非氟CO2增稠剂的设计、合成及作用机理

Carbon dioxide (CO2) flooding can not only effectively enhances oil recovery but also considerably reduces greenhouse gas emissions. The low viscosity of CO2, however, leads to viscous fingering in the oil reservoirs, which in turn leads to early CO2 breakthrough and depressed oil production rates. The development of a CO2 thickener that could change the CO2 viscosity would have profound effects on oil recovery and is worth pursuing. However, the fluorous thickeners are not suitable for viscosifying CO2 in the oilfield applications because they are expensive and can cause some serious environmental issues. In this project, molecular dynamics combined with controllable polymerization will be applied to design and synthesize polyvinyl acetate, polyvinyl ethylether, amorphous polylactic acid and their copolymers with low molecular weight, which will then be used as CO2-philic segments for the design and synthesis of non-fluorous and CO2-soluble ionic and block copolymer surfactants with clear structure. Non-fluorous CO2 thickener will be selected from these surfactants. Molecular dynamics combined with high pressure small angle X-ray scattering of synchrotron radiation, high pressure dynamic light scattering and high pressure small-angle neutron scattering will be applied to investigate the self-assembly of the CO2 thickener molecules, the aggregation and size of the micelles. The viscosity of CO2 added the thickener will be measured by using high pressure rheometer. The relationship between the ability of the thickener to enhance the viscosity of CO2 and the micelles structure will be constructed, and the viscosify mechanism will be clarified. The results may get the design principles for design of the non-fluorous CO2 thickener.

CO2驱油提高石油采收率技术可实现CO2减排和利用的双赢。但CO2粘度低，极易造成其在油藏中的粘性指进，导致石油采收率降低。使用CO2增稠剂，可有效改变这一状况。含氟CO2增稠剂由于价格昂贵，对环境有害，无法获得实际应用。本项目计划采用分子动力学模拟结合可控聚合，设计、合成低分子量聚醋酸乙烯酯(PVAc)、聚乙烯基醚(PVEE)和无规聚乳酸(PLA)等亲CO2的均聚或共聚物链段，并以其为基体设计、合成可溶于CO2、结构明确的离子型和嵌段共聚物型表面活性剂作为非氟CO2增稠剂；采用分子模拟结合同步辐射高压小角X射线散射、高压动态光散射和高压小角中子散射等表征手段，研究增稠剂分子在高压CO2中的自组装行为、聚集态胶束结构和尺寸；通过高压流变仪测试增稠剂的增稠效果，关联其与增稠剂分子在CO2中胶束结构的关系，阐明增稠剂作用机理。研究结果可为非氟CO2增稠剂的分子结构设计提供参考依据。

CO2驱油提高石油采收率技术可实现CO2减排和利用的双赢。但CO2黏度低，极易造成其在油藏中的粘性指进，导致石油采收率降低。使用CO2增稠剂，提高CO2黏度，可有效改变这一状况。.本项目针对绿色、非氟CO2增稠剂的设计和应用，首先开发了用于高压浊点测试、高压乳化和高压粘度测试的三套实验装置，分别用于表征聚合物在高压CO2中的溶解性能，增稠表面活性剂构建CO2/水乳液稳定性以及CO2增稠体系的黏度；采用量子力学从头算、分子动力学等多尺度分子模拟手段结合实验，研究了拓扑结构聚醋酸乙烯酯（PVAc）、PVAc-马来酸酯共聚物、聚醋酸乙烯酯-乙烯基醚共聚物等与CO2的亲和性，筛选出PVAc-马来酸二丁酯（DBM）交替共聚物、PVAc-乙烯基乙醚（VEE）无规共聚物（VEE含量为30 mol%）、PVAc-马来酸二新戊酯（DNM）和PVAc-富马酸二异丁酯（DiBF）交替共聚物等具有较好亲CO2性的聚合物链段，并研究了其与CO2相互作用，阐明了其亲CO2的作用机制；采用可逆加成断裂链转移聚合（RAFT）与原子转移自由基聚合（ATRP）等可控聚合手段，设计合成PVAc-b-PDMAEMA、PVAc-alt-PDBM-b-PDMAEMA、PVAc-b-聚乙烯吡咯烷酮（PVP）、PVDBM-b-PEG等表面活性剂，均能用于构建稳定的CO2/水乳液体系，其中CO2体积含量可高达90%，稳定时间大于48小时，并探索了表面活性剂作用机制；考察了拓扑结构PVAc对CO2的增稠作用，结果表明1 wt%的添加量可使CO2黏度提高约31 %~55 %，PVAc-b-PVP构建的CO2/水乳液黏度相对水可提高10倍。.本项目通过分子模拟研究设计非氟亲CO2聚合物，阐明其与CO2相互作用规律，完善了亲CO2聚合物设计准则，合成了在CO2中溶解性能优异的非氟亲CO2聚合物链段作为CO2增稠剂的重要组成部分。以该链段为基体，直接增稠CO2或设计合成嵌段共聚物型表面活性剂构建乳液增稠CO2，可以为CO2驱油提供新的辅助方法，提高石油采收率。另外，本项目设计合成的绿色亲CO2物质和结构作为表面活性剂、增溶剂，可提高超临界CO2的溶解能力，是拓展超临界CO2工业化应用的一种重要手段。