油气开采用疏水缔合聚合物的研究

【作者】 韩利娟；

【导师】 罗平亚；

【作者基本信息】 西南石油学院 ， 油气田开发工程， 2004， 博士

【摘要】 三次采油是提高原油采收率最重要的步骤，对于我国注水开发油田提高石油采收率的方法主要为化学驱。目前我国化学驱研究中，聚合物驱技术相对较为成熟，但聚合物驱油效果和效益还需进一步改进和提高。目前常用的聚合物包括以部分水解聚丙烯酰胺(HPAM)为代表的合成聚合物和以黄原胶(Xanthan Gum)为代表的生物聚合物在用于高温高盐油藏时都存在难以克服的问题。因此，近年来，耐温耐盐聚合物的研制已成油气开采用聚合物迫切需要解决的问题，而疏水缔合水溶性聚合物(HAWSP)由于具有不同于一般水溶性聚合物的特殊流变性，一直受到科学工作者极大的关注。 疏水缔合聚合物分子链上含有少量疏水基团，当疏水缔合聚合物溶于水时，由于疏水基团之间的缔合作用而形成超分子聚集体，从而形成可逆的网络结构，溶液粘度显著提高，使疏水缔合聚合物表现出不同于一般水溶性聚合物的特殊流变性。因此，疏水缔合聚合物能在一定程度上克服油气开采中常用的聚丙烯酰胺耐温耐盐性差和易剪切降解的缺陷，成为一种具有良好应用前景的油气开采用水溶性聚合物材料。尽管如此，目前国内外研究开发的疏水缔合聚合物在耐温抗盐和稳定性等方面还存在一定的问题，聚合物的性能还有待进一步改进。 为了更好地设计出具有特定性能的疏水缔合水溶性聚合物，有必要研究其在溶液中的存在状态、缔合机理、缔合结构的形状及影响缔合的因素，找到直观的科学依据来阐释缔合聚合物在溶液中的缔合机理，真正弄清HAWSP具有特殊流变性的原因，从而为疏水缔合聚合物的分子设计和应用提供可靠的依据。因此，本文的研究内容包括三个方面：一是采用荧光光谱、紫外光谱和透射电镜等手段研究HAWSP在水溶液中的聚集和网络结构的形成来研究疏水缔合聚合物的缔合机理；二是在此基础上探索提高疏水缔合聚合物耐温抗盐性的途径；三是根据疏水缔合聚合物的结构特征，结合实验研究结果，计算疏水缔合聚合物溶液临界浓度，并对溶液浓度区域进行划分。 ·疏水缔合聚合物的缔合机理的研究 以芘为探针用荧光光谱法和紫外光谱法研究了疏水缔合聚合物在溶液中的缔合状态及网络结构的形成过程，得出疏水缔合聚合物在溶液中的缔合机理。通过粘度法证实当溶液中有大量疏水微区生成时，疏水缔合聚合物溶液粘度出现急剧增大。 在使用透射电镜研究疏水缔合聚合物和聚丙烯酰胺溶液的微观结构时发现，聚丙烯酰胺和疏水缔合聚合物在一定浓度时都可以形成网络结构，且从TEM照片来看，聚丙烯酰胺在溶液中形成的网络结构与疏水缔合聚合物在溶液中形成的网络结构在表面上没有多大差别。 为了更好的了解疏水缔合聚合物的溶液性质与结构之间的关系，使用相分离模型研究了疏水缔合聚合物在溶液中的缔合作用能。实验结果表明，疏水缔合能比化学键的键能小，然而却比范德华力和氢键的键能大，这就从分子间相互作用力的角度解释了疏水缔合聚合物比一般水溶性聚合物具有更高增粘能力的原因。 探索提高疏水缔合聚合物耐温抗盐性的途径 鉴于目前所研究的疏水缔合聚合物大多为长链梳形结构，尽管在高效增粘方面效果显著，然而在耐温、抗盐和稳定性等方面却存在一定问题。为了提高聚合物驱对高温高盐等油藏的适应性、扩大聚合物驱适用范围，必须加深耐温耐盐聚合物的基础研究。在弄清楚疏水缔合聚合物的缔合机理的基础上，根据分子间相互作用的物理模型，首先探索对长链梳形疏水缔合聚合物进行改性，将梳形缔合聚合物通过适当的交联，生成可溶性体型高分子即类星型结构的缔合聚合物，并对其溶液的流变性和稳定性进行了研究。在研究了类星型结构的缔合聚合物的基础上，研究了星型缔合聚合物在各种盐浓度下的流变行为。实验结果表明类星型结构的缔合聚合物和星型缔合聚合物具有一定的耐温抗盐性。 疏水缔合聚合物溶液临界浓度的计算和浓度区域的划分 前面的研究可以发现，疏水缔合聚合物溶液网络结构的形成会导致溶液粘度的突变。溶液粘度发生突变的临界浓度尽管可以通过荧光光谱法、紫外光谱法和粘度法等手段获得，但通过模型设计、建立数学模型来计算聚合物溶液的临界浓度对聚合物的分子设计及应用具有重要的指导意义。 由于疏水缔合聚合物在极稀溶液中即可通过分子间的相互缔合形成超分子聚集体，因此，为了更好的了解疏水缔合聚合物在各个浓度区域的形态和性质，根据疏水缔合聚合物的结构特征，结合实验研究结果，对疏水缔合聚合物溶液浓度区域作了划分。将疏水缔合聚合物溶液分为极稀溶液、稀溶液、亚浓溶液和浓溶液。关键词:疏水缔合聚合物，荧光光谱，紫外光谱，缔合，临界浓度，透射电镜，溶液 结构，缔合作用能，星型缔合聚合物，流变性，耐温抗盐更多还原

【Abstract】 Enhanced oil recovery (called tertiary oil recovery in the past) processes have as their objective the increase of recovery from reservoirs depleted by conventional recovery, i.e. by primary recovery with natural production mechanisms or by secondary recovery with water-flooding or gas injection. Enhanced oil recovery techniques can be subdivided into three categories: thermal, miscible and chemical. In our country, chemical process is the main technique to enhance oil recovery. Up to now, polymer flooding has succeeded in many oil fields, but both the effectiveness and efficiency of oil recovery need further promoting. Because the most application polymers, such as partially hydrolyzed polyacrylamide and xanthan gum, have met some problems when used in high temperature or high salinity reservoirs. So the developments of new class of polymers, which have the ability of both temperature endurance and salt resistance, become very urgent. Hydrophobically associating water-soluble polymers (HAWSP) for which exhibit special rheological properties different from that of conventional polymers have recently received considerable attention.HAWSP is a kind of water soluble polymer, containing a few hydrophobic groups on the side chains, usually less than 2mol%. Owing to hydrophobic effect, when polymer dissolved in water, some of hydrophobic groups may associate with each other, form super-molecular aggregates, and even transitional network structure, which induces a substantial increase in solution viscosity. So, to some extent, HAWSP can overcome the deficiency of conventional polymers in sensitivity to temperature, ionic strength and shear. Although HAWSP have been studied for many years and the performance of HAWSP is indeed better than that of conventional polymer, the performances of HAWSP in temperature endurance, salt resistance and stabilities need further improving.In order to get the HAWSP with required performances, it is necessary to know its association mechanism in aqueous solution, influencing factors, etc. The confirmation of association mechanism and solution microstructure of HAWSP will help to know the reason why hydrophobic associating polymer has unusual rheological behavior and allow us establish the relationships between polymer architecture and macroscopic properties, and so permit the tailoring of the molecule structure for specific application. So the main tasks of this dissertation are: first of all, study the associating mechanism of HAWSP by fluorescence spectrum, ultraviolet spectrum and transmission electron microscope; then, seek for a method to improve the performances of HAWSP in temperature endurance or salts resistance; thirdly, based on the structure characteristic of HAWSP and the results of the experiments, calculate the critical concentration of HAWSP through model design and the establishment of mathematical model, and put forward the partition of solution regimes of HAWSP. Study of association mechanism of HAWSPFluorescence spectrum and ultraviolet spectrum using pyrene as probe were used to investigate the associating status and the course of the formation of network. The associating mechanism of HAWSP in aqueous solution was deduced: in aqueous solution, with the increase of concentration, HAWSP molecule will associate with each other; then intermolecular associating of HAWSP leads to formation super-molecular aggregates; in the end, a space network structure forms. It was verified by Rheometer that the viscosity of HAWSP solution increased sharply at the concentration when a space network had formed in solution.The microstructures of PAM and HAWSP were investigated by TEM. But both PAM and HAWSP can form network in dilute solution, and it is hardly to distinguish the differences between PAM and HAWSP from the TEM picturesTo make a further understand of the relationship between solution properties and structures, phase separation model was used to investigate the association energy of HAWSP in aqueous solution. Results showed that hydrophobic association energy was smaller than the更多还原