Foam Generation Research Articles

Saponin foam for soil remediation: On the use of polymer or solid particles to enhance foam resistance against oil

Foams can be used to remediate aquifer pollution due to industrial leaks. However, when in contact with oily pollutants, foams may collapse and thus have a very limited life-time. A suitable formulation of biodegradable foam that resists oil contact is therefore needed. Hence, the ability of xanthan polymer and silica colloidal particles to stabilise foam against oil was investigated. Their performance in terms of stabilisation was evaluated via foam generation experiments in columns of porous medium, conducted with and without oil. The results show that the addition of xanthan polymer led to an increase in the viscosity of the solution, which thwarted the formation of foam. It did not improve the resistance of foam to oil, but increased altogether the resistance factor up to more than twice the original value. Concerning silica particles, it was demonstrated that they both noticeably increased resistance factor and moderately stabilised foam against oil by 20% at optimum concentration. As such, this study presents a new way to reinforce foam against oil for soil remediation issues.

Experimental study of high-temperature CO2 foam flooding after hot-water injection in developing heavy oil reservoirs

Hot water flooding is one of the main strategies employed in the recovery of heavy oil. However, the low viscosity of the injected hot water readily generates the formation of water channels in oil bearing formations with high permeability, resulting in relatively low oil recovery. This study addresses this issue by experimentally investigating the application of a CO2 foam injection process as a secondary strategy after hot water injection. Six surfactants were evaluated for foam generation at temperatures in the range of 57–200 °C in a series of screening tests, including static foam tests, thermal stability testing, and resistance factor evaluation. The optimum surfactant was accordingly selected for application in the CO2 foam injection process. The addition of 0.04 wt% anionic polyacrylamide (HPAM) as a stabilizer in the selected surfactant produced a more stable foam appropriate for use at a temperature of 80 °C or less. Oil displacement experiments were conducted using both a high permeability sand pack and a low permeability sand pack simultaneously to investigate water channel creation during hot water injection and the channel blockage resulting from the injected foam along with the corresponding oil recovery enhancement. The experimental results indicate that hot water in the hot water injection process flows readily through the high permeability sand pack and reduces the oil viscosity, which results in an increased degree of water channeling of the high-permeability sand pack. The high-temperature CO2 foam generated under optimum conditions using the selected surfactant effectively blocks the water channeling created during the preceding hot water injection process and significantly increases the oil displacement efficiencies of both the low- and high-permeability sand packs. The results of this study demonstrate that the secondary injection of CO2 foam following hot water injection represents a promising heavy oil recovery strategy for developing heavy oil reservoirs.

ЗАЛЕЖНІСТЬ ВЛАСТИВОСТЕЙ КОМПРЕСІЙНОЇ ПІНИ ВІД РОБОЧИХ ПАРАМЕТРІВ ПРОЦЕСУ ГЕНЕРУВАННЯ ПІНИ

Для системи пожежогасіння компресійною піною наведено результати дослідження залежності властивостей компресійної піни, а саме: стійкості, кратності, адгезії, витрат піноутворювача та води, тривалості гасіння від робочих параметрів процесу генерування піни, таких як тип та концентрація піноутворювача, робочий тиск у системі генерування піни.Наведено результати випробування з визначення тривалості гасіння компресійною піною низької кратності модельного вогнища пожежі 55 В і показника вогнегасної здатності за класом пожежі. У разі гасіння компресійною піною низької кратності та їх порівняння з відповідними показниками ефективності повітряно-механічної піни середньої кратності, одержаної з використанням ежекційних стволів-генераторів піни.

Modeling Steady-State Foam Flow: Hysteresis and Backward Front Movement

Foaming gaseous injectants is an attractive option because of the much lower gas mobility achieved in porous media. This paper reports an experimental and numerical investigation to improve our understanding of aqueous foam flow in heterogeneous sandstone. Our experimental program reveals two interesting behaviors: hysteresis in the steady-state pressure gradient and movement of a foam front opposite the direction of flow. Steady-state pressure gradient measurements across a sandstone core demonstrate the absence of a critical velocity requirement for foam generation, support the possibility of foam propagation away from the injection well, and exhibit hysteresis in the pressure gradient upon decreasing the injection gas velocity. Quasi-steady pressure drop profiles show that the pressure gradient increases against the direction of flow in what we coin the ”backward front movement”. This paper models experimental observations of steady-state pressure-drop hysteresis as well as quasi-steady backward front movement. Specifically, a steady-state population balance model that is based on pore-scale observations is developed. The model is verified against experimental data to confirm the steady-state predictions of the pressure, the flowing bubble density, and the flowing foam fraction (Tang and Kovscek, Transport in Porous Media 2006, 65, 287–307; Chen et al. SPE J. 2010, 15, 171–183). The model is then used to predict the experimental behavior. The flowing foam fraction (i.e., the fraction of the gas saturation that flows) is a key parameter in interpreting both hysteresis and backward propagation of the pressure gradient. Our findings highlight the importance of the flowing foam fraction to predicting various foam behavior.

Evaluation of performance of foam produced with different methodologies for use in foam concrete production

For the production of foam concrete which finds applications in many areas, generally as a function of its relatively lightweight, the use of stable and quality foam is the key requirement. However, the literature available on the influence of characteristics of foaming agent and foam on the properties of foam concrete are rather limited. Hence a more systematic research is needed in this direction. The present work focuses on the relative performance evaluation of foam (initial foam density, foam stability, viscosity of surfactant solution and bubble size) using a typical synthetic surfactant and additive using two different foam production methodologies namely stirrer and foam generator. Comparative studies on foam production methods indicated that foam produced based on compressed air method (foam generator) is of better quality with lesser liquid fraction and drainage compared to that of foam produced with stirrer. Also studies have proved that there is a strong relationship between viscosity of surfactant solution, initial foam density, foam stability and bubble microstructure.

Experimental study of heat transfer enhancement in liquid piston compressor using aqueous foam

Efficiency of gas compression can be significantly improved by achieving isothermal compression. A high heat transfer rate in the compression chamber is desired to achieve the isothermal compression process. A large surface area and a high heat transfer coefficient of aqueous foam can be used to achieve a significantly high heat transfer rate in the compression chamber. In this study, a novel heat transfer enhancement technique using aqueous foam is investigated in a compressor for achieving near-isothermal compression. Experiments are performed with the use of aqueous foam generated inside a liquid piston compressor. The volume of aqueous foam in the compression chamber, the air flow rate for foam generation, and various foam generator designs are considered in this parametric investigation. It is observed that the use of aqueous foam in the compression chamber is highly effective in reducing air temperature during the compression process. A higher volume of aqueous foam in the compression chamber leads to a significant increment in isothermal efficiency, however, with higher variability. The higher variability in efficiency is due to the higher cyclic variation of the temperature profiles during compression. A compression chamber completely filled with aqueous foam shows a 4–8% improvement in the efficiency for a compression ratio of 2.5. Moreover, several foam generator designs were tested to identify if there is any dependency of cyclic variability on foam generator design parameters. The results show some promise on optimizing the design to reduce the variability. Overall, the heat transfer enhancement using aqueous foam is effective in achieving an isothermal efficiency up to 92% compared to 86% for the no-foam case in a liquid piston compressor.

How Cellulose Nanofibrils Affect Bulk, Surface, and Foam Properties of Anionic Surfactant Solutions.

We study the generation and decay of aqueous foams stabilized by sodium dodecyl sulfate (SDS) in the presence of unmodified cellulose nanofibrils (CNF). Together with the rheology of aqueous suspensions containing CNF and SDS, the interfacial/colloidal interactions are determined by quartz crystal microgravimetry with dissipation monitoring, surface plasmon resonance, and isothermal titration calorimetry. The results are used to explain the properties of the air/water interface (interfacial activity and dilatational moduli determined from oscillating air bubbles) and of the bulk (steady-state flow, oscillatory shear, and capillary thinning). These properties are finally correlated to the foamability and to the foam stability. The latter was studied as a function of time by monitoring the foam volume, the liquid fraction, and the bubble size distribution. The shear-thinning effect of CNF is found to facilitate foam formation at SDS concentrations above the critical micelle concentration (cSDS ≥ cmc). Compared with foams stabilized by pure SDS, the presence of CNF enhances the viscosity and elasticity of the continuous phase as well as of the air/water interface. The CNF-containing foams have higher liquid fractions, larger initial bubble sizes, and better stability. Due to charge screening effects caused by sodium counter ions and depletion attraction caused by SDS micelles, especially at high SDS concentrations, CNF forms aggregates in the Plateau borders and nodes of the foam, thus slowing down liquid drainage and bubble growth and improving foam stability. Overall, our findings advance the understanding of the role of CNF in foam generation and stabilization.

Development of the highly boosted capillary porous foam generator for gas (steam) mechanical foam

A highly boosted capillary porous foam generator for gas (steam) mechanical foam is developed. It contains the inlet and outlet nozzles, nozzles for supply of the foam generating solution and foam discharge, package of the foam generating meshes with increased sizes and sprayer. In order to increase capacity and improve the foam characteristics, the generator is equipped with a capillary patch and forming channel. The capillary patch is located at the external surface of perforated pipe that supplies the foam generating solution, and the forming channel is installed outside of the capillary patch with feeder. Additionally, the foam generator has control plates located at both sides of the feeding device, where the plates at both sides pass into a spring guiding viewfinder, also the packet of foamed grids with increasing size in the direction of gas flow is made with dimensions 0.4x0.55.

Compressive strength prediction of lightweight foamed concrete with various densities

A research has been undertaken to study the compressive strength of foamed concrete with various concrete density. This paper reports experimental investigation on lightweight foamed concrete of 300, 600, 800 and 1000 kg/m3 densities and correlates compressive strength and density for further strength prediction. A total of 72 foamed concrete cubes with various densities and water cement ratio were prepared and tested for compressive strength at the concrete age of 7 and 28 days. Inverted slump and flow table spread value were obtained based on the test method stated in ASTM C1611. The foams were produced by using foam generator by mixing them with cement mortar (Ordinary Portland Cement, OPC and dry sand of size 850μm). The experimental results showed the highest compressive strength was recorded as 2 MPa for the density of 1000kg/m3 and water cement ratio of 0.6. The results revealed that consistency of the foamed concrete is in the range of 0.97 to 1.03, whereas stability index is in the range of 0.98 to 1.19 which showed the bubbles in the foamed concrete were stable during casting and curing process. A prediction model with exponential equations were proposed for foamed concrete compression strength with different water-cement ratio and it can be preliminary used to predict the foamed concrete strength.

Nanoparticle/polymer-enhanced alpha olefin sulfonate solution for foam generation in the presence of oil phase at high temperature conditions

Foam flooding can improve oil recovery performance through reducing gas mobility in subsurface porous media. However, foam in porous media is thermodynamically unstable, especially in reservoir conditions where it is in contact with hydrocarbons (oil phase). In this study, the use of silica (SiO2) and rice husk ask (RHA) nanoparticles with xanthan gum (XG) and acacia gum (AG) polymers, is proposed to improve the foam stability at high temperature and high salinity conditions in the presence of oil phase. Moreover, it was highlighted that the potential use of RHA, extracted from waste materials, and natural acacia gum can substitute previously proposed synthesized nanoparticles and polymers as foam additives for immiscible displacement in subsurface porous media.The results show that the addition of polymers do not change the surface tension at high temperatures, and its combination with nanoparticles can increase the viscosity of surfactant remarkably. It was found that an increase in the stability of CO2-foam can be achieved with increasing nanoparticles and polymer concentrations to optimum concentrations. Furthermore, foam stability increases with decreasing the nanoparticles sizes and increasing the molecular weight of the polymer.In order to understand the performance of the optimum foam composition at high temperature and salinity conditions, the foam was brought into contact with a reservoir oil. It was shown that the CO2-foam stability in the presence of oil, could be enhanced by using nanoparticles and polymers, compared to the CO2-foam system with no additives. The reason for such improvement is due to the presence of nanoparticles and polymers in lamellae that break the oil into the emulsion droplets system that can flow easily through the lamellae without draining the entire surfactant solution from them.

CT coreflood study of foam flow for enhanced oil recovery: The effect of oil type and saturation

We present a CT coreflood study of foam, both pre-generated and generated in-situ, displacing oil, as a function of oil type and saturation. Foam generation and propagation are reflected through sectional pressure measurements. Dual-energy CT imaging monitors in-time phase saturations. With an oil less harmful to foam (hexadecane), injection with and without pre-generation of foam exhibits similarities: propagation of a foam bank through a core and later refinement of foam texture. In contrast, with an oil destabilizing to foam (with 20 wt% oleic acid in the hexadecane), pre-generation of foam behaves very differently from co-injection, suggesting very-different effects on foam generation and propagation. Without pre-generation, strong-foam generation is very difficult even at residual oil saturation (about 0.1); generation finally starts from the outlet (likely a result of the capillary-end effect). This strong-foam state propagates upstream very slowly. Pre-generated foam shows two stages of propagation, both from the inlet to outlet. First, weak foam displaces most of the oil, followed by a propagation of stronger foam at lower oil saturation. This dependence on injection method with harmful oil is not represented in currently applied foam models, which need further improvements for reliable prediction of foam for enhanced oil recovery.

Internal Olefin Sulfonate Foam Coreflooding in Low-Permeable Limestone at Varying Salinity

Effects of salinity, total flow rate, and gas flow rate on the foam generation using internal olefin sulfonate (IOS) surfactant were investigated. The compatibility tests performed at 1–11% NaCl at...

A pore-scale study on improving CTAB foam stability in heavy crude oil−water system using TiO2 nanoparticles

The main challenge of foam injection for enhanced oil recovery (EOR) is foam stability at harsh reservoir conditions. With regard to this matter, this research aims to investigate the effect of TiO2 nanoparticles (NPs) in improving the stability of foam bubbles in porous media. The conductivity of hexadecyltrimethylammonium bromide (CTAB) solutions was measured to determine critical micelle concentration (CMC). Thereafter, TiO2 NPs were added into the foam solution and pH, contact angle, and interfacial tension (IFT) in the presence and absence of CTAB were measured. The stability of foam bubbles was evaluated through bulk foam tests and absorbance measurements. Finally, different nanofluids (at the concentrations of 0.00, 0.01, 0.03, 0.06, and 0.10 wt%), nano-CTAB solutions (at the concentrations of 0.00, 0.01, 0.03, 0.06, and 0.1 wt% NPs at the CMC of CTAB) and foams (at the concentrations of 0.00, 0.01, 0.03, 0.06, and 0.1 wt% NPs and at the CMC of CTAB) were injected into a heavy oil saturated heterogeneous porous medium. The results of the conductivity measurements showed that the highest adsorption of CTAB molecules onto the NPs surfaces occurs at 0.03 wt% NPs and 0.03 wt% CTAB. The results of micro- and macroscopic images from bulk foam tests revealed improved foam stability for this nano-CTAB foam. Moreover, contact angle and IFT results showed further improvement in interfacial properties for the mixture of NPs and CTAB solutions. Ultimately, in terms of oil recovery, the highest oil recovery factor (54%) was observed upon injection of foam with 0.03 wt% TiO2 NPs and 0.03 wt% CTAB, compared to the 22% recovery factor of DW injection. The visualization experiments showed that 32% enhancement in the recovery factor was mainly due to oil production from dead−end pores. This was because of different functions of NPs including stabilization of foam bubbles, wettability alteration, and improved foam generation mechanisms.

The coupled dynamics of foam generation and pipe flow

Foam generation in porous media and foam flow through pipes have been studied extensively to date as uncoupled processes. The coupled dynamics of foam generation and pipe flow, however, are comparatively understudied, despite their importance to industrial applications. We consider an experimental system that generates foam by flowing air and surfactant solution through a bead pack, after which the foam flows through a pipe to a downstream pressure chamber. We systematically vary the foam flow rate, bead diameter, bead pack length, pipe length, and chamber pressure. We measure the corresponding impact on flow pressures, densities, velocities, composition, and textures throughout the system, including direct measurements of bubble diameter distributions. We show that with the proper non-dimensionalization, the generator and pipe flows collapse to surprisingly simple friction-factor relationships. We also show that the mean foam bubble diameter exiting the bead pack decreases with increasing flow rate, up to a minimum value set by the pore length-scale K, where K is the bead pack permeability. We also explore the impact of foam texture and composition on the effective foam viscosities within the pipe. Finally, we show that foam properties evolve within the pipe, such that the pipe and bead pack play equally important roles in determining outlet foam properties.

A novel acidizing technology in carbonate reservoir: In-Situ formation of CO2 foamed acid and its self-diversion

The serious fingering and nonuniform injectivity profile of acid liquid result from the features of heterogeneity in most carbonate reservoir, leading to a poor effect on the acidizing process. In the present contribution, for the first time, we report a novel diversion acidizing strategy that uses acid-rock reaction between the acidizing fluid itself and carbonate core to produce CO2 at supercritical state. Under the action of a mixture of foaming agent and stabilizer contained in this working fluid, a CO2 foamed acid fluid is in-situ formed in the acidizing layer, which would play a diverting role in carbonate matrix acidizing operations. Experiments on in-situ formation of CO2 microfoams (emulsions) were performed utilizing a visible acid-rock reaction simulation device and a self-made high pressure and temperature foam generator. A series of divided-flow experiments were undertaken by the core displacement setup.Results based on these experiments indicate that with 0.5% SDBS as a foaming agent and 0.15% CMC as a stabilizing agent, the supercritical CO2 microfoams (emulsions) could be created in-situ in the process of acidizing through the carbonate reservoirs. The foamed acid has the accumulating and plugging effects, with divided-flow selectivity not only in the parallel cores of oil saturation and water saturation, but also in the parallel cores of different permeability. This foamed acid fluid could provide better diversion acidizing operations for heterogeneous carbonate formation. Finally, the mechanism of this novel diversion acidizing technology was uncovered in detail. It is suggested that the whole working process is actually an interface effect in the dynamic system of gas/liquid/solid multiphase fluid. Such findings are potentially important for a better understanding on the mechanisms of in-situ formation of CO2 foamed acid and its self-diversion. Looking out to the future, our report attempts to provide a new and efficient technology for the improvement of acid stimulation in the carbonate reservoirs.

Ultralow-Interfacial-Tension Foam-Injection Strategy in High-Temperature Ultrahigh-Salinity Fractured Oil-Wet Carbonate Reservoirs

Summary Oil recovery in many carbonate reservoirs is challenging because of unfavorable conditions, such as oil–wet surface wettability, high reservoir heterogeneity, and high brine salinity. We present the feasibility and injection–strategy investigation of ultralow–interfacial–tension (IFT) foam in a high–temperature (greater than 80°C), ultrahigh–formation–salinity [greater than 23% total dissolved solids (TDS)] fractured oil–wet carbonate reservoir. Because a salinity gradient is generated between injection seawater (SW) (4.2% TDS) and formation brine (FB) (23% TDS), a frontal–dilution map was created to simulate frontal–displacement processes and thereafter it was used to optimize surfactant formulations. IFT measurements and bulk–foam tests were also conducted to study the salinity–gradient effect on the performance of ultralow–IFT foam. Ultralow–IFT foam–injection strategies were investigated through a series of coreflood experiments in both homogeneous and fractured oil–wet core systems with initial oil/brine two–phase saturation. The representative fractured system included a well–defined fracture by splitting the core sample lengthwise. A controllable initial oil/brine saturation in the matrix can be achieved by closing the fracture with a rubber sheet at high confining pressure. The surfactant formulation achieved ultralow IFT (magnitude of 10−2 to 10−3 mN/m) with the crude oil at the displacement front and good foamability at underoptimal conditions. Both ultralow–IFT and foamability properties were found to be sensitive to the salinity gradient. Ultralow–IFT foam flooding achieved more than 50% incremental oil recovery compared with waterflooding in fractured oil–wet systems because of the selective diversion of ultralow–IFT foam. This effect resulted in a crossflow near the foam front, with surfactant solution (or weak foam) primarily diverted from the fracture into the matrix before the foam front, and oil/high–salinity brine flowing back to the fracture ahead of the front. The crossflow of oil/high–salinity brine from the matrix to the fracture was found to create challenges for foam propagation in the fractured system by forming Winsor II conditions near the foam front and hence killing the existing foam. It is important to note that Winsor II conditions should be avoided in the ultralow–IFT foam process to ensure good foam propagation and high oil–recovery efficiency. Results in this work contributed to demonstrating the technical feasibility of ultralow–IFT foam in high–temperature, ultrahigh–salinity fractured oil–wet carbonate reservoirs and investigated the injection strategy to enhance the low–IFT foam performance. The ultralow–IFT formulation helped to mobilize the residual oil for better displacement efficiency and reduce the unfavorable capillary entry pressure for better sweep efficiency. The selective diversion of foam makes it a good candidate for a mobility–control agent in a fractured system for better sweep efficiency.

Numerical Simulation of Air Entrainment Performance of a Foam Generator Used for Dust Control in Coal Mines

Mine dust is one of the most serious environmental hazards in the coal mining process. This paper introduces a numerical simulation of a novel foam generator used for dust control in coal mines. The amount of foam generated by this device significantly depends on the amount of air entrainment. Therefore, a computational fluid dynamics (CFD) method was used to study three influencing factors, namely, throat-nozzle distance, mixing throat length, and the contraction angle of the suction chamber. The predicted values by the CFD simulation proved to be in good agreement with the experimental data. The results revealed that the air entrainment reached its maximum when the ratio of throat-nozzle distance to mixing throat length was 2/3. The optimum values of the throat ratio (its length to diameter) and the contraction angle of the suction chamber were obtained at 20 and 5°, respectively. This research provides essential guidance in the geometric parameter design of the self-suction type foam generator, which has the advantage of negating the need for compressed-air pipelines and having high reliability, compared to traditional foam generators.

Electroplating for chromium removal from tannery wastewater

The performance of electroplating in the removal of chromium ions from crude tannery wastewater and from a synthetic wastewater solution was investigated. Brazil is a major producer of leather, and such industries generate large environmental impacts. A novel batch reactor setup was developed for tannery wastewater treatment, employing graphite and aluminum as anode and cathode, respectively. Crude wastewater from a tannery was characterized and presented an acidic pH, elevated biochemical oxygen demand and chemical oxygen demand, and a total chromium concentration of 544 mg/L, a value that is one thousand times higher than permitted by local legislation. Electroplating was able to remove 90.0% of chromium content from a synthetic trivalent chromium solution. Moreover, 96.5% of total chromium content was removed when electroplating was applied in untreated tannery wastewater. Additionally, antifoam addition inhibited foam generation during the electroplating process without interfering in chromium removal. The results showed that the electroplating technique is a viable wastewater treatment alternative and/or a complement for tannery industries that use chromium as a tanning agent.

Role of Counterions and Nature of Spacer on Foaming Properties of Novel Polyoxyethylene Cationic Gemini Surfactants

Application of foam in various upstream operations, such as in enhanced oil recovery, has gained significant attention in recent years. A good foaming agent should generate a stable foam, must be thermally stable (>90 °C, typical reservoir temperature), must have a high tolerance to salinity, and should have low adsorption on the reservoir rock. In view of this, four thermally stable and salt-tolerant polyoxyethylene cationic gemini surfactants were synthesized with different spacers (mono phenyl and biphenyl) and different counterions (Br− and Cl−). Foaming properties were evaluated using initial foam generation, foam volume stability at a given time, bubble count, and average foam bubble radius. The effect of counterions and nature of spacers, with and without the presence of salts, on foaming properties was evaluated. It was found that number of phenyl rings (mono phenyl and biphenyl) had no significant effect on foamability and foam stability in the presence or absence of salts. However, the effect of counterions was prominent in deionized water. In deionized water, foam generated by gemini surfactants with bromide as a counterion was more stable compared to the foam generated using the surfactant containing chloride as the counterion. In saline solution, the type of counterion had no effect on the foamability or foam stability of the foam generated using synthesized cationic gemini surfactants. The foam volume stability decreased by the addition of salts; however, a further increase in salt concentration enhanced the foam volume stability. The synthesized surfactants showed good thermal stability, salt tolerance, and foaming properties and can be an attractive choice for upstream applications.

Classification of foam and foaming products for EPB mechanized tunnelling based on half-life time

During tunnel excavation with Tunnel Boring Machines (TBMs) and earth pressure balance (EPB) technology, conditioning agents are commonly used to modify the physical and mechanical properties of soils so that they are appropriate for the application of the front-face support pressure during excavation. The consistency of the conditioned soil must be stable during the time necessary to advance and install the lining. Hence, a stability analysis of the injected foams is an important aspect. To assess the stability of a foam a classification is proposed based on the results of a standard foam generation procedure and on half-life tests using products from the main suppliers. A further classification of the foaming agents used according to their ability to produce a stable foam in terms of Foam Expansion Ratio is also proposed.