Polymers for enhanced oil recovery: A paradigm for structure–property relationship in aqueous solution

Recent developments in the field of water-soluble polymers aimed at enhancing the aqueous solution viscosity are reviewed. Classic and novel associating water-soluble polymers for enhanced oil recovery (EOR) applications are discussed along with their limitations. Particular emphasis is placed on the structure–property correlations and the synthetic methods. The observed rheological properties are conceptually linked to the polymer chemical structure (1) and topology (2). In addition, the influence of external parameters, e.g. temperature, pH, salt, and surfactant, on the rheological behavior is reviewed. Progress booked in deeper understanding of the structure–property relationship is thoroughly discussed. Furthermore, a critical overview of the synthetic methods as well as of the solution properties of these polymers is provided. In this respect the influence of “internal” (i.e. chemical structure) and “external” (vide supra) factors on these properties provide a conceptual toolbox for the rationalization of the response of water-soluble polymers to external stimuli. In turn, such rationalization constitutes the basis for the design of new polymeric structures for EOR applications.     

疏水缔合水溶性丙烯酰胺—丙烯酸正辛酯共聚物的溶液性能

采用自由基胶束共聚法制备了水溶性的丙烯酰胺丙烯酸正辛酯疏水缔合共聚物。研究了共聚物水溶液的性能及其影响因素。随疏水基团含量增加，共聚物在水中的特性粘数［η］减小，代表分子线团间流体力学相互作用的Ｈｕｇｇｉｎｓ常数ＫＨ增大。随共聚物浓度增加，在临界缔合浓度Ｃ以上，分子间缔合大量形成，水溶液表观粘度急剧增加。     

Carbon-13 n.m.r. study of end-groups in polymers prepared using azoisobutyronitrile as radical initiator

¹³C-azoisobutyronitrile has been used to initiate polymerizations of methyl methacrylate and styrene. The n.m.r. spectra of the resulting polymers show peaks arising from the combined initiator fragments with chemical shifts dependent on the nature of the adjacent monomer unit.     

The effects of charge densities on the associative properties of a pH-responsive hydrophobically modified sulfobetaine/sulfur dioxide terpolymer

Sulfur dioxide, zwitterionic monomer, 3-(N,N-diallylammonio)propanesulfonate and a hydrophobic monomer N,N-diallyl-N-octadecylammonium chloride were cycloterpolymerized in dimethyl sulfoxide using azobisisobutyronitrile (AIBN) as the initiator to afford water-insoluble polysulfobetaines (PSB) in excellent yields. The PSBs were converted into the corresponding anionic polyelectrolyte (APE) by treatment with 1 equiv. of sodium hydroxide. Treating the pH-responsive PSB polymers with different equivalents of NaOH varied the zwitterionic and anionic charge densities in the polymer chain. The polymer chains with zwitterionic fraction greater than 0.5 were found to be insoluble in water. The solution properties of the APE and PSB/APE systems containing varying amount of the hydrophobic monomers in the range 0-10 mol% were investigated by viscometric techniques. It was found that PSB/APE polymer with a ratio of 33:67 for the zwitterionic and anionic fractions in the polymer chains, respectively, gave the highest viscosity value. The polymer concentration (C*_HA) of around 1 g/dl was required for the manifestation of significant hydrophobic associations. The polymer solutions exhibited sharp increase in viscosity with increasing polymer concentrations in salt (NaCl)-free as well as salt-added solutions. The presence of sodium chloride is shown to enhance intermolecular associations in polymers having hydrophobes in the lower mol% range, whereas, intramolecular associations were manifested in polymers containing higher proportions of the hydrophobes.     

耐温抗盐共聚物AMPS／AM／AMC14S的合成

用引发聚合方法合成了ＡＭＰＳ／ ＡＭ／ ＡＭＣ１４Ｓ 三元共聚物。研究结果表明,在单体总浓度１０ ％ —１５ ％ ,ＡＭＣ１４Ｓ浓度０ ．１５ ％ ,ｐＨ值为中性时,在３０—４０℃反应８ ｈ 可以得到转化率９７％ 、特性粘数１０ —１７ ｄＬ／ｇ 的共聚物。通过红外光谱研究了共聚物的分子结构,并通过差热分析研究了共聚物的耐热性。     

端羟基改性超支化聚酯的热稳定性及分解行为

采用热失重方法(TG)研究了端羟基超支化聚酯和端羟基改性超支化聚酯在氮气气氛中的热稳定性及分解行为。端羟基超支化聚酯的热分解过程包括酯基降解和碳碳键断裂2个阶段,随着代数增加,热稳定性有所改善。当端羟基被烷烃链取代后,端羟基超支化聚酯的热分解温度大幅度提高。低代数端羟基改性超支化聚酯的分解以碳碳键断裂为主,高代数热分解仍包括酯基降解和碳碳键断裂2个阶段。端羟基改性超支化聚酯的表观分解活化能明显提高。     

大庆油田疏水缔合聚合物驱物理实验模拟

通过阻力系数(FR)和残余阻力系数(FRR)测定及岩心驱油实验,在实验室考察了一种疏水缔合聚合物HAP工业产品在大庆油田条件下(45℃,天然或模拟人造岩心)的驱油性能,并与一种HPAM工业产品(M=1.43×107,HD=27%)进行了对比.HAP溶液用矿化度4 456 mg/L的污水配制,HPAM溶液用矿化度918 mg/L的清水配制.800 mg/L HAP溶液流过水测渗透率0.037-0.333 μm2的天然岩心时产生的FR＞10,FRR＞2.在三层非均质人造岩心(Vk=0.72, Ka=0.840-1.120 μm2)上进行的岩心驱油实验中,相同浓度(1 000 mg/L)HAP溶液驱替水驱残余油的采收率比HPAM溶液高3%-4%(OOIP),相同粘度(41-42 mPa·     

The Study of Vascular Prostheses Aging by Infrared

The Fourier transform infrared (FTIR) spectrum of polyethylene terephthalate (PET) fibers extracted from vascular prostheses was used to illustrate the mechanisms of structure degradation. A quantitative model for fitting infrared spectra of PET samples over the region from 3200 to 3600 cm^?1 has been evaluated. Examination of a series spectrum of PET vascular prostheses collected after aging showed significant chemical differences in comparison with the virgin prosthesis. Analysis of these spectrums showed an increase of the end group concentrations for the explants. We used a complementary technique, the chemical titration method, in order to validate (FTIR) results. A considerable loss of macromolecular weight was observed, which is related to the formation of the smaller molecules that may proceed by random scission. Even if the time clearly influences the level of degradation, the results highlight other mechanisms of degradation that are probably related to human metabolism.     

Synthesis and self-assembling properties of α,ω-hydroxy-poly(ethylene oxide) end-capped with 1-isocyanato-3-pentadecylcyclohexane

A novel hydrophobic compound, 1-isocyanato-3-pentadecylcyclohexane (PDC) issued from a renewable resource material (Cashew Nut Shell Liquid), is used to end-cap poly(ethylene oxide) (PEO) of different molecular weights. The synthesis, characterization and self-assembling properties of these new associating polymers are reported. In aqueous solution, PDC modified PEOs self-associate into micellar structures which are characterized by neutron scattering. Using a star-polymer model with sticky hard sphere interactions, it is shown that the characteristics of the micelles mainly depend on the size of the PEO chain. In the case of PDC stickers, the aggregation number decreases from 25 to 17 with increasing molecular weight of PEO, from 10 to 20 kg/mol, respectively. The temperature directly impacts the interaction potential between the hydrophilic coronas of PEO which become less repulsive with increasing temperature. Rheological measurements, performed in dilute solution, clearly demonstrate that PEO micelles self-associate into open supramolecular structures. The correlation length of these loose clusters increases with polymer concentration and the hierarchical self-assembly follows the rules of the percolation theory. The sol/gel transition takes place at the overlap concentration of clusters. In semi-dilute solution, the viscoelastic properties of PDC end-capped PEOs are well described by the Maxwell model with a single relaxation mode. The characteristic time of the network follows an Arrhenius temperature dependence with an activation energy of 70 kJ/mol, in very good agreement with the size of PDC stickers.