Novel fluorinated surfactants for enhanced oil recovery in carbonate reservoirs

Novel surfactant‐polymer (SP) formulations containing fluorinated amphoteric surfactant (surfactant‐A) and fluorinated anionic surfactant (surfactant‐B) with partially hydrolyzed polyacrylamide (HPAM) were evaluated for enhanced oil recovery applications in carbonate reservoirs. Thermal stability, rheological properties, interfacial tension, and adsorption on the mineral surface were measured. The effects of the surfactant type, surfactant concentration, temperature, and salinity on the rheological properties of the SP systems were examined. Both surfactants were found to be thermally stable at a high temperature (90 °C). Surfactant‐B decreased the viscosity and the storage modulus of the HPAM. Surfactant‐A had no influence on the rheological properties of the HPAM. Surfactant‐A showed complete solubility and thermal stability in seawater at 90 °C. Only surfactant‐A was used in adsorption, interfacial tension, and core flooding experiments, since surfactant‐B was not completely soluble in seawater and therefore was limited to deionized water. A decrease in oil/water interfacial tension (IFT) of almost one order of magnitude was observed when adding surfactant‐A. However, betaine‐based co‐surfactant reduced the IFT to 10^?3 mN/m. An adsorption isotherm showed that the maximum adsorption of surfactant‐A was 1 mg per g of rock. Core flooding experiments showed 42 % additional oil recovery using 2.5 g/L (2500 ppm) HPAM and 0.001 g/g (0.1 mass%) amphoteric surfactant at 90 °C.     

Surface Rheological Properties of Hydrophobically Modified Polyacrylamide and Imidazolium Surfactant Systems

The dilational rheological properties of hydrophobically modified polyacrylamide (HMPAM) or hydrolyzed polyacrylamide (HPAM) solutions without and with imidazolium surfactants ([C₁₄‐4‐C₁₄im]Br₂ and [C₁₄mim]Br) at the air/water surface were investigated using oscillating bubble measurements. The results obtained suggest that imidazolium surfactants interact with the polymer on the surface, enhancing the dilational viscoelasticity of surface film. The dilational modulus value of [C₁₄‐4‐C₁₄im]Br₂/HMPAM is higher than that of the [C₁₄mim]Br/HMPAM system at low polymer concentration, confirming that [C₁₄‐4‐C₁₄im]Br₂ with two head groups and two hydrophobic chains can combine with a polymer to form a strong film on the surface. Moreover, imidazolium surfactants have stronger hydrophobic interaction with HMPAM chains than those of HPAM, thus enhancing the surface film strength for a surfactant/HMPAM system. The surface interaction mechanism between polyacrylamide and imidazolium surfactant is proposed to result from the electrostatic interactions and the hydrophobic effect.     

Effects of Polyether Surfactants on Dynamic Interfacial Tension of Betaine Solutions against Crude Oil

The dynamic interfacial tension (IFT) of betaine and betaine/polyether‐nonionic surfactant‐mixed systems against hydrocarbons, kerosene, and crude oil–water was studied using a spinning‐drop tensiometer. The influence of average molecular weight of polyether‐nonionic surfactants on IFT of mixed solutions was investigated. On the basis of the experimental results, one can find that it is difficult to reach the ultralow IFT value for betaine solution against hydrocarbon and kerosene because of the mismatch between the hydrophobic and hydrophilic groups. After purification, kerosene still contains a small amount of carboxyl groups, which can exert a synergistic effect on surfactants resulting in a lower IFT. The IFT of betaine and mixtures against Daqing crude oil can reach an ultralow value because of the mixed adsorption of surfactant and petroleum soap molecules. For mixed solutions, with the increasing concentration of added polyether, the decrease of petroleum soaps at the oil–water interface results in the destruction of synergistic effects.     

The Effects of Dynamic Noncovalent Interaction between Surfactants and Additional Salt on the pH-Switchable Interfacial Tension Variations

The dynamic noncovalent interaction between the anionic surfactant sodium dodecyl benzene sulfonate (SDBS) and 1,3-diphenylguanidine (DPG) was employed to control the interfacial activity of the surfactant. At high HCl concentration (1000 mg L⁻¹), the SDBS/DPGⁿ⁺ system could reduce the water/oil interfacial tension (IFT) to 10⁻⁴ mN m⁻¹ order of magnitude, which was much lower than the IFT values in the SDBS/DPG⁺ system with a low HCl concentration (100 mg L⁻¹) and the individual SDBS system by three and four orders of magnitude, respectively. The pH-switchable protonation of amido groups in DPG molecules determines the SDBS/DPG molecular interaction and the amplitude of IFT reduction, which was confirmed by control experiments using two other surfactants (sodium dodecyl sulfate [SDS] and dodecyl trimethylammonium bromide [DTAB]). Moreover, the investigation of the NaCl and temperature effects on the IFT indicated the intensity of mixed SDBS/DPGⁿ⁺ adsorption layers at the water/oil interface.     

Properties of hydrophobically modified polyacrylamide with low molecular weight and interaction with surfactant in aqueous solution

Hydrophobically modified polyacrylamide (HMPAM), with a molecular weight of 10⁴ g/mol, was studied using a range of rheological methods and dynamic light scattering (DLS). DLS measurements indicate that the association of the modified polymer begins at low concentration. The modified polymer with high substitution forms transient networks below the critical concentration, but the networks are disrupted by the micelles formed by the polymer itself, and the networks do not contribute to viscosity enhancement. The modified polymers exhibited surface activity, and so they may be regarded as nonionic polymeric surfactants rather than thickeners. On the other hand, HMPAM is shown to interact with the surfactant SDS while PAM is inert to SDS. In the hydrophobic domains, it undergoes a surfactant‐induced association process; in the hydrophobe‐surfactant transition regions, the surfactant binds to the polymer in a noncooperative way and forms a polymer–surfactant complex. Contracted polymer chains begin to extend because of electrostatic repulsion, which can overcome the association at surfactant domains. The conformation of HMPAM polymer chains could be controlled by adding a specific amount of surfactant. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 100: 4348–4360, 2006     

Viscoelastic Surfactants with High Salt Tolerance,Fast‐Dissolving Property,and Ultralow Interfacial Tension for Chemical Flooding in Offshore Oilfields

Injected chemical flooding systems with high salinity tolerance and fast‐dissolving performance are specially required for enhancing oil recovery in offshore oilfields. In this work, a new type of viscoelastic‐surfactant (VES) solution, which meets these criteria, was prepared by simply mixing the zwitterionic surfactant N‐hexadecyl‐N,N‐dimethyl‐3‐ammonio‐1‐propane sulfonate (HDPS) or N‐octyldecyl‐N,N‐dimethyl‐3‐ammonio‐1‐propane sulfonate (ODPS) with anionic surfactants such as sodium dodecyl sulfate (SDS). Various properties of the surfactant system, including viscoelasticity, dissolution properties, reduction of oil/water interfacial tension (IFT), and oil‐displacement efficiency of the mixed surfactant system, have been studied systematically. A rheology study proves that at high salinity, 0.73 wt.% HDPS/SDS‐ and 0.39 wt.% ODPS/SDS‐mixed surfactant systems formed worm‐like micelles with viscosity reaching 42.3 and 23.8 mPa s at a shear rate of 6 s^?1, respectively. Additionally, the HDPS/SDS and ODPS/SDS surfactant mixtures also exhibit a fast‐dissolving property (dissolution time <25 min) in brine. More importantly, those surfactant mixtures can significantly reduce the IFT of oil–water interfaces. As an example, the minimum of dynamic‐IFT (IFT_min) could reach 1.17 × 10^?2 mN m^?1 between the Bohai Oilfield crude oil and 0.39 wt.% ODPS/SDS solution. Another interesting finding is that polyelectrolytes such as sodium of polyepoxysuccinic acid can be used as a regulator for adjusting IFT_min to an ultralow level (<10^?2 mN m^?1). Taking advantage of the mobility control and reducing the oil/water IFT of those surfactant mixtures, the VES flooding demonstrates excellent oil‐displacement efficiency, which is close to that of polymer/surfactant flooding or polymer/surfactant/alkali flooding. Our work provides a new type of VES flooding system with excellent performances for chemical flooding in offshore oilfields.     

Amido-Amine-Based Cationic Gemini Surfactants: Thermal and Interfacial Properties and Interactions with Cationic Polyacrylamide

Experimental studies were conducted to investigate thermal and interfacial properties of two in‐house synthesized amido‐amine‐based cationic gemini surfactants namely: dodecanoic acid [3‐({4‐[(3‐dodecanoylamino‐propyl)‐dimethyl‐amino]‐butyl}‐dimethyl‐amino)‐propyl]‐amide dibromide ( 12‐4‐12 ) and dodecanoic acid [3‐({6‐[(3‐dodecanoylamino‐propyl)‐dimethyl‐amino]‐hexyl}‐dimethyl‐amino)‐propyl]‐amide dibromide ( 12‐6‐12 ). Thermogravimetric analysis showed the excellent thermal stability of surfactants and no structural degradation was observed at temperatures up to 250 °C. The long‐term thermal stability of the surfactants was investigated with the aid of spectroscopic techniques such as nuclear magnetic resonance (NMR (¹H and ¹³C) and Fourier transform infrared (FTIR) spectroscopy. Both surfactants were found to be thermally stable, and no changes in structure were observed after aging for 10 days at 90 °C. The interfacial tension of the surfactants was measured at three different temperatures (30, 60, and 80 °C), and the results showed a decrease in interfacial tension with increasing temperature and increasing spacer length of the surfactants. Rheological measurements were used to assess the interactions between the cationic gemini surfactant and cationic polyacrylamide. The addition of cationic surfactant reduced the viscosity and storage modulus of the polymer at low shear rate and frequency due to surfactant–polymer interactions and charge screening. The investigated surfactant–polymer system has great potential in high‐temperature carbonate reservoirs, where conventional anionic surfactants are not recommended due to high adsorption.     

阴离子表面活性剂对聚乙二醇水溶液粘度的影响

测定了聚乙二醇（PEG）在十二烷基硫酸钠（SDS）和琥珀酸双-2-乙己酯磺酸钠（AOT）水溶液中的粘度,讨论了SDS和AOT在水溶液中聚集形态的差异对PEG与SDS和AOT相互作用的不同影响,结果表明：PEG-SDS与PEG-AOT体系粘度均明显增加,而PEG-SDS与PEG-AOT体系粘度变化机制不同,根本原因是表面活性剂在高分子溶液中聚集行为不同,SDS分子在PEG链上聚集,形成类胶束,使高分子链带电,表现出聚电解质的粘度行为;PEG链吸附于AOT囊泡,不同PEG链对囊泡的吸附可能造成高分子链更加伸展,PEG特性粘数增大,使溶液粘度上升。     

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.     

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.     

油水界面上阴/阳离子型复配表面活性剂体系的分子动力学模拟

采油过程中阴/阳离子型表面活性剂复配使用可显著增强驱油效果,对其微观机理的深入研究有助于驱油用表面活性剂的结构优化设计及使用。采用分子动力学方法研究了不同摩尔比的阴离子表面活性剂聚醚羧酸钠(PECNa)和阳离子表面活性剂十八烷基三甲基氯化铵(OTAC)复配体系在油水界面上的分子行为和物理性质。结果表明,复配体系比单种表面活性剂体系更有利于降低油水界面张力。不同复配比体系中,两种表面活性剂头基相反电荷间的吸引作用使表面活性剂之间对各自反离子的静电吸引作用减弱,且等摩尔比体系尤为明显。阴离子表面活性剂的亲水头基对阳离子表面活性剂亲水头基形成的水化层内水分子的结构取向无显著影响,反之亦然。通过调节两种离子型表面活性剂的复配比例,可调整油水界面吸附层微观结构,有望降低油水界面张力,提高采收率。     

Effect of cationic surfactant addition on the drag reduction behaviour of anionic polymer solutions

Although extensive research work has been carried out on the drag reduction (DR) behaviour of polymers and surfactants alone, little progress has been made on the synergistic effects of combined polymers and surfactants. In this work, the interactions between drag‐reducing anionic polymer (copolymer of acrylamide and sodium acrylate, referred to as PAM) and drag‐reducing cationic surfactant (octadecyltrimethylammonium chloride, OTAC) are studied. Solutions are prepared using both deionised (DI) water and tap water. The measurement of the physical properties such as electrical conductivity and viscosity are used to determine the surfactant–polymer interactions. The addition of surfactant to the polymer solution has a significant effect on the properties of the system. The critical micelle concentration (CMC) of the mixed surfactant–polymer system is found to be different from that of the surfactant alone. With the addition of surfactant to a polymer solution, a substantial decrease in the viscosity occurs. The observed changes in the viscosity of mixed polymer–surfactant system are explained in terms of the changes in the extension of polymeric chains, resulting from polymer–surfactant interactions. The anionic PAM chains tend to collapse upon the addition of cationic OTAC. The pipeline flow behaviour of PAM/OTAC mixtures is found to be consistent with the bench scale results. The DR ability of PAM is reduced upon the addition of OTAC. At low concentrations of PAM, the effect of OTAC on the DR behaviour is more pronounced. The DR behaviour of polymer solutions is strongly influenced by the nature of water (DI or tap). © 2011 Canadian Society for Chemical Engineering     

复合碱、盐多元驱各组分对油水界面张力和稠油黏度的影响

无机盐,混合碱NaOH、Na2CO3,阴离子表面活性剂十二烷基苯磺酸钠(LAS)、脂肪醇聚氧乙烯醚硫酸钠(AES),聚合物聚丙烯酰胺(PAM),经过混合组成多元驱。通过实验探讨了该多元驱中各个组分的用量对油水界面张力和稠油黏度的影响,优化了该多元驱中各个组分的含量。实验得出,无机盐的加入可以显著地降低界面张力和稠油黏度。当多元驱中无机盐、混合碱和表面活性剂的质量分数分别为51.87%,40.17%,6.99%,聚合物质量浓度为800 mg/L,配成质量分数为1%的水溶液,加热到50℃,油水质量比7∶3混合后,可使新疆克拉玛依地区红浅稠油黏度从23690 mPa.s降到84.83 mPa.s,降黏率达到99.64%,体系界面张力达到0.07499mN/m。室内评价表明,该多元驱可使新疆克拉玛依地区9#红浅稠油降黏率达到92%。多元驱中无机盐的质量分数超过50%,大大降低了成本。     

Laboratory study of an anti‐temperature and salt‐resistance surfactant‐polymer binary combinational flooding as EOR chemical

Experimental studies were conducted to enhance the oil recovery by a surfactant‐polymer binary combinational flooding system. The surfactant‐polymer binary combinational flooding was obtained by mixing the surfactants with the poly(AM‐NVP‐AS)‐1 which was an anti‐temperature and salt‐resistance tercopolymer and successfully synthesized via free radical polymerization using acrylamide (AM), N‐vinyl pyrrolidone (NVP), allyl sulfonate (AS) as raw materials. The initiator was redox system including water‐soluble azo compound (AIBA·2HCl) and sodium bisulfite (NaHSO₃). Petroleum carboxylate dodecyl dibasic carbonylic acid sodium (C12DAS) and carboxyl betaine dodecyl dimethyl betaine (C12DB) were selected in this article. Compared with the surfactant‐HPAM, the surfactant‐poly(AM‐NVP‐AS)‐1 binary combinational system showed higher apparent viscosity and lower interfacial tension at high temperature and salinity conditions as the result of a better capacity of anti‐temperature, salt‐resistance, and swept volume. The recovery could enhance over 17% based on the core flooding test under the mineralization of 10,000 mg/L at 65°C. © 2013 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2014 , 131, 39984.     

Mixing of Surfactin,an Anionic Biosurfactant,with Alkylbenzene Sulfonate,a Chemically Synthesized Anionic Surfactant,at the n-Decane/Water Interface

Biosurfactants show synergic effects with synthesized surfactant in reducing hydrophobic/hydrophilic interfacial tension, while the understanding of the synergistic mechanism is limited. In the present work, mixed monolayers of surfactin and branched alkylbenzene sulfonate at the n-decane/water interface were studied using atomistic molecular dynamics simulations, and the presence of surfactin affecting the microstructure and dynamic properties of the mixed monolayer was evaluated at molecular level. The density distributions of the surfactants along the direction normal to the interface, radial distribution functions of the surfactant head groups, hydrophobic contacts between surfactants, translational activities of both surfactants and counterions, and the dynamics of the hydrogen bonds formed between surfactant and water were calculated. The results suggested that the structure of the mixed monolayers was more compact than that of the individual system of alkylbenzene sulfonate and the interfacial tension was more efficiently reduced, and the translational activities of both surfactants within the mixed monolayers were much lower. The results implied that biosurfactant surfactin and alkylbenzene sulfonate mixed well at the n-decane/water interface, though they were both anionic surfactants.     

A New Series of Double-Chain Single-Head Sulfobetaine Surfactants Derived from 1,3-Dialkyl Glyceryl Ether for Reducing Crude Oil/Water Interfacial Tension

A new series of sulfobetaine surfactants with double-chain single-head structure were derived from 1,3-dialkyl glyceryl ethers and their performances in reducing Daqing crude oil/connate water interfacial tension (IFT) in the absence of alkali were studied. With a large hydrophilic head group and double hydrophobic chains, these surfactants are efficient at reducing crude oil/connate water IFT. Those with didecyl and dioctyl are good hydrophobic surfactants that can reduce Daqing crude oil/connate water to ultra-low IFT by mixing with a small molar fraction of various conventional single-chain hydrophilic surfactants, such as α-olefin sulfonates, dodecyl polyoxyethylene (10) ether, and cetyl dimethyl hydroxypropyl sulfobetaine. The asymmetric double-chain sulfobetaine derived from 1-decyl-3-hexyl glyceryl ether can reduce Daqing crude oil/connate water IFT to ultra-low solely over a wide concentration range (0.03–10 mM or 0.0017–0.58 wt.%), which allows for use of an individual surfactant instead of mixed surfactants to avoid chromatographic separation in the reservoir. In addition, formulations rich in sulfobetaine surfactants show low adsorption on sandstone, keeping the negatively charged solid surface water-wet, and forming crude oil-in-water emulsions. These new sulfobetaine surfactants are, therefore, good candidates for surfactant-polymer flooding free of alkali.     

Effect of microscopic aggregation behavior on polymer shear resistance

The study of polymer aggregation behavior effect on shear resistance shed light on the synthesis of antishear polymer for oil displacement and enhances the application effect of polymer flooding. The effects of mechanical degradation on the properties of polymer solutions were studied by using partially hydrolyzed polyacrylamide (HPAM), hydrophobically modified HPAM (HMPAM), and dendritic hydrophobic associative polymers (DHAP), which are characterized by “granular,” “chain,” and “cluster” aggregation behavior, respectively. The results show that mechanical shearing can dramatically reduce the performance of polymer solution. The shearing resistance can be effectively enhanced by improving the polymer aggregation behavior. After being strongly sheared, hydrophobically associating polymers can still partially restore its network through hydrophobic association, therefore rebuild the solution viscosity. For DHAP, the broken molecular chains distribute more evenly in solution after shearing. In addition, the strength of reconstructed network structure of DHAP is better than that of HMAPM, which implies a better shear resistance. Furthermore, the hydrophobic association of linear polymers will increase their static adsorption on quartz sand. Meanwhile, DHAP with stronger spatial structure has less static adsorption, which is beneficial to maintain a higher polymer concentration in solution. © 2019 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2019 , 137, 48670.     

Intrinsic viscosity,rheological property,and oil displacement of hydrophobically associating fluorinated polyacrylamide

The surface‐active polymer (FPAM) was synthesized by free‐radical polymerization of acrylamide (AM), 2‐acrylamido‐2‐methyl‐1‐propane sulfonic acid (AMPS) and N ‐dodecyl‐N ‐perfluoro octane sulfonyl acrylamide (AMPD), which was prior prepared by reacting dodecylamine, perfluoro‐1‐octanesulfonyl fluoride, and acryloyl chloride. Parameters affecting the intrinsic viscosity ([η]) and apparent viscosity (η) of FPAM, such as reaction temperature, AMPD concentration, AMPS concentration, monomer concentration, initiator concentration, and pH were examined. Apparent viscosity and interfacial tension (IFT) of FPAM solution were evaluated. Subsequently, temperature tolerance and shear tolerance were investigated by comparing with hydrolyzed polyacrylamide (HPAM), and results indicated that the FPAM displayed better performances than HPAM. FPAM can reduce the IFT between crude oil/water, and the IFT values are around at 2.91 and 3.9 mN m^?1 corresponding to FPAM and HPAM/FC‐118. The sandpack model oil displacement experiment showed that water flooding can further increase the oil recovery to 15.01% (FPAM), compared with 9.26% oil recovery for HPAM, and 10.99% oil recovery for HPAM/FC‐118. The glass micromodel techniques for studying enhanced oil recovery get a good result and provide a useful reference for understanding the displacement behaviors in polymer flood process. It could be concluded that the introduction of fluorinated groups in the polymer chain was helpful in enhancing the oil displacement efficiency. © 2016 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2017 , 134 , 44672.     

Surface and interfacial FTIR spectroscopic studies of latexes. II. Surfactant–copolymer compatibility and mobility of surfactants

Whereas molecular level interactions between sulfonate groups of SDOSS surfactant and COOH groups of EA/MMA copolymer have been discussed in part I of this series, the major focus of this work is to establish the effect of compatibility on the distribution of surfactants at the film–air and the film–substrate interfaces. It is found that the exudation of anionic surfactants is inhibited in neutralized ethyl acrylate/methacrylic acid latex films. On the other hand, nonionic surfactants do not exhibit enrichment at the film interfaces. The inhibited exudation of anionic surfactants is attributed to the increased compatibility resulting from surfactant penetration into the swollen latex particles. This is followed by the formation of solubilized polymer–surfactant complexes through the adsorption of surfactant onto the hydrophobic polymer segments. The effect of neutralization of the carboxylic acid groups on the exudation of anionic surfactants suggests the formation of hydrophobic interactions that overwhelm surface tension effects and prevent surfactant enrichment at either interface.     

Adaptability of a hydrophobically associating polyacrylamide/mixed‐surfactant combination flooding system to the Shengli Chengdao oilfield

We investigated the performance of a combination flooding system composed of hydrophobically associating polyacrylamide (HAPAM) and a mixed surfactant [fatty acid disulfonate anionic gemini surfactant (DMES) plus the nonionic surfactant Triton X‐100 (TX‐100)] under the reservoir conditions of the Shengli Chengdao oilfield. With 1800 mg/L HAPAM and 300–3000 mg/L mixed surfactant, the surfactant–polymer (SP) flooding system reached an ultralow oil–water interfacial tension, and the viscosity of the system was greater than 40 mPa s. After the solution was aged for 120 days, its viscosity was still more than 40 mPa s; this indicated a good aging stability. The core flooding experiments with different porous media permeabilities showed that the SP flooding system created a higher resistance factor and residual resistance factor. In addition, the indoor flooding experiments indicated that the SP combination flooding system increased the enhanced oil recovery by more than 30% over that of the original oil in place compared with the water flooding system. Therefore, it was feasible to use an SP flooding system in the Chengdao oilfield. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2014 , 131, 40390.