CMC系列高分子表面活性剂与原油超低界面张力形成机理的研究

采用动态激光光散射及环境扫描电镜研究了羧甲基纤维素系列高分子表面活性剂与大庆原油形成超低界面张力的机理.结果表明,CMC系列高分子表面活性剂具有与低分子量表面活性剂相比拟的表/界面活性,其水溶液的表面张力可达2835mN/m,界面张力达到10^-110mN/m.碱的加入可显著降低高分子表面活性剂与原油的界面张力,在适当条件下界面张力达到超低值(10^-3mN/m),可望作为三次采油的驱油剂.等效烷烃模型研究表明,用碱与原油酸性组分的作用来解释碱能使界面张力下降至超低值的传统观点是不完善的,加入碱能使高分子表面活性剂胶束解缔,胶束数量增多,胶束粒径减小,单分子自由链增加,有利于高分子表面活性剂向界面迁移和排布,这是高分子表面活性剂和碱复配体系与原油界面张力下降至超低值的主要原因.     

Experimental Study of the Effect of Strong Alkali on Lowering the Interfacial Tension of Oil/Heavy Alkylbenzene Sulfonates System

Experimental studies were conducted to explore the fundamental mechanisms of alkali to lower the interfacial tension of oil/heavy alkylbenzene sulfonates (HABS) system. Sodium hydroxide was used as the strong alkali chemical to investigate the interfacial tension (IFT) of oil/HABS system. The influences of salt and alkali on the interfacial activity were studied by the measurement of interfacial tension and partition coefficient. Moreover, the alkali/surfactant solutions were measured by dynamic laser scattering. The results showed that compared with the salt, the function of alkali to lower the interfacial tension and improve partition coefficient is more significant. The micelles formed by surfactants could be disaggregated because of adding alkali, so the size of micelles decreases and the number of mono‐surfactants increases, then more surfactant molecules move to the interface of oil/surfactant system and the adsorption of surfactants at oil‐water interfaces increases, which can lead to the decrease of IFT.     

Synthesis and Performance of Novel Sulfonate Gemini Surfactant with Trialkyl Chains

A new type of sulfonate gemini surfactant with three lipophilic alkyl chains (3C₁₀-DS) was synthesized, and the structure of the product was confirmed by using the infrared spectrum and mass spectrum. Its critical micelle concentration (CMC) is 0.41 mmol/L, one order of magnitude lower than those of convectional (single-chain) surfactants, and the minimum surface tension is 27.6 mN/m. The interfacial tension (IFT) between the compound system of 3C₁₀-DS and petroleum sulfonate (PS) and the simulated oil reaches ultra-low levels (10^?3 mN/m), and there exists significant synergistic effect between 3C₁₀-DS and PS. The compound flooding system consisting of polymer and the mixture of 3C₁₀-DS and PS can effectively improve oil recovery for high-medium permeability cores and have a good application prospect in enhancing oil recovery.     

高盐油藏下两性/阴离子表面活性剂协同获得油水超低界面张力

研究了在高盐油藏中, 利用两性/阴离子表面活性剂的协同效应获得油水超低界面张力的方法. 两性表面活性剂十六烷基磺基甜菜碱与高盐矿化水具有很好的相容性, 但在表面活性剂浓度为0.07%-0.39%(质量分数)范围内仅能使油水界面张力达到10^-2 mN·m^-1量级, 加入阴离子表面活性剂十二烷基硫酸钠后则可与原油达到超低界面张力. 通过探讨表面活性剂总浓度、金属离子浓度、复配比例对油水动态界面张力的影响, 发现两性/阴离子表面活性剂混合体系可以在高矿化度、低浓度和0.04%-0.37%的宽浓度范围下获得10^-5 mN·m^-1量级的超低界面张力, 并分析了两性/阴离子表面活性剂间协同获得超低界面张力的机制.     

Interaction between polymer and anionic/nonionic surfactants and its mechanism of enhanced oil recovery

Various experimental methods were used to investigate interaction between polymer and anionic/nonionic surfactants and mechanisms of enhanced oil recovery by anionic/nonionic surfactants in the present paper. The complex surfactant molecules are adsorbed in the mixed micelles or aggregates formed by the hydrophobic association of hydrophobic groups of polymers, making the surfactant molecules at oil-water interface reduce and the value of interfacial tension between oil and water increase. A dense spatial network structure is formed by the interaction between the mixed aggregates and hydrophobic groups of the polymer molecular chains, making the hydrodynamic volume of the aggregates and the viscosity of the polymer solution increase. Because of the formation of the mixed adsorption layer at oil and water interface by synergistic effect, ultra-low interfacial tension (～2.0?×?10^?3 mN/m) can be achieved between the novel surfactant system and the oil samples in this paper. Because of hydrophobic interaction, wettability alteration of oil-wet surface was induced by the adsorption of the surfactant system on the solid surface. Moreover, the studied surfactant system had a certain degree of spontaneous emulsification ability (D50?=?25.04?µm) and was well emulsified with crude oil after the mechanical oscillation (D50?=?4.27?µm).     

Ultra-Low Interfacial Tension Between Heavy Oil and Betaine-Type Amphoteric Surfactants

Betaine surfactants with lipophilic groups of different lengths were synthesized in this research and the dynamic interfacial tension (IFT) between solutions of these surfactants and three kinds of crude oil from Shengli Oilfield are measured. The results indicated that, for Gudao and Gudong heavy oil, cetyl dimethyl hydroxyl sulfobetaine (SBET-16) was the most efficient in lowering the IFT in the case of no alkalis, while for Shengtuo heavy oil, cetyl dimethyl carboxymethyl betaine (CBET-16) was best. SBET-16 with the concentration of 0.003–0.1% and 0.005–0.1% can reduce the oil/water IFT to ultra-low for Gudao and Gudong oil respectively, CBET-16 with the concentration of 0.005–0.1% can lower the oil/water IFT to ultra-low for Shengtuo oil. These results showed that for different oils, an oil displacement agent with high capacity to lower the oil/water interfacial tension may be obtained only by changing the molecular structure of betaine surfactant. This study can be used to guide the design of surfactants for alkaline-free combination flooding.     

Salinity Selection for a Low Salinity Water-Low Salinity Surfactant Process

A laboratory selection of salinity for a low salinity water-low salinity surfactant (LS-LSS) process is presented in this paper with systematical investigation on surfactant phase behavior, interfacial tension (IFT), and dynamic retention in porous media with IOS2024 and isoamyl alcohol (IAA) as surfactant system. The results show that 0.4 wt% IOS2024 with 1 wt% IAA can provide ultra-low IFT of 10^?3 mN/m at around 3000–4000 mg/L total dissolved solids, but at that salinity range the surfactant retention is very high. The search for an optimum surfactant formulation has to consider solution properties and retention in addition to the low IFT. The salinity for a LS-LSS process should thus not be focused on either optimal salinity or ultra-low IFT, but instead the best choice could be a compromise between the properties in question. The three-phase region, where ultra-low IFT are found, is also associated with high retention values. However, we show that as salinity is increased from a two-phase region with oil solubilized in a water continuous microemulsion, there is a region close to the three-phase boundary which has potential. This region does not give ultra-low, but fairly low (10^?2 mN/m in this case) interfacial tensions, and also significantly lower retention.      

Synthesis of Surfactants from Alkali Lignin for Enhanced Oil Recovery

With the cheap and abundant resource of alkali lignin as feedstock, surfactants for enhanced oil recovery were synthesized by amination and alkylation reaction of lignosulfonate. The effects of amination conditions, including the ratio of raw materials, amination reagent, temperature, and reaction time, on nitrogen contents and surface tension of the surfactants were investigated. The results showed that ethylenediamine was more suitable for amination, and the molar ratio of alkali lignin, ethylenediamine, and formaldehyde was 1:2:1.5 at 80°C for 5 hours. The structure of synthesized products was characterized by Fourier transform infrared spectrometry. The HLB value of synthesized product was 10. The interfacial tension between Daqing crude oil and synthetic water could be decreased to 10^?2 mN/m with synthesized surfactant and NaOH at 45°C. Moreover, the effects of molecular weight of surfactants on interfacial tension were also studied. The synthesized surfactant (M_w > 10,000) showed a better interfacial activity on Daqing crude oil.     

阴阳离子表面活性剂体系超低油水界面张力的应用

通过阴阳离子表面活性剂复配,在实际油水体系中获得了超低界面张力.通过在阴离子表面活性剂分子结构中加入乙氧基(EO)链段,以及采用阴阳离子加非离子型表面活性剂的三组分策略,有效解决了混合表面活性剂在水溶液中溶解度问题.进而研究了阳离子表面活性剂结构、非离子表面活性剂结构、三者组分配比、表面活性剂总浓度等因素对油水界面张力的影响,从而在胜利油田多个实际油水体系中获得了较大比例范围和较低浓度区域的油水超低界面张力,部分体系甚至达到了10-4 mN·m-1.由于阴阳离子表面活性剂间强烈的静电吸引作用,相关体系具有很好的抗吸附能力.经过石英砂48 h吸附后,体系仍然具有很好的超低界面张力.     

Synthesis and solution properties of ionic liquid-type polysiloxane bola surfactants

Three novel ionic liquid (IL)-type polysiloxane bola surfactants (ATPS-MA, ATPS-EA, and ATPS-PA) were designed and synthesized using a two-step method. Their chemical structures were characterized by Fourier transform infrared spectroscopy (FTIR) and proton nuclear magnetic resonance (¹H NMR) spectroscopy. Their surface activity and aggregation behavior in aqueous solution were systematically investigated by surface tension measurements, transmission electron microscopy (TEM), and dynamic light scattering (DLS). Surface activity measurement results indicated that the γ_CMC of the three IL-type polysiloxane surfactants are under 25 mN m^?1, and much lower than those of conventional IL hydrocarbon bola surfactants due to the introduction of siloxane group at the end of the hydrophobic chains. TEM and DLS analyses results indicated that the three surfactants can self-assemble into spherical micelles with a range from 50 to 300?nm, indicating potential uses as model systems for biomembranes and vehicles for drug delivery.     

Controlling the melting of kinetically frozen poly(butyl acrylate-b-acrylic acid) micelles via addition of surfactant

We have studied the melting of polymeric amphiphilic micelles induced by small-molecule surfactant and explained the results by experimental determination of the interfacial tension between the core of the micelles and the surfactant solutions. Poly(n-butyl acrylate-b-acrylic acid) (PBA-b-PAA) amphiphilic diblock copolymers form kinetically frozen micelles in aqueous solutions. Strong interactions with surfactants, either neutral or anionic [C12E6, C6E4, sodium dodecyl sulfate (SDS)], were revealed by critical micelle concentration (cmc) shifts in specific electrode and surface tension measurements. Since both polymer and surfactant are either neutral or bear negative charges, the attractive interactions are not due to electrostatic interactions. Light scattering, neutron scattering, and capillary electrophoresis experiments showed important structural changes in mixed PBA-b-PAA/surfactant systems. Kinetically frozen micelles of PBA-b-PAA, that are hardly perturbed by concentration, ionization, ionic strength, and temperature stresses, can be disintegrated by addition of small-molecule surfactants. The interfacial energy of the PBA in surfactant solutions was measured by drop shape analysis with h-PBA homopolymer drops immersed in small-molecule surfactant solutions. The PBA/water interfacial energy gammaPBA/H2O of 20 mN/m induces a high energy cost for the extraction of unimers from micelles so that PBA-b-PAA micelles are kinetically frozen. Small-molecule surfactants can reduce the interfacial energy gammaPBA/solution to 5 mN/m. This induces a shift of the micelle-unimer equilibrium toward unimers and leads, in some cases, to the apparent disintegration of PBA-b-PAA micelles. Before total disintegration, polymer/surfactant mixtures are dispersions of polydisperse mixed micelles. Based on core interfacial energy arguments, the disintegration of kinetically frozen polymeric micelles was interpreted by gradual fractionation of objects (polydisperse dispersion mechanism), whereas the disintegration of polymeric micelles in a thermodynamically stable state was interpreted by an exchange between a population of large polymer-rich micelles and a population of small surfactant-rich micelles (bidisperse dispersion mechanism). Finally, in our system and other systems from the literature, interfacial energy arguments could explain why the disintegration of polymer micelles is either partial or total as a function of the surfactant type and concentration and the hydrophobic block molar mass of the polymer.     

Effect of Polymer on Dynamic Interfacial Tensions of Anionic–nonionic Surfactant Solutions

The dynamic interfacial tensions (IFTs) of enhanced oil recovery (EOR) surfactant/polymer systems against n-decane have been investigated using a spinning drop interfacial tensiometer in this paper. Two anionic–nonionic surfactants with different hydrophilic groups, C₈PO₆EO₃S (6-3) and C₈PO₆EO₆S (6-6), were selected as model surfactants. Partially hydrolyzed polyacrylamide (HPAM) and hydrophobically modified polyacrylamide (HMPAM) were employed. The influences of surfactant concentration, temperature, polymer concentration, and oleic acid in the oil on IFTs have been studied. The experimental results show that anionic–nonionic surfactants can form compact adsorption films and reach ultralow IFT (10^?3 mN/m) under optimum conditions. The addition of polymer has great influence on dynamic IFTs between surfactant solutions and n-decane mainly by the formation of looser mixed films resulting from the penetration of polymer chains into the interface. The compact surfactant film will also be weakened by the competitive adsorption of oleic acid, which results in the increase of IFT. Moreover, the penetration of polymer chains will be further destroyed surfactant/polymer mixed layer and lead to the obvious increase of IFT. On the other hand, polymers show little effect on the IFTs of 6-6 systems than those of 6-3 because of the hindrance of longer EO chain of 6-6 at the interface.     

Synthesis and properties of nonylphenol-substituted dodecyl sulfonate

Nonylphenol-substituted dodecyl sulfonate (C₁₂-NPAS) was synthesized via sulfonation-alkylation-neutralization using 1-dodecene, SO₃, and nonylphenol as raw materials. The properties such as surface tension, interfacial tension (IFT), wettability, foam properties, and salinity tolerance of C₁₂-NPAS were systematically investigated. The results show that the critical micelle concentration (CMC) of C₁₂-NPAS was 0.22?mmol?·?L^?1 and the surface tension at the CMC (γ_CMC) of C₁₂-NPAS was 29.4 mN/m. When compared with the traditional surfactants sodium dodecyl benzene sulfonate (SDBS), sodium dodecyl sulfate (SDS), and linear alkylbenzene sulfonate (LAS), the surface properties of C₁₂-NPAS were found to be superior. The IFT between Daqing crude oil and a weak-base alkaline/surfactant/polymer (ASP) oil flooding system containing 0.1?wt% of C₁₂-NPAS can reach an ultralow level of 2.79?×?10^?3 mN/m, which was lower than that found for the traditional surfactant heavy alkylbenzene sulfonate (HABS). The salinity and hardness tolerance of C₁₂-NPAS were much stronger than those found for conventional surfactants, petroleum sulfonate, and LAS. C₁₂-NPAS also shows improved wetting performance, foamability, and foam stability.     

Interfacial Properties,Wettability Alteration and Emulsification Properties of an Organic Alkali–Surface Active Ionic Liquid System: Implications for Enhanced Oil Recovery

Combinatory flooding techniques evolved over the years to mitigate various limitations associated with unitary flooding techniques and to enhance their performance as well. This study investigates the potential of a combination of 1-hexadecyl-3-methyl imidazolium bromide (C₁₆mimBr) and monoethanolamine (ETA) as an alkali–surfactant (AS) formulation for enhanced oil recovery. The study is conducted comparative to a conventional combination of cetyltrimethylammonium bromide (CTAB) and sodium metaborate (NaBO₂). The study confirmed that C₁₆mimBr and CTAB have similar aggregation behaviors and surface activities. The ETA–C₁₆mimBr system proved to be compatible with brine containing an appreciable concentration of divalent cations. Studies on interfacial properties showed that the ETA–C₁₆mimBr system exhibited an improved IFT reduction capability better than the NaBO₂–CTAB system, attaining an ultra-low IFT of 7.6 × 10⁻³ mN/m. The IFT reduction performance of the ETA–C₁₆mimBr system was improved in the presence of salt, attaining an ultra-low IFT of 2.3 × 10⁻³ mN/m. The system also maintained an ultra-low IFT even in high salinity conditions of 15 wt% NaCl concentration. Synergism was evident for the ETA–C₁₆mimBr system also in altering the carbonate rock surface, while the wetting power of CTAB was not improved by the addition of NaBO₂. Both the ETA–C₁₆mimBr and NaBO₂–CTAB systems proved to form stable emulsions even at elevated temperatures. This study, therefore, reveals that a combination of surface-active ionic liquid and organic alkali has excellent potential in enhancing the oil recovery in carbonate reservoirs at high salinity, high-temperature conditions in carbonate formations.     

Surface activity and thermodynamic properties of water‐soluble polyester surfactants based on 1,3‐dicarboxymethoxybenzene used for enhanced oil recovery

The surface activity and thermodynamic properties for eight low molecular weight nonionic co‐polyester (PE) surfactants have been investigated. Surface and interfacial tensions (IFT) of surfactants in aqueous solutions were measured using the spinning drop technique. From these measurements, the critical micelle concentration (CMC), the surface pressure at CMC (Y_CMC), the maximum surface concentration (Γ_max), the minimum area/molecule at the aqueous solution/air interface (A_min), the effectiveness of surface tension reduction (Π_CMC), the alkane carbon number (n_min) and the IFT at n_min (Y_min) were determined. The thermodynamic parameters of micellization (ΔG_mic, ΔH_mic and ΔS_mic) and of adsorption (ΔG_ad, ΔH_ad and ΔS_ad) for these polymeric surfactants were also calculated. Structural effects on micellization and adsorption are discussed in terms of these parameters. The results show that the ΔG_ad values were more negative than ΔG_mic values for these compounds, so that they favored adsorption before the micellization process. They exhibited IFT in the order of 10⁻³ to 10⁻⁴ mN/m against the thin alkane carbon number range 6–9. This range seemed to be prefered for enhanced oil recovery. Copyright © 2000 John Wiley & Sons, Ltd.     

Dynamic Interfacial Tension Behavior of Water/Oil Systems Containing In situ-Formed Surfactants

Time-dependent interfacial tension (IFT) has been investigated for an interfacially reactive immiscible system composed of model-acidified oil and alkaline water. The acidified oil was composed of either lauric acid or linoleic acid dissolved in n-dodecane. Drop volume tensiometry was employed to measure the interfacial tension between the two phases. In the case of lauric acid, the IFT value was found to decrease sharply with increasing alkali concentration, even at low drop formation times. In the case of linoleic acid, the IFT decrease with the drop formation time was more gradual, especially at low alkali concentration. The rate of formation of the interfacial area was also found to be dependent on alkali concentration.     

Study on the Interfacial Tensions Between Oils and Alkylbenzene Sulfonate Gemini Surfactant Solutions

Interfacial tensions (IFT) of five alkylbenzene sulfonate Gemini surfactants Ia, Ib, Ic, Id, and Ie at different oils/water systems were measured by a spinning drop interfacial tensiometer. And critical micelle concentration (CMC), the interfacial tension at CMC (γ_CMC), maximum interfacial excess concentration (Γ _max) and the surface area per molecule (A_min) were calculated. The results indicated that the CMC values determined with interfacial tension method were lower than those determined with surface tension method. And γ_CMC for Ie is larger than that for Ia, Ib, Ic, and Id. In addition, the effects of temperature and hydrophobic chains on dynamic IFT were also studied. With the increment of temperature, dynamic IFT is easier to reach a stable value. However, with the increment of hydrophobic chains, dynamic IFT is more difficult to reach a stable value. Each Gemini surfactant produces a minimum IFT when measured against a different n-alkane.     

Research and application of ultralow interfacial tension oil displacement agent

An ultralow interfacial tension (IFT) oil displacement agent, which was a surfactant combinational system (HCS) with good salt and heat resistance, was synthesized using amphoteric betaine (AMS)/anionic sulfonate (AKS)/nonionic alkyl amide (NIS). The interface tensiometer was used to test the IFT. The results showed that the oil–water IFT could be as low as 10^?4 mN/m when the salinity is 10,000～50,000?mg/L, the concentration is 1～5?g/L, and the temperature is 40～80°C. The surfactant system has good emulsification stability. The displacement simulation experiments demonstrated that the increment of the recovery ratio can be up to 14.1%. The surfactant system could meet the demands of site operation.     

CORRELATION BETWEEN INTERFACIAL TENSIONS AND MICELLAR STRUCTURES

It is shown that results of surface and interfacial tension measurements can be used to predict the type of micelles and of liquid crystalline phases which are formed in binary and ternary surfactant solutions. In particular it is possible to predict the position of l.c. cubic phases in ternary systems consisting of surfactant, hydrocarbon and water. Data to demonstrate the conclusions were obtained on the surfactants Alkyltrimethylammoniumbromides, Alkyldimethylaminoxides and Alkyldimethylphosphinoxides. It was found that the interfacial tension of a dilute micellar solution against a reference hydrocarbon is a most sensitive and indicative parameter for the prediction of the different structures. Large changes of the interfacial tension were observed for the three systems having the same hydrocarbon chainlength. The value of the interfacial tension directly reflects also the amount of hydrocarbon which can be solubilized in the micellar solution. Interfacial tensions larger than 1mN/m are indicative of globular micelles while interfacial tensions between 0.1 and 1 mN/m indicate the formation of rods. Values below 0.1 mN/m indicate disclike micelles or lamellar phases.

The interfacial tension depends somewhat on the kind of hydrocarbon which is used for the measurements. It is observed that for several surfactant solutions the interfacial tension passes through a shallow minimum when the chainlength of the hydrocarbon is increased from six to sixteen.     

Foam Flooding with Ultra-Low Interfacial Tension to Enhance Heavy Oil Recovery

Severe viscous fingering during water flooding of heavy oil leaves a large amount of oil untouched in the reservoir. Improving sweep efficiency is vital for increasing heavy oil recovery. Previous researches have proved that foam flooding can increase the sweep efficiency and oil recovery. The polymers could make the foam more stable and have better plugging capacity, but the interfacial tension (IFT) of oil and water increase which could decrease the displacement efficiency of the heavy oil. In view of the deficiency of conventional foam flooding, it is necessary to research the ultra-low interfacial tension foam which could improve macro-swept volume and micro-displacement efficiency in heavy oil reservoir. In this paper a novel foam agent is developed by the combination of surfactant and additives to lower the IFT of oil and water. The operating parameters including foam injections modes and gas liquid ratio were investigated by core flooding experiments. Field test performance shows that oil production per day increased from 85.6 to 125.7 t, water cut declined from 92.1 to 83.6% after 3 months injection. This study provides a novel method to improve heavy oil recovery with an ultra-low interfacial tension foam flooding system.