Lauryl alcohol and amine oxide as foam stabilizers in the presence of hardness and oily soil

The effects of two potential foam boosters, n-dodecanol (or lauryl alcohol: LA) and tetradecyldimethylamine oxide (C₁₄DMAO), were investigated for two situations in which foam made from a 0.01 wt% solution of a common alkylethoxy sulfate surfactant was highly unstable in the presence of oil drops consisting of an n-hexadecane/oleic acid mixture. In one case in which dissolved CaCl₂ was present at alkaline pH, insoluble calcium oleate particles formed in situ and facilitated foam breakage. In the other, a much higher concentration of calcium was present at neutral pH, and drops of a microemulsion phase formed but no calcium oleate. In both cases, 0.005 wt% LA reduced the entry coefficient, E, of the oil to the air-water surface sufficiently to prevent drop entry and stabilized the foam. In contrast, 0.005 wt% C₁₄DMAO caused smaller reductions in E and was ineffective as a foam booster. LA was more effective because it was able to form a more compact monolayer with the surfactant than C₁₄DMAO at the air-water surface, which led to lower surface tensions and hence lower values of E.     

Stabilization of natural gas foams using different surfactants at high pressure and high temperature conditions

Natural gas foam can be used for mobility control and channel blocking during natural gas injection for enhanced oil recovery, in which stable foams need to be used at high reservoir temperature, high pressure and high water salinity conditions in field applications. In this study, the performance of methane (CH₄) foams stabilized by different types of surfactants was tested using a high pressure and high temperature foam meter for surfactant screening and selection, including anionic surfactant (sodium dodecyl sulfate), non-anionic surfactant (alkyl polyglycoside), zwitterionic surfactant (dodecyl dimethyl betaine) and cationic surfactant (dodecyl trimethyl ammonium chloride), and the results show that CH₄-SDS foam has much better performance than that of the other three surfactants. The influences of gas types (CH₄, N₂, and CO₂), surfactant concentration, temperature (up to 110°C), pressure (up to 12.0 MPa), and the presence of polymers as foam stabilizer on foam performance was also evaluated using SDS surfactant. The experimental results show that the stability of CH₄ foam is better than that of CO₂ foam, while N₂ foam is the most stable, and CO₂ foam has the largest foam volume, which can be attributed to the strong interactions between CO₂ molecules with H₂O. The foaming ability and foam stability increase with the increase of the SDS concentration up to 1.0 wt% (0.035 mol/L), but a further increase of the surfactant concentration has a negative effect. The high temperature can greatly reduce the stability of CH₄-SDS foam, while the foaming ability and foam stability can be significantly enhanced at high pressure. The addition of a small amount of polyacrylamide as a foam stabilizer can significantly increase the viscosity of the bulk solution and improve the foam stability, and the higher the molecular weight of the polymer, the higher viscosity of the foam liquid film, the better foam performance.     

Solution Properties and Displacement Characteristics of in situ CO2 Foam System for Enhanced Oil Recovery

Carbon dioxide (CO₂) foam flooding has been shown to enhance oil recovery. However, large-scale adoption has been restricted by issues with transportation of CO₂ and equipment corrosion. In situ CO₂ foam generation can possibly overcome these issues. In this article, a CO₂ sustained-release system was first optimized for the CO₂ production rate and production efficiency. Then, the dissolution capacity and plug-removing ability of the sustained-release system were evaluated. Visual experiment and parallel sand pack flooding tests were conducted to verify the formation, propagation of in situ CO₂ foam, and the feasibility of this technique. The results indicated that the sustained-release system had benign ability to lower injection pressure and improve injectability. Moreover, in situ CO₂ foam flooding could obtain high oil recovery due to favorable mobility control ability, interfacial tension reduction capacity, and heterogeneity improvement. All the experiments demonstrated that the in situ CO₂ foam technique has great potential for enhanced oil recovery in the Bohai oilfield.     

Investigation on Foam Self‐Generation Using In Situ Carbon Dioxide (CO2) for Enhancing Oil Recovery

In situ carbon dioxide (CO₂) foam flooding has proved to be economically feasible in the oil field, but its self‐generation behavior in the bulk scale/porous media is far from understood. In this study, the optimum in situ CO₂‐foaming agent was first screened, and then in situ foam was investigated in the bulk. In situ foam flooding was conducted to evaluate the displacement characteristics and enhanced oil recovery of this system. The results showed that the foaming agent comprising 0.5% sodium dodecyl sulfonate (SDS) + 0.5% lauramido propyl hydroxyl sultaine (LHSB) gave the best foam properties and that the in situ CO₂ foam with a slow releasing rate is effective both in bulk scale and in porous media, allowing a considerable enhancement of oil recovery in sand packs with different permeabilities.     

Mechanistic simulation of continuous gas injection period during surfactant-alternating-gas (SAG) processes using foam catastrophe theory

The use of foam for mobility control is a promising means to improve sweep efficiency in subsurface applications such as improved/enhanced oil recovery and aquifer remediation. Foam can be introduced into geological formations by injecting gas and surfactant solutions simultaneously or alternatively. Alternating gas and surfactant solutions, which is often referred to as surfactant-alternating-gas (SAG) processes, is known to effectively create fine-textured strong foams in situ by repeating drainage and imbibition processes. Recent studies show that foam rheology in porous media can be characterized by foam catastrophe theory which exhibits three foam states (weak-foam, strong-foam, and intermediate states) and two strong-foam regimes (high-quality and low-quality regimes).Using both mechanistic foam simulation technique and fractional flow analysis which are consistent with foam catastrophe theory, this study aims to understand the fundamentals of dynamic foam displacement during gas injection in SAG processes. The results revealed some important findings: (1) the complicated mechanistic foam fractional flow curves (f_w vs. S_w) with both positive and negative slopes require a new way to solve the problem analytically rather than the typical method of constructing a tangent line from the initial condition; (2) none of the conventional mechanistic foam simulation and fractional flow analysis can fully capture sharply changing dynamic foam behavior at the leading edge of gas bank, which can be overcome by the pressure-modification procedure suggested in this study; (3) four foam model parameters (?p_o, n, C_g/C_c, and C_f) can be determined systematically by using an S-shaped foam catastrophe curve, a two flow-regime map, and a coreflood experiment showing the onset of foam generation; and (4) at given input data set of foam simulation parameters, the inlet effect which explains a delay in strong-foam propagation near the core face is scaled by the system length, and therefore the change in system length requires a new set of individual lamella creation and coalescence parameters (C_g and C_c).     

Effect of oil viscosity on recovery processes in relation to foam flooding

Laboratory experiments were conducted to determine the effect of oil viscosity on the oil-recovery efficiency in porous media. The pure surfactants (i.e., sodium dodecyl sulfate and various alkyl alcohols) were selected to correlate the molecular and surface properties of foaming solutions with viscosity, and the recovery of oil. Oil-displacement efficiency was measured by water, surfactant-solution and foam-flooding processes, which included 2 types of foams (i.e., air foam and steam foam). A significant increase in heavy-oil recovery was observed by steam foam flooding compared with that by air foam flooding, whereas for light oils, the steam foam and air foam produced about the same oil recovery. An attempt was made to correlate the chain-length compatibility with the surface properties of the foaming agents and oil-recovery efficiency in porous media. For mixed foaming systems (C₁₂ SO₄ Na + C_n H_2n+1 OH), a minimum in surface tension, a maximum in surface viscosity, a minimum in bubble size and a maximum in oil recovery were observed when both components of the foaming system had the same chain length. These results were explained on the basis of thermal motions (i.e., vibrational, rotational and oscillational) and the molecular packing of surfactants at the gas-liquid interface. The effects of chain-length compatibility and the surface properties of mixed surfactants are relevant to the design of surfactant formulations for oil recovery under given reservoir conditions.     

Synthesis of an Alkyl Polyoxyethylene Ether Sulfonate Surfactant and Its Application in Surfactant Flooding

Surfactant flooding as a potential enhanced oil‐recovery technology in a high‐temperature and high‐salinity oil reservoir after water flooding has attracted extensive attention. In this study, the synthesis of an alkyl alcohol polyoxyethylene ether sulfonate surfactant (C₁₂EO₇S) with dodecyl alcohol polyoxyethylene ether and sodium 2‐chloroethanesulfonate monohydrate, and its adaptability in surfactant flooding were investigated. The fundamental parameters of C₁₂EO₇S were obtained via surface tension measurement. And the ability to reduce oil–water interfacial tension (IFT), wettability alteration, emulsification, and adsorption was determined. The results illustrated that IFT could be reduced to 10^?3 mN m^?1 at high temperature and high salinity without additional additives, and C₁₂EO₇S exhibited benign wettability alternate ability, and emulsifying ability. Furthermore, the oil‐displacement experiments showed that C₁₂EO₇S solution could remarkably enhance oil recovery by 16.19% without adding any additives.     

Stability improvement of CO2 foam for enhanced oil‐recovery applications using polyelectrolytes and polyelectrolyte complex nanoparticles

CO₂ foam for enhanced oil‐recovery applications has been traditionally used in order to address mobility‐control problems that occur during CO₂ flooding. However, the supercritical CO₂ foam generated by surfactant has a few shortcomings, such as loss of surfactant to the formation due to adsorption and lack of a stable front in the presence of crude oil. These problems arise because surfactants dynamically leave and enter the foam interface. We discuss the addition of polyelectrolytes and polyelectrolyte complex nanoparticles (PECNP) to the surfactant solution to stabilize the interface using electrostatic forces to generate stronger and longer‐lasting foams. An optimized ratio and pH of the polyelectrolytes was used to generate the nanoparticles. Thereafter we studied the interaction of the polyelectrolyte–surfactant CO₂ foam and the polyelectrolyte complex nanoparticle–surfactant CO₂ foam with crude oil in a high‐pressure, high‐temperature static view cell. The nanoparticle–surfactant CO₂ foam system was found to be more durable in the presence of crude oil. Understanding the rheology of the foam becomes crucial in determining the effect of shear on the viscosity of the foam. A high‐pressure, high‐temperature rheometer setup was used to shear the CO₂ foam for the three different systems, and the viscosity was measured with time. It was found that the viscosity of the CO₂ foams generated by these new systems of polyelectrolytes was slightly better than the surfactant‐generated CO₂ foams. Core‐flood experiments were conducted in the absence and presence of crude oil to understand the foam mobility and the oil recovered. The core‐flood experiments in the presence of crude oil show promising results for the CO₂ foams generated by nanoparticle–surfactant and polyelectrolyte–surfactant systems. This paper also reviews the extent of damage, if any, that could be caused by the injection of nanoparticles. It was observed that the PECNP–surfactant system produced 58.33% of the residual oil, while the surfactant system itself produced 47.6% of the residual oil in place. Most importantly, the PECNP system produced 9.1% of the oil left after the core was flooded with the surfactant foam system. This proves that the PECNP system was able to extract more oil from the core when the surfactant foam system was already injected. © 2016 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2017 , 134, 44491.     

The liquid-gas mass transfer coefficient in open channel flow is correlated to the turbulent kinetic energy at the interface

Mass transfer coefficients at the gas-liquid interface were investigated for different flow configuration systems, a stirred tank reactor and a gravity pipe. Computational fluid dynamics (CFD) simulations were performed for all tested experimental conditions. Since a poorly soluble gas (oxygen) was used, the overall mass transfer coefficient was clearly correlated to the hydrodynamic conditions in the liquid phase. However, a generic correlation between averaged interfacial liquid velocity and mass transfer coefficients was not found for both geometries. Finally, the averaged turbulent kinetic energy (TKE) at the interface is the most relevant parameter that was correlated to the mass transfer coefficient for both systems. The same relationship between oxygen mass transfer coefficient K _L,O2 and TKE () can be applied for the two geometries investigated.     

Synergistic Effects between Anionic and Sulfobetaine Surfactants for Stabilization of Foams Tolerant to Crude Oil in Foam Flooding

In foam flooding, foams stabilized by conventional surfactants are usually unstable in contacting with crude oil, which behaves as a strong defoaming agent. In this article, synergistic effects between different surfactants were utilized to improve foam stability against crude oil. Targeted to reservoir conditions of Daqing crude oil field, China (45 °C, salinity of 6778 mg L⁻¹, pH = 8–9), foams stabilized by typical anionic surfactants fatty alcohol polyoxyethylene ether sulfate (AES) and sodium dodecyl sulfate (SDS) show low composite foam index (200–500 L s) and low oil tolerance index (0.1–0.2). However, the foam stability can be significantly improved by mixing the anionic surfactant with a sulfobetaine surfactant, which behaves as a foam stabilizer increasing the half-life of foams, and those with longer alkyl chain behave better. As an example, by mixing AES and SDS with hexadecyl dimethyl hydroxypropyl sulfobetaine (C₁₆HSB) at a molar fraction of 0.2 (referring to total surfactant, not including water), the maximum composite foaming index and oil tolerance index can be increased to 3000/5000 L s and 1.0/4.0, respectively, at a total concentration between 3 and 5 mM. The attractive interaction between the different surfactants in a mixed monolayer as reflected by the negative β^s parameter is responsible for the enhancement of the foam stabilization, which resulted in lower interfacial tensions and therefore negative enter (E), spreading (S), and bridging (B) coefficients of the oil. The oil is then emulsified as tiny droplets dispersed in lamellae, giving very stable pseudoemulsion films inhibiting rupture of the bubble films. This made it possible to utilize typical conventional anionic surfactants as foaming agents in foam flooding.     

Experimental Study of In-Situ CO<Subscript>2</Subscript> Foam Technique and Application in Yangsanmu Oilfield

The Yangsanmu oilfield of Dagang is a typical heavy oil reservoir. After the maximum primary production (waterflooding), more than half of the original oil is still retained in the formation. Therefore, the implementation of an enhanced oil recovery (EOR) process to further raise the production scheme is inevitable. In this work, a novel in-situ CO₂ foam technique which can be used as a potential EOR technique in this oilfield was studied. A screening of gas producers, foam stabilizers and foaming agents was followed by the study of the properties of the in-situ CO₂ foam systems through static experiments. Core-flooding experiments and field application were also conducted to evaluate the feasibility of this technique. The results indicated that the in-situ CO₂ foam system can improve both the sweep and displacement efficiencies, due to the capacity of this system in reducing oil viscosity and interfacial tension, respectively. The EOR performance of the in-situ CO₂ foam system is better than the single-agent and even binary system (surfactant-polymer) flooding. The filed data demonstrated that the in-situ CO₂ technique can significantly promote oil production and control water cuts. These results are believed to be beneficial in making EOR strategies for similar reservoirs.     

Surfactant properties of purified polyglycerol monolaurates

A series of purified polyglycerol monolaurates (PGML), such as di-, tri-, tetra-, and pentaglycerol monolaurates, were synthesized, and their surfactant properties in aqueous solutions were examined. The surfactant properties of PGML were compared with those of n-dodecyl polyoxyethylene monoethers (C₁₂EO_n) to examine the function of the hydrophilic part of these compounds. The critical micelle concentration (CMC) values and the surface tension at CMC of PGML and C₁₂EO_n increased linearly with an increase in the number of glycerol and oxyethylene units, respectively; the slope of the increase was greater for PGML than C₁₂EO_n. The minimum surface area per molecule of PGML was smaller than that of C₁₂EO_n at the air/aqueous solution interface. The initial foam heights of the surfactants at the CMC increased with an increase in the number of glycerol or oxyethylene units, and the foam heights of PGML were consistently higher and more stable than those of C₁₂EO_n. Detergency depended on a reduction in interfacial tension. Triglycerol monolaurate showed the lowest interfacial tension and the highest detergency among all the surfactants tested. Overall, the PGML showed better performance in all the surfactant properties tested than C₁₂EO_n. It is noteworthy that the surfactant properties of PGML having few glycerol units (di- to tetraglycerol monolaurates) are on par with those of C₁₂EO_n having many oxyethylene units (hexa- and octaoxyethylene). These results suggest that PGML having a secondary hydroxyl group on every glycerol unit of the hydrophilic part could be more hydrophilic than C₁₂EO_n; this characteristic feature guaranteed the superior surfactant properties of PGML.     

Recovery of valeric acid using green solvents

In this work, extraction of valeric acid (VA) using tri-n-butyl phosphate (TBP) as a reactive extractant was carried out. To reduce the toxic effects of the conventional diluents on microorganisms, non-toxic and green edible sunflower and soybean oils were tried as the diluents. The high values of the distribution coefficient and extraction efficiency advocated to use them in the bio-refinery industries. Moreover, it shows intensification of the recovery of VA using reactive extraction process. Sunflower oil appeared to be a better diluent than soybean oil. The complexation reaction stoichiometry (m and n) and equilibrium complexation reaction constant $K_{E\left(m:n\right)}$ were estimated by using the differential evolution technique. In spite of the loading ratio being less than 0.5, the estimated m/n was found to be more than 1.0. The higher values of $K_{E\left(m:n\right)}$ occurred due to the 9higher stability of the VA-TBP complex in sunflower oil than in soybean oil. The stoichiometry of VA decreased with increasing TBP concentration. The complex concentration, ${\left[{\left(\mathit{HA}\right)}_m{S}_n\right]}_{\mathrm{org}}$, was found to be higher for soybean oil. It increased with temperature and initial VA concentration but remained invariant with TBP concentration. Due to the decreasing trend of $K_{E\left(m:n\right)}$ with temperature, the complexation reaction became exothermic. The enthalpy changes due to mass transfer stipulated easier mixing of the phases in sunflower oil than in soybean oil.     

Comparative Investigation of Dynamic Foam Behavior of Air–Water and CO2–Water Systems

The purpose of this study was to understand and compare the dynamic foam behavior of the surfactant Tween‐20 in air–water and CO₂–water systems. The foam height in the CO₂–water system was less than that in the air–water system, but the foam stability was better in the CO₂–water system. The effect of temperature on axial dye displacement and foam bubble size was studied, where the foam generation ability of the surfactant was directly proportional to the temperature, while the foaminess was inversely proportional. The observed highest foam volume for the air–water system was 3922 ± 181 cm³ and for the CO₂–water system 3195 ± 181 cm³ at 5.0 g L^–1 of surfactant at air flow rate of 1 liter per minute (LPM) at 52 °C. The half‐life for the air–water and the CO₂–water system was 110 and 40 s, respectively, at 5.0 g L^–1 of surfactant at the air flow rate of 1 LPM and 28 °C. In wet foam, the liquid holdup range for the air–water system was 0.38–0.52% and for the CO₂–water system 0.51–0.72% in the concentration range 1.0–5.0 g L^–1 at 1 LPM gas flow rate.     

Recovery of Surfactant from an Aqueous Solution Using Continuous Multistage Foam Fractionation: Mixed Surfactant System

A continuous multistage foam fractionation column with bubble caps was used for surfactant recovery from mixed surfactant solutions containing polyethylene glycol tert-octylphenyl (OPEO₁₀) and cetylpyridinium chloride (CPC) and the effects of air flow rate, foam height, and feed flow rate were investigated under a steady state of conditions. For the mixed surfactant system, the effect of synergism in the surfactant adsorption density was found. For separation efficiency, the total residual factor remained unchanged with an increasing feed molar fraction of OPEO₁₀ (α), suggesting that the addition of OPEO₁₀ does not increase the total separation efficiency. The residual factor of CPC increased with an increasing molar fraction of OPEO₁₀ (α), while the residual factor of OPEO₁₀ was lower for the mixed surfactant systems. A competitive removal was found in that the OPEO₁₀ can compete with CPC for the bubble surface. The total separation factors and enrichment ratio of mixed surfactant systems were in-between the two single surfactant systems at a long foam residence time and, in contrast, showed antagonism at short foam residence. This is due to the difference in liquid entrainment in foam at long and short foam residence times.     

Effects of compositional variations on CO2 foam under miscible conditions

Foam can mitigate the associated problems with the gas injection by reducing the mobility of the injected gas. The presence of an immiscible oleic phase can adversely affect the foam stability. Nevertheless, under miscible conditions gas and oil mix in different proportions forming a phase with a varying composition at the proximity of the displacement front. Therefore, it is important to understand how the compositional variations of the front affect the foam behavior. In this study through several core‐flood experiments under miscible condition, three different regimes were identified based on the effects of the mixed‐phase composition on CO₂ foam‐flow behavior: In Regime 1 the apparent viscosity of the in‐situ fluid was the highest and increased with increasing x_CO2. In Regime 2 the apparent viscosity increased with decreasing x_CO2. In Regime 3 the apparent viscosity of the fluid remained relatively low and insensitive to the value of x_CO2. © 2017 American Institute of Chemical Engineers AIChE J, 64: 758–764, 2018     

A modified fuzzy clustering framework for catalyst activity monitoring in the selective catalytic reduction system

The catalyst activity monitoring in the selective catalytic reduction (SCR) system is of great importance for safety and economic operation in the power plant. To address the problem, a framework based on clustering considering time delay has been proposed. A compound parameter, $q$, is put forward in this paper as a strategy to remove the influences from gas volume (power output), inlet NO_x concentration, and outlet NO_x concentration to the ammonia amount. A modified entropy-based fuzzy clustering (EFC) method is proposed by a threshold varying model and then tested for its efficiency by four datasets from the University of California, Irvine (UCI) machine learning repository. With the maximum mutual information entropy coefficient (MIC) method for detecting time delay and the modified EFC method, process data from three working levels are handled for automatically obtained clustering centres. The proposed activity value, $\mu$, is then calculated based on 1440 process data before and after the catalyst replacement shown in boxplot figures. The results of the framework are analyzed to be in accordance with the real working conditions, with $\mu$ values and fluctuation ranges starting to fall near first from the 721st sample in the 24th box.     

Removal of motor oil by continuous multistage froth flotation: Effect of operational parameters

A continuous multistage froth flotation column was employed to remove motor oil from water at a low concentration (500 mg/L) using an extended surfactant – branched alcohol propoxylate sulphate sodium salt (C_14-15–8PO–SO₄–Na) – as a frother. The highest separation efficiency (97% motor oil removal with the enrichment ratio of 16 for motor oil) was obtained at a foam height of 60 cm, an air flow rate of 40 L/min, a feed flow rate of 60 mL/min, a surfactant concentration of 0.3% (w/v), and an NaCl concentration of 1.5% (w/v). The process performance increased with increasing tray number but beyond 4 trays, the system could only offer lower concentrations of motor oil and surfactant in the effluent.     

Polyurethane foams from soyoil‐based polyols

The focus of this work was to synthesize bio‐based polyurethane (PU) foams from soybean oil (SO). Different polyols from SO were produced as follows: soybean oil monoglyceride (SOMG), hydroxylated soybean oil (HSO), and soybean oil methanol polyol (SOMP). The SOMG was a mixture of 90.1% of monoglyceride, 1.3% of diglyceride, and 8.6% of glycerol. The effect of various variables (polyol reactivity, water content curing temperature, type of catalyst, isocyanate, and surfactant) on the foam structure and properties were analyzed. SOMG had the highest reactivity because it was the only polyol‐containing primary hydroxyl (? OH) groups in addition to a secondary ? OH group. PU foams made with SOMG and synthetic polyol contained small uniform cells, whereas the other SO polyols produced foams with a mixture of larger and less uniform cells. The type of isocyanate also had an influence on the morphology, especially on the type of cells produced. The foam structure was found to be affected by the water and catalyst content, which controlled the foam density and the cure rate of the PU polymer. We observed that the glass transition (T_g) increased with the OH value and the type of diisocyanate. Also, we found that the degree of solvent swelling (DS) decreased as T_g increased with crosslink density. These results are consistent with the Twinkling Fractal Theory of T_g. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2009     

泡沫复合驱配方ZS-23的研究

泡沫驱作为一项重要的三次采油技术,在降低气油比、增加原油产量、提高波及效率等诸多方面具有很大的发展潜力。对ZS系列泡沫复合驱配方进行了探索性研究,使用Waring Blender法对泡沫复合驱配方的发泡能力和稳定性进行了检测,通过实验筛选出发泡性能好、稳定性强的泡沫复合驱配方。在矿化度NaCl>5 000 mg/L、CaCl2>3 000 mg/L条件下,表现最为优异的配方为ZS-23,在常温(20℃)时,发泡体积达到880 mL,析液半衰期5.3 h以上,加盐后发泡体积达到820 mL,析液半衰期3.5 h以上,均远远好于一般常见的发泡剂。