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The sketches of stabilization mechanism of emulsion stabilized by a HMPAM and b HMPAM with salts (the HMPAM concentration is above CAC)
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The emulsification of amphiphilic polymer is inevitably affected by the salinity environment in the preparation and flooding process. The variation of emulsions in stability and rheology has a significant influence on the efficiency of polymer flooding. Thus, the effect of NaCl and CaCl2 on the emulsification behavior of hydrophobically modified po...
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... It could be obviously found that the viscosity of ISEPAM first slightly increased within a concentration range not exceeding 750 mg/L and then exhibited an increase with continuously increasing concentration, which generally indicates the existence of critical associating concentration (CAC). Moreover, the viscosifying property increases when the content of divalent ions increases to a certain degree [28]. When the polymer solution's electrolyte content increases (salinity increased from 2410 mg/L to 4456 mg/L), the polymer solution's polarity increases so that the hydrophobic association is enhanced, and the viscosity of the solution increases. ...
The development of oil and gas resources in low-permeability reservoirs is being paid more and more attention. Moreover, oil and gas resources in low-permeability reservoirs are affluent, and the water cut of the medium permeability layer is so high that the injection capacity has decreased significantly. Therefore, it is of great importance to address the issues of injectability and enhance oil recovery in low-permeability reservoirs. Given the existing conditions of low permeability and high water cut in Daqing Oilfield, the synthesis of an in situ emulsified associative polymer (ISEPAM) is the focus of the research. The polymer was prepared by micellar polymerization, ensuring a molecular weight of 5 × 10⁶ Dalton. A series of experiments were conducted to investigate its dissolution filtration property, viscosifying, emulsification, anti-adsorption, conductivity, and oil displacement capacity. The experimental results show that ISEPAM has more significant properties than the polymeric surfactant (HB) used in Daqing Oilfield. The ISEPAM solution has significant filterability (filter factor is 1.1), viscosifying (38.66 mPa·s), emulsification (the water evolution rate of ISEPAM was only 4.4% for 60 min at 90% water cut), and good anti-adsorption property (after five adsorptions, still has a viscosity retention rate of 65%) in a specific concentration (1000 mg/L) and the field water in Daqing Oilfield (salinity is 4996.3 mg/L). The reason for this is due to the presence of dynamic reversible networks in the ISEPAM solution, and there are no cationic functional groups on the polymer chain. The conductivity of ISEPAM was tested using a homogeneous square core with 48.1 mD permeability, and the results show that the viscosity retention rate of the effluent can reach 90% and excellent injection property can be achieved. In the oil displacement test, ISEPAM presents excellent sweep efficiency and enhanced oil recovery by about 25% under 50 mD permeability. Under low permeability conditions, the ISEPAM exhibits better injectability and excellent oil displacement capacity. The related findings can provide an important idea and reference for the design and development of EOR polymers in the reservoirs with low permeability or high water cut.
... The implementation of polymer flooding has substantially improved the stability of oil-water emulsions, posing challenges for demulsification and dehydration [19][20][21][22][23][24]. Polymers can increase the viscosity and elastic modulus of the oil-water interface, resulting in a more rigid interface film and prolonging the coalescence time between droplets [25]. ...
... These methods were inefficient in breaking the emulsion of oily sludge, thus causing inadequate dewatering performances. Moreover, the microwave and ultrasound treatment might generate secondary fine water droplets and solid particles, which were more easily to be adsorbed on the water/oil interface to increase the stability of emulsion (Frelichowska et al. 2010;Katepalli et al. 2017;Lu et al. 2018). In contrast, chemical methods were efficient for breaking the emulsion by destroying the high-viscosity substances on the water/oil interface, hence compelling the emulsions transform to an unstable state (He et al. 2019;Pensini et al. 2014). ...
Highly efficient dewatering is essential to the reduction and reclamation disposal of oily sludge, which is a waste from the extraction, transportation, and refining of crude oil. How to effectively break the water/oil emulsion is a paramount challenge for dewatering of oily sludge. In this work, a Fenton oxidation approach was adopted for the dewatering of oily sludge. The results show that the oxidizing free radicals originated from Fenton agent effectively tailored the native petroleum hydrocarbon compounds into smaller organic molecules, hence destructing the colloidal structure of oily sludge and decreasing the viscosity as well. Meanwhile, the zeta potential of oily sludge was increased, implying the decrease of repulsive electrostatic force to realize easy coalescence of water droplets. Thus, the steric and electrostatic barriers which restrained the coalescence of dispersed water droplets in water/oil emulsion were removed. With these advantages, the Fenton oxidation approach derived the significant decrease of water content, in which 0.294 kg water was removed from per kilogram oily sludge under the optimal operation condition (i.e., pH value of 3, solid–liquid ratio of 1:10, Fe²⁺ concentration of 0.4 g/L and H2O2/Fe²⁺ ratio of 10:1, and reaction temperature of 50 °C). In addition, the quality of oil phase was upgraded after Fenton oxidation treatment accompanying with the degradation of native organic substances in oily sludge, and the heating value of oily sludge was increased from 8680 to 9260 kJ·kg⁻¹, which would facilitate to the subsequent thermal conversion like pyrolysis or incineration. Such results demonstrate that the Fenton oxidation approach is efficient for the dewatering as well as the upgrading of oily sludge.
... This is because, under the condition of high mass fraction, more DA (EO) 5 GE-g-HEC particles are adsorbed on the oil-water interface, forming a higher interfacial film area, thus reducing the particle size of the emulsion and making the emulsion more stable [44,45]. The relationship between emulsion stabilization mechanism and rheology is complex and intimate [46]. The rheological properties of emulsions stabilized by DA(EO) 5 GE-g-HEC with different mass fraction (0.05%, 0.1%, 0.2%, 0.4%) were analyzed and discussed. ...
... 22 Generally, these experimental attempts were performed in sandstone reservoirs under low brine concentration and regular temperature below 100 C. Several investigations were developed by different authors and reported the impact of the polymer architecture, molar composition, salt concentration, and temperature on the ability of these prepared materials to be used as rheological modifiers in the EOR process. [23][24][25][26][27][28][29][30][31][32][33][34][35][36][37][38][39][40][41] In this work, an associative water-soluble terpolymer was synthesized, characterized, and evaluated at laboratory level in order to determine its performance to act as a thickening agent, that is, a potential candidate to improve the oil recovery process. Experiments were performed in the presence of heavy crude oil sample from a carbonated reservoir located in southern México. ...
In this work, a thermo‐responsive hydrophobically associative water‐soluble terpolymer was prepared and evaluated as polymer flooding in laboratory tests versus a heavy crude oil from a carbonated reservoir in southern Mexico. Terpolymer of acrylamide, N‐isopropylacrylamide and N,N′‐dihexylacrylamide were synthesized via micellar free radical polymerization. Reaction was carried out at 50°C using sodium dodecyl sulfonate as surfactant and 4‐(4′‐azobis)cyanovaleric acid as initiator. The terpolymer was characterized by nuclear magnetic resonance. Steady shear viscosity of polymer solutions at different concentrations was determined in the presence of NaCl (from 1 to 5 wt%) at different temperatures (from 25 to 120°C). Heavy crude oil sample was characterized and revealed a viscosity of 2. 26 Pa s, 10.21° API with a content of Saturates, Aromatics, Resins, Asphaltenes of 26.4, 38.5, 22.3, and 12.8, respectively. The crude oil recovery of polymer at 2 and 3 wt% revealed a surface tensions of 49.6 and 48.2 mN × m and adsorption capacities of 1.33 and 1.77 wt%. Finally, polymer solutions at 2 and 3 wt% showed a contact angle between 29.6 and 26.5° and a crude oil recovery of 68.3 and 75.3%, respectively.
... In order to improve the EOR technology, polymeric surfactants, which are surfactants with high molecular weight and simultaneously contain a hydrophilic group and a hydrophobic group in their molecular chain, have been developed rapidly [7][8][9][10]. Polymeric surfactants generally have an good thickening ability and properties such as strong shear resistance, salt resistance, and temperature resistance [11,12]. Moreover, the presence of hydrophobic groups contributes to the interfacial tension reduction and good emulsification effect for crude oil [13][14][15][16][17][18]. ...
Polymeric surfactant flooding is an effective method to improve oil recovery, and the stability of the emulsion is closely related to the effect of surfactant flooding. The preparation method for a surfactant-stabilized emulsion is relatively simple, and the emulsion produced by the existing device cannot simulate the real formation conditions. To better simulate the emulsification of polymeric surfactant during formation and to study the influencing factors of emulsion stability, a new sieve plate rotary emulsification device was used to prepare emulsions instead of the traditional high-speed shear emulsifier, and the stability of emulsions prepared by different methods was compared. The parameters of the device were optimized by determining the water content, particle size, and Turbiscan Stability Index TSI (stability parameter) of the emulsion. The factors affecting the stability of the emulsion were studied by using the optimized experimental device. The results showed that the optimized parameters of the sieve plate rotary emulsification device were 5 sieve plates, diameter of 1 mm, and emulsification time of 60 min. The stability of the emulsion prepared by the new device was better than that of the emulsion prepared by the traditional high-speed stirrer, which can be attributed to the more abundant contact and mix of oil and surfactant solution. Meanwhile, as the polymeric surfactant concentration, salinity, and water–oil ratio increased, the stability of the polymeric surfactant emulsion increased. The results of this study provide a theoretical basis and guidance for better simulation of polymeric surfactant migration and emulsification during formation.
... The analyzer is equipped with a pulsed near-infrared light source (λ = 880 nm) and synchronous optical detectors, which determine the intensity of backscattering (BS) light. 39 of the sample reflect the microscopic characteristic of growth or migration of oil droplets at a given time. ...
... Multiple-light scattering is a common method to investigate the stability of emulsions. Its specific research method and mechanism can be referred from the published work of Lu et al. 39 Figure 8 shows the results of an oil/TPVR7-0.5% emulsion and an oil/TPVR7-0.5% + DSS-0.5% emulsion, respectively, where the x axis represents the height of the emulsion, the y axis represents the variation percent of the backscattering light intensity relative to the initial state, and the colors of the spectra represent the various testing times. ...
In-situ emulsion formation is an effective non-thermal method to improve conventional heavy oil recovery. In this paper, a newly designed viscosity reducer (TPVR7) and a high performance surfactant (DSS) for enhanced conventional heavy oil recovery have been introduced and evaluated. Dewatering rate test, emulsion droplet size measurement, multiple-light scattering and interfacial tension are carried out to evaluate the synergistic effect of viscosity reducer and surfactant on emulsion stability and efficiency in enhancing heavy oil recovery. The results show that adding surfactant can significantly increase the emulsion stability by decreasing the size of the emulsion droplet and forming a tighter interfacial film. The optimum viscosity reducer-surfactant system is formulated as TPVR7-0.5%+DSS-0.5%. With the optimum system, the viscosity of heavy oil decreased from 350mPa•s to 9mPa•s. And the equilibrium interfacial tension of oil/TPVR7-0.5%+DSS-0.5% solution is ~0.092mN/m, much lower than that of oil/TPVR7 solution. The mechanisms of synergistic collaboration between viscosity reducer and surfactant includes enhancing emulsion stability, viscosity reduction, and interfacial tension reduction. The sand-pack flooding experiments show that viscosity reducer and surfactant could improve heavy oil recovery by 21.89% after water flooding at the optimum concentration, which indicates that viscosity reducer and surfactant flooding has great potential to enhance heavy oil recovery.
... Different hydrophobic monomers were reported, such as di-alkyl substituted acrylamides di-n-propylacrylamide, di-n-octylacrylamide [1], N,N-dihexylacrylamide or N,N-diphenylacrylamide [2], N-octadecylacrylamide [3], sodium 2-acrylamido-tetradecane sulfonate [4], 3-acrylamido-2-hydroxypropyl triakylam monium chloride [5], poly(propylene glycol) monomethacrylate [6], isomeric 11-acrylamidoundecanoic acid [7], stearyl methylacrylate [8], sodium 9-(and 10)-acrylamidostearate [9], etc. Due to the intramolecular and intermolecular interaction between the hydrophobic groups, the enlargement of hydrodynamic volume of polymers increases the viscosity of hydrophobically modified polyacrylamide aqueous solutions, and intermolecular association may further enhance the viscosity [10]. e aqueous solution of these polymers is expected to show special properties, including temperature, salt, and shear resistances [11,12]. e viscosity of hydrophobically modified polyacrylamide solution does not decrease at high salinity when its concentration is larger than the critical aggregation concentration [13]. ...
The adsorption of polymers affects the cost and oil recovery in oil reservoir exploitation and the flocculation effect in the treatment of oil sand tailings. The adhesion and adsorption of a hydrophobically modified polyacrylamide (HMPAM), i.e., P(AM-NaAA-C 16 DMAAC), on silica and asphaltene were investigated using surface force measurements, thermodynamic analysis and quartz crystal microbalance with dissipation (QCM-D) measurement. Our study indicates that HMPAM polymer has strong interaction with both silica and asphaltene. The adhesion force of HMPAM on silica was stronger than that on asphaltene surface. Consistently, the adsorption of HMPAM was also greater on silica surface, with a more rigid layer formed on the surface. For HMPAM/silica system, the attractive interaction and the strong adhesion are mainly driven by the hydrogen bonding and electrostatic interaction. For HMPAM/asphaltene system, it is mainly due to hydrophobic interaction between the long hydrocarbon chains of HMPAM and asphaltene. Furthermore, continuous adsorption of HMPAM was detected and multiple layers formed on both silica and asphaltene surfaces, which can be attributed to the hydrophobic chains of HMPAM polymers. This work has illustrated the interaction mechanism of HMPAM polymer on hydrophilic silica and hydrophobic asphaltene surfaces, which provide insight into the industrial applications of hydrophobically modified polymer.
... 12,13 There is a large amount of metal ions in water, which can hinder the dispersion of polymers in the aqueous solution and decrease the apparent viscosity. [14][15][16] To solve these problems, various functional groups are grafted on the polyacrylamide chain, such as a hydrophobic monomer [17][18][19] or a sulfonate group. 20 A polymer containing a sulfonate group can be tolerant to high salinity and more stable when swelling in water. 1 Many researchers have examined the interaction between the salt ion and polyacrylamide, [21][22][23][24] but there are no clear conclusions to explain the interaction mechanism, particularly through the effect of ions on the morphology of polyacrylamide. ...
Ca²⁺ tolerance of water‐soluble polyacrylamide is a key problem in application fields. It is urgent to make the mechanism of between the polyacrylamide and Ca²⁺ clear. A terpolymer polyacrylamides including the sulfonate group with different monomer concentrations is synthesized. The effect of the CaCl2 concentration on the rheological properties is measured by a rheological rheometer. The zeta potential of the copolymer solution is obtained by a zeta potentiometer to learn about the electrical characteristics of the copolymers in solution. The microcosmic shape of the copolymer aqueous solution is investigated by a laser particle analyzer and an environmental scanning electron microscope. The results show that more sulfonate groups on the molecule can enhance the salt tolerance of the polyacrylamide. Sulfonate groups can weaken the effect of Ca²⁺ on the copolymer through the formation of complexes, whereas the self‐aggregation process of the copolymer cannot be stopped at high Ca²⁺ concentrations. This study provides theoretical guidance to elucidate the influencing rules and mechanism of calcium salt on the polyacrylamide containing a sulfonate group, which can be helpful for polyacrylamide modification and can improve the application of polyacrylamide under the condition of higher salt concentration. © 2019 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2019, 136, 47539.
