Interfacial Tensions of Ethoxylated Fatty Acid Methyl Ester Solutions Against Crude Oil

The dynamic interfacial tension (IFT) of ethoxylated fatty acid methyl ester solutions against n‐alkanes, kerosene, and diluted heavy oil have been investigated by spinning drop interfacial tensiometry. The influences of ethylene oxide (EO) groups and alkyl chain length on IFT were investigated. The experiment results show that the water solubility decreases with an increase in alkyl chain length or a decrease in EO groups. The ability to lower the interfacial tension against hydrocarbons improves with both increasing alkyl chain length and EO group at the best hydrophilic‐lipophilic balance, which can be attributed to the enhancement of the interfacial hydrophobic interactions and the rearrangement of interfacial surfactant molecules. The mixed adsorption of surfactant molecules and surface‐active components may reduce IFT to a lower value. C₁₈=E₃ shows the best synergism with surface‐active components. However, the IFT values against pure crude oil are obviously higher than those against hydrocarbons, which may be caused by the nature of heavy oil.     

Study on the Adaptability of Alkanolamide (LDEA) Lowering Oil/Water Interfacial Tension to Different Crude Oils

In order to investigate the high interfacial activity and fair oil phase adaptability of alkanolamide, “1:1” type lauric acid diethanolamide impurities (LDEA) were synthesized and purified by the column chromatography method to obtain dodecanoic acid diethanolamide (C₁₂DEA), ester mixture, etc. The exact structures of these compounds were further confirmed by IR, gas chromatogrph with mass spectroscopy (GC–MS), and NMR. The influence of each component on the interfacial tension of oil/water (IFT) was studied by systematic quantitative analysis. The results showed that (i) the strength of each system to reduce oil/water IFT is C₁₂DEA /DEA ≈ LDEA > C₁₂DEA/DEA/ESTER > C₁₂DEA/NaOH > C₁₂DEA > C₁₂DEA/ESTER > DEA. This indicates that LDEA contributes to the reduction of the oil/water IFT and the enhanced adaptability of crude oil in this order: DEA > > ESTER; (ii) when the IFT of the LDEA/DEA system reached an ultralow value, the minimum content of DEA in the system was 1%, and the maximum ester content was less than 5% when the LDEA/DEA/ESTER system reached the ultralow IFT; (iii) the possible mechanism of effect of LDEA components on the IFT and oil phase adaptability was proposed as the synergistic process among the hydrogen bonding, alkali effect, and interface self-assembly of molecules in the interfacial layer. The contribution of these three factors were hydrogen bonding > alkali effect > interface self-assembly.     

Fatty and Resinic Acids Extraction from Crude Tall Oil

Abstract

The separation of fatty and resinic acidic fractions from crude tall-oil soap solutions with n-heptane by the technique of dissociation extraction is discussed. The theory of the overall process is supported by a systematic study developed to cover the high selectivity demonstrated in the differential solubility and the aptness between fatty and diterpenic acids to both liquids phases. To study the main factors affecting those liquid-liquid extraction systems and the amphiphilic behavior of such molecules involved, sodium salts aqueous solutions of crude tall oil and synthetic mixtures as molecular acidic models were used.     

Superior enhancement of imbibition recovery by novel surfactant mixtures with a large hydrophobic group combined with nanosilica

Low interfacial tension (IFT) drainage and imbibition are effective methods for improving oil recovery from reservoirs that have low levels of oil or are tight (i.e., exhibit low oil permeability). It is critical to prepare a high efficient imbibition formula. In this work, a novel 2,4,6-tris(1-phenylethyl)phenoxy polyoxyethylene ether hydroxypropyl sodium sulfonate (TPHS) surfactant was synthesized and evaluated for imbibition. Its structure was confirmed by Fourier transform infrared spectroscopy and the interfacial tension (IFT) of the crude oil/0.07% TPHS solution was 0.276 mN/m. When 0.1 wt% TPHS was mixed with 0.2 wt% alpha olefin sulfonate (AOS), the IFT was lowered to 6 × 10⁻² mN/m. The synergy between nanoparticles (NPs) and TPHS/AOS mixed surfactant was studied by IFT, contact angle on sandstone substrates, zeta potential, and spreading dynamics through microscopic methods. The results show that the surfactant likely adsorbs to the NP surface and that NP addition can help the surfactant desorb crude oil from the glass surface. With the addition of 0.05 wt% SiO₂ NPs (SNPs), the imbibition oil recovery rate increased dramatically from 0.32%/h to 0.87%/h. The spontaneous imbibition recovery increased by 4.47% for original oil in place (OOIP). Compared to flooding by TPHS/AOS surfactant solutions, the oil recovery of forced imbibition in the sand-pack increased by 12.7% OOIP, and the water breakthrough time was delayed by 0.13 pore volumes (PV) when 0.05% SNPs were added. This paper paves the way for enhanced oil recovery in low-permeability sandstone reservoirs using novel TPHS/AOS surfactants and SNPs.     

The effect of mixed surfactants on enhancing oil recovery

Micelles composed of mixed surfactants with different structures (mixed micelles) are of great theoretical and industrial interest. This work pertains tomaximizing interfacial tension (IFT) reduction via surfactant pairs. In this respect, four types of fatty acid amides based on lauric, myristic, palmitic, and stearic acids were blended with dodecyl benzene sulfonic acid at a molar ratio of 4∶1 and designated as A₁, A₂, A₃, and A₄, respectively. The IFT was measured for each blend at different concentrations using Badri crude oil. The most potent formula (A₄) was evaluated for using in enhanced oil recovery (EOR). The IFT was tested in the presence of different electrolyte concentrations with different crude oils at different temperatures. Finally several runs were devoted to study the displacement of Badri crude oil by A₄ surfactant solution using different slug sizes of 10, 20, and 40% of pore volume (PV). The study reveled that Badri crude oil gave ultra-low IFT at lowest surfactant concentration and 0.5% of NaCl. The recovery factor at a slug size of 20% PV was 83% of original oil in place compared with 59% in case of conventional water flood.     

AN IMPROVED MODEL FOR THE INTERFACIAL BEHAVIOR OF CAUSTIC/CRUDE OIL SYSTEMS

The effects of crude oil acid number and brine concentration on the interfacial behavior of caustic/crude oil systems were investigated. The effect of increased brine concentration was generally to increase the minimum interfacial tension (IFT) while low IFT values were retained for longer periods of time. Varying the crude oil acid number caused the shape of the IFT versus time curve to change, while the minimum IFT remained constant. These combined results imply that Lagmuir and not Henry soption (adsorption/desorption) kinetics were operative

A phenomenological surface phase model for the IFT behavior of caustic/crude oil systems is proposed which incorporates Langmuir kinetics. The model takes into account interfacial activities of the acidic components in the crude and the detailed chemistry of the oil phase, the water phase, and the interface. To allow for realistic comparison of model results with interfacial tensiometer data, drastic interfacial volume changes which accompany the transient interfacial tensions in the system are taken into account.     

十八烷基己基甲基羧基甜菜碱的合成及性能

以硬脂酸和己酸为原料合成了不对称双长链烷基羧基甜菜碱——十八烷基己基甲基羧基甜菜碱(C18+6B),测定了C18+6B的表面活性,并与总碳原子数相等的对称型双十二烷基甲基羧基甜菜碱(diC12B)进行比较,以了解表面活性剂分子结构对性能的影响。结果表明,C18+6B的表面活性与diC12B基本相当,但水溶性远好于diC12B。作为无碱驱油用表面活性剂,C18+6B对大庆原油来说HLB值略偏高,45 ℃ 下单独使用能将大庆原油/地层水界面张力降至10-2mN/m数量级,在大庆油砂上的饱和吸附量比diC12B低30%。C18+6B单独能将C7~C9正构烷烃/大庆地层水界面张力降至10-3mN/m数量级,而通过与亲油性更强的diC12B以及亲水性甜菜碱复配后,能将大庆原油/地层水界面张力降至10-3mN/m数量级,并能显著改善配方的水溶性。     

十八烷基己基甲基羧基甜菜碱的合成及性能

以硬脂酸和己酸为原料合成了不对称双长链烷基羧基甜菜碱——十八烷基己基甲基羧基甜菜碱(C18+6B),测定了C18+6B的表面活性,并与总碳原子数相等的对称型双十二烷基甲基羧基甜菜碱(di C12B)进行比较,以了解表面活性剂分子结构对性能的影响。结果表明,C18+6B的表面活性与di C12B基本相当,但水溶性远好于di C12B。作为无碱驱油用表面活性剂,C18+6B对大庆原油来说HLB值略偏高,45℃下单独使用能将大庆原油/地层水界面张力降至10-2m N/m数量级,在大庆油砂上的饱和吸附量比di C12B低30%。C18+6B单独能将C7~C9正构烷烃/大庆地层水界面张力降至10-3m N/m数量级,而通过与亲油性更强的di C12B以及亲水性甜菜碱复配后,能将大庆原油/地层水界面张力降至10-3m N/m数量级,并能显著改善配方的水溶性。     

Interfacial properties of cationic and anionic Gemini surfactant mixtures

The possibility and the prospect of cationic/anionic (“catanionic”) surfactant mixtures based on sulfonate Gemini surfactant (SGS) and bisquaternary ammonium salt (BQAS) in the field of enhanced oil recovery was investigated. The critical micelle concentration (CMC) of SGS/BQAS surfactant mixtures was 5.0 × 10⁻⁶ mol/L, 1–2 orders of magnitude lower than neat BQAS or SGS. A solution of either neat SGS or BQAS, could not reach an ultra-low interfacial tension (IFT); but 1:1 mol/mol mixtures of SGS/BQAS reduced the IFT to 1.0 × 10⁻³ mN/m at 100 mg/L. For the studied surfactant concentrations, all mixtures exhibited the lowest IFT when the molar fraction of SGS among the surfactant equaled 0.5, indicating optimal conditions for interfacial activity. The IFT between the 1:1 mol/mol SGS/BQAS mixtures and crude oil decreased and then increased with the NaCl and CaCl₂ concentrations. When the total surfactant concentration was above 50 mg/L, the IFT of SGS/BQAS mixtures was below 0.01 mN/m at the studied NaCl concentrations. Adding inorganic salt reduced the charges of hydrophilic head groups, thereby making the interfacial arrangement more compact. At the NaCl concentration was above 40,000 mg/L, surfactant molecules moved from the liquid–liquid interface to the oil phase, thus resulting in low interfacial activity. In addition, inorganic salts decreased the attractive interactions of the SGS/BQAS micelles that form in water, decreasing the apparent hydrodynamic radius (D_{H, app}) of surfactant aggregates. When the total concentration of surfactants was above 50 mg/L, the IFT between the SGS/BQAS mixtures and crude oil decreased first and then increased with time. At different surfactant concentrations, the IFT of the SGS/BQAS mixtures attained the lowest values at different times. A high surfactant concentration helped surfactant molecules diffuse from the water phase to the interfacial layer, rapidly reducing the IFT. In conclusion, the cationic-anionic Gemini surfactant mixtures exhibit superior interfacial activity, which may promote the application of Gemini surfactant.     

A Star-Shaped Anionic Surfactant: Synthesis,Alkalinity Resistance,Interfacial Tension and Emulsification Properties at the Crude Oil–Water Interface

In this research, a star‐shaped surfactant was synthesized through the chlorination reaction, alkylation reaction and sulfonation reaction of triethanolamine, which is composed of three hydrophobic chains and three sulfonate hydrophilic groups. The critical micelle concentration (CMC) of the surfactant was measured by the surface tension method, and the results showed that it had high surface activity with CMC of 5.53 × 10^?5 mol/L. The surfactant was superior in surface active properties to the reference surfactants SDBS and DADS‐C₁₂. The interfacial tension (IFT) of the studied crude oil–water system (surfactant concentration 0.1 g/L, NaOH concentration 0.5 g/L, and experimental temperature 50 °C) dropped to 1.1 × 10^?4 mN/m, which can fulfil the requirement of surfactants for oil displacement. An aqueous solution of the surfactant and crude oil was emulsified by shaking, which formed a highly stable oil‐in‐water (O/W) emulsion with particle size of 5–20 μm. The oil displacement effect was almost 12%.     

A Chemical equilibrium model for interfacial activity of crude oil in aqueous alkaline solution: The effects of pH,alkali and salt

A chemical equilibrium model is proposed to describe the effects of acid content, pH and sodium ion concentration on the interfacial activity of crude oil in aqueous alkaline solutions. The model is based on an equilibrium among the dissociation of acids in the crude, the dissociation of the sodium salt containing the active species and the dissociation of water. It is shown that once the pH of the interface reaches the pK_a of the acids, the interfacial tension (IFT) drops steeply and that further addition of sodium ions increases the IFT by shifting the equilibrium to form undissociated soap.     

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.     

Thermodynamic Parameters and Interfacial Properties of Poly(ethylene glycol)-octyl Sulfosuccinates

Surface tension of a series of poly(ethylene glycol)-octyl sulfosuccinates at different temperatures was measured, and the interfacial properties were investigated in the absence and presence of inorganic salts. Surface tension results indicate that critical micelle concentration (CMC) values of five surfactants (C8-PEG200, C8-PEG400, C8-PEG600, C8-PEG800, and C8-PEG1000) decrease as the molecular weight of polyethylene glycol (PEG) segments and the experimental temperature increases. The surface activity of the C8-PEG series changes with temperature, and the surface tension at the CMC (γ_CMC) of the C8-PEG series decreases initially and then increases as the PEG molecular weight increases. This behavior may be attributed to the dehydration of the surfactant molecules, resulting in the change of hydrophile–lipophile balance for the different EO numbers in the surfactant molecules, which form a different surface energy film at the air–water interface. Negative ΔG_m indicates that the micellization process of these surfactants is spontaneous and an entropically driven process. For the water/alkane interface, these surfactants have low interfacial activity. The interfacial tension (IFT) between these surfactants and alkanes increases first and then decreases with the increase in the molecular weight of PEG segments. After the addition of salt, the interfacial activity of the investigated surfactants increases significantly. The IFT between C8-PEG800 and 10–12 alkanes and between C8-PEG1000 and 12–16 alkanes reaches a low IFT magnitude of 10⁻² mN m⁻¹ in the presence of 0.5% CaCl₂ or the mixed inorganic salts 0.5% NaCl+0.5% CaCl₂.     

Investigation of Interfacial Tension Reduction,Wettability Alteration,and Oil Recovery Using a New Non-ionic Oil-Based Surfactant from Gemini Surfactants Family Coupled with Low-Salinity Water: Experimental Study on Oil-Wet Carbonate Rock

Low-salinity surfactant (LSS) flooding is a combined enhanced oil recovery (EOR) technique that increases oil recovery (OR) by altering the rock surface wettability and reducing oil–water interfacial tension (IFT). In this study, optimum concentrations of several types of salt in distilled water were obtained on the basis of IFT experiments for the preparation of low-salinity water (LSW). Then, a new oil-based natural surfactant (Gemini surfactant, GS) was combined with LSW to investigate their effects on IFT, wettability, and OR. Experimental results showed that LSW is capable of reducing IFT and contact angle, but the synergy of GS and the active ions Mg²⁺, Ca²⁺, and SO₄²⁻ in LSW was more effective on IFT reduction and wettability alteration. The combination of 1000 ppm MgSO₄ and 3000 ppm GS led to a decrease in contact angle from 134.82° to 36.98° (oil-wet to water-wet). Based on core flooding tests, LSW injection can increase OR up to 71.46% (for LSW with 1000 ppm MgSO₄), while the combination of GS and LSW, as LSS flooding, can improve OR up to 84.23% (for LSS with 1000 ppm MgSO₄ and 3000 ppm GS). Therefore GS has great potential to be used as a surfactant for EOR.     

Effects of Divalent Salts on the Interfacial Activity of the Mixed Surfactants at the Water/Model Oil Interface

In our previous report, the mixed cationic/anionic surfactant system consisting of N-dodecyl-N-methylpyrrolidinium bromide (L12) and sodium dodecyl sulfate (SDS) showed good interfacial tension (IFT) reduction of water/model oil (V_toluene:V _n-decane = 1:1). In the present study, the effects of divalent salts (MgCl₂ or CaCl₂) on the interfacial activity were systematically evaluated. The additional Mg²⁺ ions greatly reduced the IFT to an ultralow value, whereas Ca²⁺ ions caused the generation of the precipitates and resulted in increased IFT values. The precipitates disappeared in binary divalent salt solutions, and the IFT values remained at a low level. Based on the valence, polarizability, and hydrated radius of the ions, we proposed a model to explain the abnormal changes. The effects of NaCl and temperature were investigated to further verify our proposed mechanism. Moreover, the additional divalent salts obviously enhanced the stability of L12/SDS stabilized emulsions.     

Novel Alkyl Ether Sulfonates for High Salinity Reservoir: Effect of Concentration on Transient Ultralow Interfacial Tension at the Oil–Water Interface

The effect of surfactant concentration on the occurrence and detection of transient ultralow interfacial tension (IFT) between crude oil and formation water at 75 °C has been investigated using a series of novel sodium alkyl ether sulfonates having various increasing molecular weights and degrees of ethoxylation. All surfactant systems displayed dynamic interfacial tension (DIT). Transient ultralow DIT (DIT_min) were detected only within an intermediate surfactant concentration. This behavior was attributed to an implicit concentration-related length scale required for the added surfactant to diffuse from the bulk phase to the freshly prepared oil–water interface. In the high surfactant concentration range, this length scale is relatively short and results in an instantaneous (and undetectable) occurrence of DIT_mim in a relatively very short time scale, well beyond the detection limit of the spinning drop tensiometer (~2–3 min). Interestingly, DIT_min were detected only in systems above the surfactant’s critical micelle concentration, suggesting that DIT_min occurs as a result of the diffusion (subsequent to the adsorption) of the oil acidic species from the interface to the bulk phase to form mixed micelles with the added surfactant. Measurements of DITs in the presence of decane showed no evidence for DIT_min, confirming the general belief that DIT_min is indeed due to the interaction of the added surfactant with the oil acidic components. Finally, the effect of surfactant concentration on the equilibrium IFT (γ_eq) showed evidence for relatively low values (~10⁻² mNm⁻¹) for some surfactant systems.     

Effect of salts and their interaction with ingenious surfactants on the interfacial tension of crude oil/ionic solution

Understanding the roles of asphaltene and resin as natural surfactants existed in crude oil can enlighten contradicting reported results regarding interfacial tension(IFT) of crude oil/aqueous solution as a function of salinity and ion type. In this way, this study is aimed to investigate the effect of these natural surface active agents on IFT of with special focus on SO_4~(2-)anion and Mg~(2+)cation. Two different synthetic oil solutions of 8 wt% of the extracted asphaltene and resin dissolved in toluene are prepared, and then IFT values are measured. After that,the obtained results are compared with the IFT of intact crude oil in contact with the same saline solutions examined in the previous stage. The obtained results showed a synergistic effect of Na_2SO_4+ MgCl_2 solution unlike the MgSO_4+ MgCl_2 and CaSO_4+ MgCl_2 solutions on IFT reduction of resin at MgCl_2 concentration of 15000 mg·kg~(-1). In summary, it is found that the affinity of asphaltene molecules towards the interface of oleic phase/ionic solution leads to higher IFT variation.     

双-十二醇聚氧乙烯醚甲基羧基甜菜碱的合成及性能

双十二烷基甲基甜菜碱(diC₁₂B)是一种优良的无碱驱油用表面活性剂,但由于亲油性太强,在水中的溶解性较差,并且在油砂表面具有较大的吸附量。本文试图在diC₁₂B分子中引入EO基团,以改善其性能。为此以溴代十二烷和三缩四乙二醇为原料合成了单分布的十二醇聚氧乙烯(4)醚,再经氯代并与一甲胺和氯乙酸锂反应,最终合成了双十二醇聚氧乙烯(4)醚甲基羧基甜菜碱(diC₁₂EO₄B)。产物经核磁和质谱表征,证明与目标产物的分子结构相符。与diC₁₂B相比,diC₁₂EO₄B在水中的溶解度显著增加,25℃时达到1.5×10^-4mol/L,是diC₁₂B 的3倍左右,45℃下在石英砂/水界面的饱和吸附量是diC₁₂B的70%左右。diC₁₂EO₄B保留了diC₁₂B的高表面活性,如较低的临界胶束浓度,1.6×10^-5mol/L;较高的降低表面张力的效能,g_cmc=29.3mN/m;在空气/水界面具有较大的饱和吸附量,6.5×10^-10mol/cm²;和较小的分子截面积,0.26nm²。diC₁₂EO₄B具有优良的降低油/水界面张力的能力,45℃下单独能将大庆地层水/C₇~C₉正构烷烃界面张力降至10^-3mN/m数量级,将大庆原油/地层水的界面张力降至10^-2mN/m数量级。通过与亲油性表面活性剂diC₁₂B以及C₁₆B复配,能在0.0625~5mmol/L总浓度范围内将大庆原油/地层水的界面张力降至10^-3mN/m数量级,无需加入任何碱或电解质。     

Novel Star Polymeric Nonionic Surfactants as Crude Oil Emulsion Breakers

The principle focus of this work is to address the issues associated with the existence of water in crude oil, especially corrosion, scaling, viscosity, and catalyst suppression problems. This work aims to prepare star polymer nonionic surfactants based on (2Z,2′Z,2″Z)-4,4′,4″-((nitrilotris(ethane-2,1-diyl))tris(oxy))tris(4-oxobut-2-enoic acid) to be used as demulsifiers. To achieve this aim, maleic anhydride was reacted with triethanolamine followed by esterification with the polyethylene oxide polypropylene oxide copolymer (PPO-PEO 5000) and silicone polyether (ABIL B 8843). The chemical structure of the prepared compounds was assessed using gel permeation chromatography (GPC), Fourier transform infrared (FT-IR), and ¹H NMR. Demulsifier performance was determined by quantifying surface tension (ST), dynamic interfacial tension and interfacial rheology, partition coefficient (PC), and relative solubility number (RSN). The efficacy of the prepared emulsion breakers on asphaltenic crude oil emulsion was examined using the bottle test. The research results demonstrated that the prepared breaker based on the silicone polymer was more efficient in breaking the asphaltenic crude oil emulsion than a block copolymer and EO/PO-based copolymers at 1500 ppm and after 120 min.     

Synthesis,Surface Activity,and Biological Activities of Phosphonium and Metronidazole Salts

A series of phosphonium amphiphilic compounds was synthesized. Cationic parts of molecules contain triphenylphosphonium moieties. Lipophilic parts of compounds are represented by straight alkyl chain or the alkyl chains which are ornamented by benzyl or metronidazole. The physicochemical properties of phosphonium amphiphilic compounds were investigated by the measurements of surface tension and conductivity. The critical micelle concentration (cmc), the surface tension value at the cmc (γ_cmc), the surface area at the surface saturation per head group (A_cmc) were determined. The lowest cmc value was determined for phosphonium salts with straight dodecyl alkyl chain. Its value was 1.5 × 10⁻³ mol dm⁻³. Surface tension at the cmc decreases with the addition of bulky moieties (benzyl, radical from metronidazol) at the end of alkyl chains. Biological activities of compounds were studied on human erythrocytes and strains of Acanthamoeba lugdunensis and Acanthamoeba quina. Dodecyltriphenylphosphonium bromide showed the highest activity against Acanthamoeba. To the best of our knowledge, it is the first compound of the group of phosphonium amphiphiles, which exhibited high activity against Acanthamoeba. The determined structure–activity relationship indicated nonspecific trophocidal and hemolytic activity that depends on physicochemical properties of the studied compounds.