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.     

β-Cyclodextrin-functionalized copolymers based on multiple intermolecular forces for enhanced oil recovery

As one of mature enhanced oil recovery (EOR) technologies, polymer flooding has been extensively applied in oilfield. In this study, new hydrophobically associative copolymers were synthesized by free-radical polymerization of acrylamide (AM), acrylic acid (AA), vinyl-modified β-cyclodextrins, and a water-soluble hydrophobic macromonomer (AA-APE-20). Fourier transform infrared, proton-nuclear magnetic resonance, and scanning electron microscopy verified the structure of hydrophobically associative polymers (HDAPAMs). Compared with partially hydrolyzed polyacrylamide (HPAM), multiple intermolecular forces including chelation between ethoxyl (EO) group and Ca²⁺/Mg²⁺, electrostatic bridges between EO groups and carboxyl groups ( COO⁻), hydrogen bonding between EO groups and AM groups ( CONH₂), hydrophobic association among nonyl phenol groups, and host-guest inclusion interaction endowed HDAPAMs favorable temperature-resistance, salt-resistance, and displacement efficiency. It was found that HDAPAMs showed evident temperature-response, salt thickening effect, favorable thixotropy, and viscoelasticity. Compared with HPAM, the core flooding experiments demonstrated that HDAPAMs could further enhance 6.97% to 8.43% oil recovery, even after HPAM flooding used. All the results revealed the EOR potential in HDAPAMs flooding.     

三次采油用聚合物驱油剂PL-2的合成与溶液性能研究

采用胶束聚合的方法合成了三次采油用聚合物PL-2,室内研究了表面活性剂的浓度、疏水单体、阴离子单体含量以及在盐水中聚合物溶液表观粘度的影响,并进一步评价了合成聚合物的抗剪切性与热稳定性。实验结果表明:疏水单体与阴离子单体含量分别在0.6%与10%时,该聚合物驱油剂PL-2具有很好的增粘效果,且抗剪切及热稳定性能优良,其性能可以满足高温、高矿化度油藏聚合物驱油的要求。     

Evaluation of hydrophobically associated polyacrylamide‐containing aqueous fluids and their potential use in petroleum recovery

Acrylamide and tridecyl acrylate copolymers were synthesized by micellar copolymerization to obtain water‐soluble, hydrophobically modified polymers. Rheological properties of the obtained polymer solutions were evaluated and compared to those of solutions of a commercial polyacrylamide currently used in the petroleum industry. The behavior of the copolymer solutions was studied as a function of the variation of hydrophobic monomer content incorporated in the copolymer as well as the salt content of the aqueous medium, for diluted and semi‐diluted regimens. Comparative studies of such effects on the intrinsic viscosity and the critical concentration of those polymers were conducted. The increase in hydrophobic monomer content produced a sudden increase in the bulk and absolute viscosity of the polymeric solutions, a trend that was more intense from a certain concentration typical for each polymer. Salt addition led to lower bulk viscosity caused by a stronger interaction among hydrophobic groups, resulting from minimized exposure of such groups and water. The same effect was observed for the critical concentration. A comparison of the synthesized polymers with industrial polyacrylamide showed that the synthesized polymers were characterized by advantageously high shear strength and high salt resistance. However, in the absence of salts, higher copolymer amounts were needed to prepare solutions whose viscosity was the same as that of commercial polyacrylamide. © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 91: 3686–3692, 2004     

High-viscoelastic graft modified chitosan hydrophobic association polymer for enhanced oil recovery

The conventional partially hydrolyzed polyacrylamide (HPAM) is greatly restricted by its single linear molecular structure in oil reservoirs with severe reservoir conditions such as high temperature and high salt. In this article, the chitosan (CS) grafted imidazoline monomer copolymer (CS-g-AM/AA/NIDA) was prepared from N-maleyl CS (N-MCS), acrylamide (AM), acrylic acid (AA), 1-(2-N-acryloylaminoethyl)-2-oleoyl imidazoline (NIDA) by free radical copolymerization. The structure was determined by means of Fourier transform infrared spectroscopy, ¹H nuclear magnetic resonance spectroscopy, scanning electron microscope, thermal gravimetric analysis, and so forth, which confirmed the successful preparation of the copolymer with good thermal stability. Under the same conditions, compared with HPAM and copolymer CS-g-AM/AA, CS-g-AM/AA/NIDA greatly increased the viscosity of the aqueous solution and exhibited excellent shear stability (viscosity retention rate 15.62, 4.91, and 11.54% at 510 s⁻¹), temperature resistance (the viscosity retention rate reached 50.89, 24.50, and 36.59% at 120°C) and salt resistance (14,000 mg/L NaCl: viscosity retention rate up to 17.27, 8.26, and 14.60%). In addition, core flooding experiments showed that oil recovery could be enhanced by up to 8.08% by CS-g-AM/AA/NIDA. As a natural polymer material, CS has hardly been reported for polymer flooding, and it is expected to replace general polymers in tertiary oil recovery.     

AM/AMPS/SMA三元共聚物的合成及其性能研究

采用自由基胶束聚合法制备了丙烯酰胺/甲基丙烯酸十八酯/2-甲基-2-丙烯酰胺基丙磺酸三元疏水缔合共聚物(HAPAM),系统研究了HAPAM水溶液的流变行为。结果表明,在聚丙烯酰胺大分子主链上引入阴离子基团和疏水基团后。阴离子的电粘效应与疏水基团的疏水缔合作用相互协同作用,使得共聚物水溶液的粘度明显提高;盐溶液对疏水缔合作用的增强效应与阴离子基团的耐盐性相互结合,使HAPAM水溶液的抗盐性能得以明显提高;HAPAM在水溶液中可以有效的形成大量疏水微区,因而具有较好的耐温耐盐和增粘性能。     

矿化度对疏水缔合聚丙烯酰胺溶液性质的影响

研究了NaCl和CaCl2对实验室自制疏水缔合聚丙烯酰胺(HAP)溶液性质的影响。结果表明,ρ(HAP)= 1000 mg/L的溶液,随着ρ(NaCl)的增加,表观黏度先降低后增加再降低,当ρ(NaCl)=3 g／L时,溶液的黏度仍有32．8 mPa·s,远大于部分水解聚丙烯酰胺(3530S型);在0．98 MPa的压力下,HAP溶液通过核微孔滤膜的能力随ρ(NaCl)的增加,逐渐降低。动态光散射实验结果表明,与NaCl相比,ρ(CaCl)=1500 mg／L的溶液对线团尺寸的影响较大,当ρ(Ca2+)=400mg/L时,溶液中聚合物线团直径达到1334 nm,比用去离子水配制溶液的线团直径要大得多。HAP溶液在盐水体系中具有较好的增黏性。     

Hydrolysis and thermal stability of partially hydrolyzed polyacrylamide in high-salinity environments

Partially hydrolyzed polyacrylamide (HPAM) is the water-soluble polymer most often used in flooding applications in the petroleum industry. However, in aqueous solutions at high temperatures, HPAM undergoes hydrolysis of the lateral amide groups, and the presence of salts in the solution can lead to precipitation of this polymer. Therefore, a method was developed to monitor the thermal stability of HPAM solutions in different saline environments and varying temperatures. The proposed test method involved measurements of intrinsic viscosity as a function of time and determination of the degree of hydrolysis of the HPAM by elemental analysis. The results obtained indicated that the presence of divalent cations (Ca⁺² and Mg⁺²) negatively influenced the intrinsic viscosity of the solutions and in some systems led to precocious precipitation of the polymer in environments with higher concentrations of these cations. The hydrolysis reaction of the amide groups to the acrylate groups of the HPAM chain was significantly affected by rising temperature: at 50 °C, hydrolysis occurred, but not as significantly as at 70, 85, 90, and 95 °C. Hydrolysis up to 84% was observed for solutions processed at 90 °C. The results also indicated limits of hardness for the brine at some temperatures: 1353 ppm for 95 °C and 2867 ppm for 70 °C. For brine containing 13,610 ppm or more of divalent cations, hydrolysis and precipitation of the polymer were not observed at 50 °C. © 2019 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2019 , 136, 47793.     

新型表面活性剂疏水缔合聚合物提高原油采收率的性能研究

介绍了渤海海上油田二元复合驱驱油的设计与开发方案,以新型表面活性剂(非离子型表面活性剂:DMES-14、TX-100)和疏水缔合聚丙烯酰胺(HAPAM)为主。二元复合驱驱油体系主要需要双子表面活性剂双十四酸乙二酯双磺酸盐型表面活性剂(DMES-14),疏水缔合聚丙烯酰胺以及取自海上油田平台的回注水。该体系同时对粘度和表面张力进行了研究。结果表明,该体系在不要求浓度的情况下可以达到超低界面张力2.48×10~(-3) m N/m,在油藏中粘度可达到55 m Pa;随后的岩心驱替试验表明,在水驱含水75%的状况下进行二元复合驱驱油效果可提高至38.6%以上。总之,该实验研究提供了非离子表面活性剂与疏水缔合水溶性聚合物驱油体系的实用信息以及可以在渤海海上油田进行大规模应用HAPAM。     

黏弹性颗粒驱油剂的制备与性能

经过长期的注水开发,我国大部分油田已面临非均质性严重、剩余油分散等现状,依靠常规方法仍有近一半原油滞留地下无法采出。线型聚丙烯酰胺驱油剂在非均质油藏中沿高渗条带窜流,扩大波及体积能力差,无法起到大幅度提高采收率的作用。对此,创新设计了一种“交联-支化共存”新型分子结构,采用自由基聚合,建立了多官能引发体系,发明了动力学调控机制,研发了结构可控的黏弹性颗粒驱油剂(B-PPG)。B-PPG在性能上兼具部分水解聚丙烯酰胺和交联聚丙烯酰胺的双重优点:它既具有线型聚丙烯酰胺的增黏能力和在地层中的运移能力,同时又具有交联聚丙烯酰胺优异的耐温抗盐、耐老化能力和调节地层渗透率的能力。以B-PPG为主剂的非均相复合驱技术已应用于胜利油田聚驱后油藏,提高采收率8.5个百分点,最终采收率高达63.6%,实现聚驱后油藏高效开发。     

A novel twin-tailed hydrophobically associating copolymer: synthesis, characterization and solution properties

Novel twin-tailed hydrophobically associating copolymers (DDSPAM) were prepared by micellar copolymerization of acrylamide (AM) and sodium vinylsulfonate with N,N-didecyl-N-methyl-N-(4-vinylbenzyl)ammonium chloride in an aqueous solution. The structure and composition of DDSPAM were characterized by ¹H-NMR and elemental analysis. While the molecular weights of the copolymers were obtained via static light scattering, the hydrodynamic radius of aggregates was investigated using dynamic light scattering. The critical micellar concentration cmc and γ _cmc values of DDSPAM were measured using fluorescence and later correlated with the values obtained from surface tension measurements. In addition, the viscosity stability studies of DDSPAM and hydrolyzed polyacrylamide (HPAM) revealed that DDSPAM, with twin tails of hydrophobic groups, exhibited better salt tolerance as well as temperature resistance compared to HPAM.     

Rheological Behaviour of Poly (Acrylamide-G-Propylene Oxide) Solutions: Effect of Hydrophobic Content,Temperature and Salt Addition

Abstract

The viscosity of hydrophobically modified polyacrylamide was investigated as a function of polymer concentration in aqueous and in salt solutions, and also as a function of temperature. The graft copolymers were constituted of polyacrylamide backbone and different amount of hydrophobic polypropylene oxide) graft chains. Measurements of intrinsic viscosities have been performed by using a Contraves low-shear LS-40 rheometer. From these results, a dependence of the intrinsic viscosity of the polymer solution with the molecular weight was observed, where an increase of the latter resulted in higher intrinsic viscosity. In this case, the effect of the molecular weight was more emphasized than the effect caused by the slightly different degrees of hydrophobic incorporation. When enhancing the temperature, it was not verified a significant change on the reduced viscosities of the copolymer solutions and the graft chain length was also observed.     

疏水性聚丙烯酰胺的合成实验研究

疏水性聚丙烯酰胺是一种重要的疏水缔合水溶性聚合物,它可以通过多种方法合成。本文结合均相共聚法和表面活性大单体法2种方法,以丙烯酸和Span80为原料首先合成了一种具有表面活性的疏水缔合型单体Span80-AA,然后将Span80一AA与丙烯酰胺聚合反应合成疏水性聚丙烯酰胺,并研究了时间、引发剂浓度、溶剂配比、大单体含量和温度对疏水聚合物粘度和分子量的影响,从而得到比较合适的实验条件。     

Hydrophobic aggregation in aqueous solutions of hydrophobically modified polyacrylamide in the vicinity of overlap concentration

The rheological behavior and hydrophobic association of hydrophobically modified polyacrylamide with 0.5 mol% of hydrophobic n-nonylacrylamide units were studied in the vicinity of the overlap concentration. It was shown that the rheological properties of aqueous polymer solutions are determined by the formation of hydrophobic domains playing a role of physical cross-links between polymer chains. It was observed that a pronounced increase of the viscosity above the overlap concentration is accompanied by the increase of the concentration of hydrophobic domains, but the average size of one domain remains constant.     

The solution behavior of hydrophobically associating zwitterionic polymer in salt water

The acrylamide‐based hydrophobically associating zwitterionic polymer was prepared, which was composed of dimethyl‐dodecyl‐allyl ammonium chloride as hydrophobic group and carboxyl betaine 2‐(4‐acrylamido‐propyl‐dimethyl ammonic)‐sodium acetate as functional group. Hydrophobically associating polyacrylamide (HAPAM) was also prepared for comparative study. The behaviors of polymers in pure water and salt solutions were investigated by the means of apparent viscosity test, laser light scattering, atomic force microscope, and fluorescence experiments. The viscosities of polymer solution increased with the increasing of salt concentration, which indicated that the addition of salt resulted in significant antipolyelectrolyte effect in the zwitterionic polymer solution. The results of dynamic laser light scattering experiment also showed that the average hydrodynamic diameters of the zwitterionic polymer molecules increased with the increasing of salt concentration. The network structures had been observed by atomic force microscope and the addition of salt strengthened the formation of network structures. The results of fluorescence experiment showed that the addition of salt could enhance the association of hyrophobically zwitterionic polymer. © 2013 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2014 , 131, 39707.     

Studies on the self‐assembly behavior of the hydrophobically associating polyacrylamide

Contrasted with partially hydrolyzed polyacrylamide (HPAM), the self‐assembly behavior and microstructure of hydrophobically associating polyacrylamide (HAPAM) in aqueous solution have been studied by means of fluorescence spectrum, transmission electron microscopy (TEM), atomic force microscope (AFM), and apparent viscosity test in this article. The fluorescent probe analysis indicates that the HAPAM molecules will form associating aggregates in pure water. The results show that HAPAM can easily self‐assemble to form an aggregate by hydrophobic driving force in dilute aqueous solution. The association of hydrophobic groups of the HAPAM causes the formation of supermolecule, so there are associating aggregates formed at very low concentration and then leads to the formation of network at a higher concentration. TEM and AFM measurements show that a distinct network structure has been formed in 1000 mg L^?1 of HAPAM solution, indicating the strong association of hydrophobic groups. These results are consistent with the viscosity measurement and reveal that the excellent viscosification of HAPAM is due to the association of hydrophobic groups in the aqueous solution. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2012     

弱碱型三元复合驱采出水的流变性变化规律

通过旋转黏度计测试黏弹性和视黏度,研究了三元(碱、表面活性剂、聚合物)复合驱采出水的流变性。结果表明,三元复合驱采出水的黏弹性可用Maxwell线性黏弹性模型描述。其视黏度和黏弹性主要取决于所含聚合物的相对分子质量和含量,并且随聚合物含量的增加而增大。低聚合物含量三元复合驱采出水的视黏度和黏弹性模量之间存在着G=1．6736μ1.8155的关系式。     

耐温抗盐丙烯酰胺系聚合物驱油剂最新研究进展

常规的丙烯酰胺聚合物在高温高盐条件下,易发生水解和热降解反应,导致溶液黏度随温度和盐浓度的增加而降低,从而限制其应用。在聚合物亲水性大分子链上引入少量(摩尔分数小于2%)疏水基团可使聚合物的溶液呈现出特殊的流变性能,从而具有良好的耐温耐盐性能。该文综述了近几年来不同单体单元组成的耐温抗盐型水溶性丙烯酰胺系列聚合物的研究进展,并对耐温抗盐交联聚合物尤其是弱凝胶驱油体系的成胶、调驱机理以及研究状况做了简要论述。     

油田采出水聚丙烯酰胺的耐盐增粘研究

探讨了无机盐溶液中阴、阳离子对聚丙烯酰胺 (PAM)溶液粘度的影响 ,确定了影响 PAM溶液粘度的主要因素是二阶阳离子 (如 Ca2 + 及 Mg2 + 离子 ) ,研究 PAM在高矿化度油田采出水中加入增粘稳定剂以保持 PAM在油田采出水中的粘度 ,满足回注水的要求     

Statistical and rheological evaluation of the effect of salts in partially hydrolyzed polyacrylamide solutions

Partially hydrolyzed polyacrylamide (PHPA) is the most common anionic copolymer used in Enhanced oil recovery (EOR), but the use of this polymer presents some limitations in the presence of divalent cations. The objective of this work was to evaluate the thermal stability of PHPA in brines containing Na⁺, Mg²⁺, and Ca²⁺ cations (isolated or combined). In this study, the PHPA used at a concentration of 2500 mgL⁻¹ has a MW of 20 × 10⁶ Da. The stability of the polymeric solutions was monitored through rheological analyses for 180 days at 70°C, in the absence of oxygen, using a central composite rotational design. In the absence of dissolved oxygen and cations, the PHPA solution was basically the same as that observed over a period of 30 days. It was observed that Ca⁺² ion had the greatest influence on reducing the viscosity of PHPA in all cases. Polymeric solutions with Total dissolved solids (TDS) greater than 1000 mg L⁻¹ showed complete degradation of the polymer in 180 days. The statistical data corroborate the rheological results, showing that only the main effect of Na⁺ was not statistically significant and that the concentrations of Mg²⁺ and Ca²⁺ presented statistically significant effects in their linear components and quadratic components.