function as unconsolidated porous media with permeability orders of magnitude greater than the matrix. This disparity in permeabilities leads to poor conformance control and sweep efficiency. The foam generated inside the fractures can be effective in addressing such challenges. It can reduce the gas mobility and enhancing the fracture-matrix interactions. However, the foam performance is influenced by the wetting conditions and pore space properties of the porous medium. In this work, for the first time, the effect of a complex interplay between permeability and wettability on hydrocarbon foam performance was investigated in unconsolidated porous media. To this end, methane foam experiments were conducted on sandpacks of varying wettability and permeability at high-pressure and high-temperature conditions. Additionally, interdependence between permeability and key foam parameters, including surfactant concentration and foam quality, were probed. Foam performance was evaluated based on the steady-state pressure drops across the medium and the foam’s apparent viscosity. The results showed a non-monotonic dependency of foam strength on the permeability of porous media, irrespective of their wetting conditions. We observed that foamability and foam stability were significantly enhanced at ascending permeability due to enlarged pores and pore-to-throat ratios, leading to reduced gas mobility. However, excessively large pore bodies adversely affected the bubble generation and downgraded the foam performance. Furthermore, foam quality significantly influenced the foam performance at all permeabilities. Distinct foam behavior was observed vis-à-vis variations in foam quality and separated by the low- and high-quality regimes. The results showed a modulated correlation between steady-state foam strength and permeability throughout the low-quality regime; however, no common trends were observed in the high-quality counterpart. Additionally, the transition foam quality was higher in oil-wet media than in water-wet systems. This shift broadened with ascending permeability and can be attributed to the wettability of porous media. Interestingly, variations in surfactant concentration produced similar trends in all wettability cases and displayed insensitivity to permeability. The results indicate that an increase in concentration improved the viscoelastic properties of the aqueous films, improving the foam strength in water- and oil-wet media of all permeabilities.

Performance evaluation of particulate matter removal by surfactant foams

Surfactant foams can be repeatedly formed and ruptured, providing an extensive surface area which can be utilized for the contaminant removal. In order to mitigate the expenses associated with filter maintenance in the filter-equipped device, the particulate matter removal was attempted by the surfactant foam in this study, aiming to assess the feasibility as an alternative technology for improving air quality. Two types of particulate matter (Arizona test dust (ATD) and incense stick) and two types of surfactants (SLS-30 and LAO) were adopted to evaluate the removal efficiency of particulate matter under different surfactant concentrations (0.05, 0.1, and 0.2 wt%) and different flow systems (with and without internal airflow). Overall, ATD were better removed than incense stick due to the larger size which resulted in the greater sedimentation and subsequent contact with foams. Also, SLS-30 showed better removal performance than LAO as the surfactant concentration increased from 0.05 wt% to 0.2 wt%. These findings can be attributed to foam generation properties, in which SLS-30 demonstrated superior foam generation capabilities as the surfactant concentration increased, providing a larger surface area for PM adsorption as well as suppressing the remaining headspace in the chamber. The findings in this study presents the advantageous utilization of foams as an adsorbent for PM as well as a filling material in the limited space, thereby enabling enhanced PM removal capabilities.

Foam in grinding and role of ground mineral in its stability

AbstractSurfactants are usually used as grinding aids. However, surfactant foaming during the grinding process is rarely mentioned in the literature with no clarification of its effect on the grinding process. In this paper, the generation of foam during the grinding of talc and quartz, as two different minerals in their hardness and hydrophobicity, was observed in the presence of sodium dodecyl sulfonate (SDS). The effect of generated foam on the fineness of ground product under different grinding conditions such as solids%, grinding time, and pulp pH was investigated. The results indicated that the foam was formed during the grinding of both minerals. The foam volume depends not only on the presence of surfactant but also on the characteristics of the mineral along with grinding conditions. The foam was intense and more stable particularly at pH 10 and high solid content (i.e., 60% solids) in the case of talc due to its fineness and hydrophobicity that result in bubbles stabilization. Remarkably, there is no foam at acidic pH due to the high ionic strength that leads to bubble instability. Most importantly, the presence of surfactant foams improves the size reduction process by providing more dispersion of particles, as one of the grinding aid mechanisms, due to particle‐particle and particle‐SDS repulsive electrostatic forces.

Superchaotropic ion flotation: A new concept for the extraction and separation of nanometer-sized ions by non-ionic surfactant-based foams

Ion flotation is a separation technology for recovering ions from dilute aqueous solutions. All ion flotation processes known so far make use of ionic foaming agents (surfactants) to selectively extract ions of opposite charge by electrostatic interactions. Recently, it was shown that nanometric-sized ions (nano-ions) with low charge density, such as certain polyoxometalates (POMs), strongly adsorb to neutral hydrated surfaces. In this study, we provide proof-of-concept for a method that we call “superchaotropic ion flotation,” which uses non-ionic surfactant foams to selectively recover and separate superchaotropic POMs from other ions, including non-superchaotropic ions. Specifically, we investigated the extraction of isopolyoxomolybdates, formed by pH and concentration variation of molybdate aqueous solutions, using foams produced with a commercial polyethoxylated surfactant (BrijO10). The speciation of polyoxomolybdates was investigated by Raman spectroscopy and small angle X-ray scattering (SAXS). SAXS has also confirmed the superchaotropic behaviour of the polyoxomolybdates species via the characterization of their strong adsorption on surfactant micelles. The flotation recovering is high and maximal at pH 1, a pH for which Mo36O1128−, an anion with a low charge density, is the predominant molybdate species. It was found that the surfactant has a strong influence on the molybdate speciation. It was also demonstrated that molybdate may be separated from tungstate at pH 2 by superchaotropic ion flotation. In conclusion, we propose a novel ion separation method via non-ionic surfactant aqueous foams and we show that the superchaotropic effect makes it possible to foresee various applications in separation science.

Experimental and computational investigations on foaming properties of anionic-nonionic-zwitterionic surfactants and amino acid compounds to address the liquid loading of natural gas wells

Liquid buildup in gas wells would undoubtedly obstruct the gas production. The use of foaming surfactants to generate foams and remove the loaded liquid is very common. Due to the undesirable conditions (e.g., high condensate cut (ratio of condensate oil volume to total liquid volume) and high salinity, etc.) that often encountered in the wells, different foaming surfactants were often compounded together to unload liquid in gas wells. In this paper, lauramide propyl dimethylamine (C12 Amine), palmitamide propyl dimethylamine (C16 Amine) and cocamidopropyl betaine (CAPB) were synthesized and compounded with L-aspartic acid (Asp) and N-lauroylsarcosine sodium (LSS) to form foaming supramolecular complexes through optimization (with Waring blender method and liquid unloading tests) to quantify their application potentials in foam-based deliquification treatment for gas wells. The C12 Amine-Asp-LSS-CAPB complex (in an optimized mole ratio of 10:4:14:7) exhibited superior condensate tolerance than the C16 Amine-Asp-LSS-CAPB complex (in an optimized mole ratio of 10:4:14:42). The salinity posed a significant influence on the liquid unloading performance (k) and foaming efficiency (ƞ, defined as the ratio of the foam mass to the initial liquid mass) of the C12 Amine-Asp-LSS-CAPB complex, however, the nitrilotriacetic acid trisodium (NTA) can greatly enhance the properties of the C12 Amine-Asp-LSS-CAPB complex against the salinity (up to 6 × 104 mg/L). The temperature (25 °C −90 °C) favored the performances (as indicated by k and ƞ) of the C12 Amine-Asp-LSS-CAPB complex, which achieved k and ƞ values of 85.0% and 100% at 90 °C, respectively. Meanwhile, the synergy observed in the foaming ability, foam stability and liquid unloading performance tests using the C12 Amine-Asp-LSS-CAPB mixture was also proved by the surface tension analysis and the calculations of the supramolecular interactions (interaction energies and electrostatic interactions).

A Comparative Study on CO2-Switchable Foams Stabilized by C22- or C18-Tailed Tertiary Amines

The CO2 aqueous foams stabilized by bioresource-derived ultra-long chain surfactants have demonstrated considerable promising application potential owing to their remarkable longevity. Nevertheless, existing research is still inadequate to establish the relationships among surfactant architecture, environmental factors, and foam properties. Herein, two cases of ultra-long chain tertiary amines with different tail lengths, N-erucamidopropyl-N,N-dimethylamine (UC22AMPM) and N-oleicamidopropyl-N,N-dimethylamine (UC18AMPM), were employed to fabricate CO2 foams. The effect of temperature, pressure and salinity on the properties of two foam systems (i.e., foamability and foam stability) was compared using a high-temperature, high-pressure visualization foam meter. The continuous phase viscosity and liquid content for both samples were characterized using rheometry and FoamScan. The results showed that the increased concentrations or pressure enhanced the properties of both foam samples, but the increased scope for UC22AMPM was more pronounced. By contrast, the foam stability for both cases was impaired with increasing salinity or temperature, but the UC18AMPM sample is more sensitive to temperature and salinity, indicating the salt and temperature resistance of UC18AMPM-CO2 foams is weaker than those of the UC22AMPM counterpart. These differences are associated with the longer hydrophobic chain of UC22AMPM, which imparts a higher viscosity and lower surface tension to foams, resisting the adverse effects of temperature and salinity.