梳形聚合物对沥青质聚集行为和稠油高压流变性质的影响

发布时间：2018-09-08 21:39

【摘要】：沥青质的稠环芳香结构及复杂的组装聚集方式使其容易聚集沉积,从而使稠油表现为高粘、流动性低的特点,这一特点使得稠油无论在开采还是运输过程中都面临巨大的挑战。向原油体系加入化学分散剂是改善沥青质的聚集状态和提高油品流动性的一种经济可行的方法。开发针对稠油中沥青质聚集体的分散剂,应首先从分散剂与沥青质间的作用力形式和强弱角度判断哪种结构的分散剂对沥青质的分散稳定性和聚集行为有更好的改善效果。因此,本课题首先考察了 MAC和PMV两组梳形聚合物对低浓度模型油中沥青质的分散效果及其聚集行为的影响,其次,研究了温度、压力及高压CO_2对脱气稠油的流变学特性的影响,特别是梳形聚合物与高压CO_2的共同作用效果。本文以自由基聚合方法合成了聚(马来酸酐-醋酸乙烯酯)(PMV)中间体,并通过侧链胺化改性制备了两个系列的梳形聚合物:一类是接枝了不同链长的链烷烃的PMV-8、PMV-14和PMV-18系列;另一类是接枝了苯胺、萘胺和2-氨基苯并咪唑的PMV-A、PMV-N和PMV-B系列。利用1HNMR表征了新型梳形聚合物的结构和接枝率。在室温及常压下,运用紫外-可见吸收光谱、浊度测量、激光动态光散射(DLS)和荧光显微镜分别探究了 MAC和PMV两组梳形聚合物对沥青质的分散稳定性(初始沉淀点)和聚集行为的影响。结果显示,MAC系列中以接枝萘环的NMAC对沥青质初始沉淀点的延迟效果最佳,使正庚烷体积分率增加22%;而PMV系列中以PMV-18的效果较佳,使正庚烷体积分率增加10%;显微镜观察沥青质的聚集由原来絮状沉淀并层层堆积的方式向更加分散的粘连态凝胶颗粒转变。通过DLS测试溶液中析出沥青质的粒径分布,发现几种梳形聚合物添加剂均能使沥青质聚集体的平均粒径降低为原来的一半且分布变窄,说明了几种梳形聚合物对沥青质颗粒具有稳定和分散效果。利用旋转流变仪的高压测试系统,考察了温度、静压力和高压CO_2对脱气(脱水、脱轻组分)稠油流变性质的影响规律。温度的升高可显著降低脱气稠油的零切复粘度,而静压力使稠油的粘度缓慢单调增加;高压CO_2可以促使稠油的复粘度显著降低,且在达到超临界压力前,其凝胶点对应的模量不变,而只与剪切角频率有关;而在超临界区,压力促使凝胶点的模量迅速降低,并使稠油向接近流体性质的方向转变。通过测试梳形聚合物与高压CO_2的共同降粘效果,其降粘幅度大于单纯的高压C02的效果,使其在7MPa CO_2压力下的复粘度比常压下降低了两个数量级,这为聚合物分散剂辅助CO_2驱的可行性提供了基础试验研究。
[Abstract]:The dense ring aromatic structure of asphaltene and the complex assembly and aggregation mode make it easy to accumulate and deposit, which makes heavy oil show the characteristics of high viscosity and low fluidity, which makes heavy oil face great challenges in both exploitation and transportation. Adding chemical dispersant to crude oil system is an economical and feasible method to improve the aggregate state of asphaltene and increase the flowability of oil. In order to develop a dispersant for asphaltene aggregates in heavy oil, it is necessary to judge which kind of dispersant has a better effect on the stability and aggregation of asphaltene from the angle of the force between dispersant and asphaltene. Therefore, the effects of MAC and PMV on the dispersion and aggregation behavior of asphaltene in low concentration model oil were investigated firstly, and then the temperature was studied. The influence of pressure and high pressure CO_2 on rheological properties of degassing heavy oil, especially the effect of comb-like polymer and high pressure CO_2. In this paper, poly (maleic anhydride-vinyl acetate) (PMV) intermediates were synthesized by free radical polymerization. Two series of comb polymers were prepared by side chain amination modification: one is PMV-8,PMV-14 and PMV-18 series grafted with alkanes of different chain lengths; The other is the PMV-A,PMV-N and PMV-B series grafted with aniline, naphthylamine and 2-aminobenzimidazole. The structure and graft rate of the new comb polymer were characterized by 1HNMR. At room temperature and atmospheric pressure, using UV-Vis absorption spectrum, turbidity measurement, The effects of MAC and PMV on the dispersion stability (initial precipitation point) and aggregation behavior of asphaltene were investigated by laser dynamic light scattering (DLS) and fluorescence microscopy respectively. The results show that NMAC with grafted naphthalene ring has the best delay effect on the initial precipitation point of asphaltene, and the volume fraction of n-heptane is increased by 22%, while the effect of PMV-18 is better in the PMV series. The volume fraction of n-heptane was increased by 10 and the aggregation of asphaltene was observed by microscope. The particle size distribution of asphaltene precipitated in the solution was measured by DLS. It was found that several comb polymer additives could reduce the average particle size of asphaltene aggregates to half of the original size and narrow the distribution of asphaltene aggregates. The stability and dispersion effect of several comb polymers on asphaltene particles are explained. The effects of temperature, static pressure and high pressure CO_2 on the rheological properties of heavy oil were investigated by using the high pressure measuring system of rotary rheometer. The increase of temperature can significantly reduce the zero-shear complex viscosity of degassing heavy oil, while the static pressure can make the viscosity of heavy oil increase slowly and monotonously, and high pressure CO_2 can make the complex viscosity of heavy oil decrease significantly, and before reaching supercritical pressure, In the supercritical region, the modulus of the gel point decreases rapidly and the viscous oil changes to the direction close to the fluid property, but the corresponding modulus of the gel point is invariant, but only depends on the shear angular frequency of the gel point, while in the supercritical region, the pressure causes the modulus of the gel point to decrease rapidly. By testing the joint viscosity reduction effect of comb-shaped polymer and high-pressure CO_2, the viscosity reduction range of comb-shaped polymer is larger than that of pure high-pressure C02, and the complex viscosity of comb polymer under 7MPa CO_2 pressure is reduced by two orders of magnitude than that under normal pressure. This provides a basic experimental study for the feasibility of polymer dispersant assisted CO_2 flooding.
【学位授予单位】：华东理工大学
【学位级别】：硕士
【学位授予年份】：2017
【分类号】：TE621

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