【作者】 董喜贵；

【导师】 俞庆森； 李凤林；

【作者基本信息】 浙江大学 ， 物理化学， 2005， 博士

【摘要】 深入分子水平探索复杂石油系统的一些共性和本质问题,为发展采油新技术提供理论基础,是石油和化学等多个学科日益关注的重要课题,是一个理论联系实际的研究领域。石油由极性自强到弱的沥青质、胶质、烃类（包括烷烃、环烷烃和芳香烃）构成,是一种特殊的胶体分散系统。以沥青质为核心的石油分散系统的稳定性问题,包括沥青质的聚集稳定性,界面稳定性,热稳定性等,是贯穿于石油勘探、开采、运输与加工全过程的重要问题,研究该问题对石油科技和工程具有理论和现实指导意义。本文就是围绕石油系统的稳定性问题,采用从实验和理论两个方面将理论联系实际,着重开展沥青质的相关性质研究和复合驱配方优化的研究。主要研究内容和成果有: 探讨了石油沥青质及胶质的组成和结构。分离提取了国内外7种原油的正己烷沥青质,通过¹H和¹³C核磁共振（NMR）测定,结合元素分析、分子量测定,计算平均分子式和结构参数,推测模型分子。沥青质和胶质的基本结构单元均可以用稠环芳烃连接环烷烃和烷基侧链并含杂原子的单元来表示,不同沥青质及胶质的母体结构基本相似,结构单元之间形成缔合体,沥青质的缔合数约为3～6,胶质的缔合数约为2。模型分子为沥青质和胶质提供了形象、直观、简化的化学结构,有助于从分子水平加深对它们的认识和研究,同时也证明NMR是研究沥青质等复杂组分平均结构的一种较好方法。 考察了沥青质及胶质的热稳定性。采用热重分析（TG/DTG）直接观察沥青质及胶质的热裂解过程。实验结果表明,沥青质和胶质的热裂解失重温度范围明显不同,沥青质耐热稳定性强,主裂解范围窄、温度高,胶质裂解范围宽。热裂解特征与我们依据NMR推测的模型分子的结构特征相吻合。比较了三种不同的热裂解动力学处理方法,结果表明,对于组成复杂的沥青质及胶质,不宜简单地采用单个反应机理来进行热裂解动力学计算。我们把活化能分布模型（DAEM）引入沥青质的热裂解动力学处理,获得了活化能和指前因子的分布函数,结果满意。同时,观察到指前因子与活化能之间都存在明显的补偿效应,并可从过渡态理论以及我们推测的模型分子结构特征加以解释。 探索了沥青质及胶质的溶液稳定性。以大庆沥青质或胶质—甲苯溶液为对象,采用紫外—可见和荧光等光谱技术,从吸收强度、吸光系数、吸收峰变迁、极大峰位置、总荧光强度和相对峰强度等角度探讨沥青质或胶质在溶液中的聚集稳定性。实验证明,沥青质和胶质均含有一定的发色团和荧光团,在甲苯稀溶液中也会发生聚集,大庆沥青质浓度达到100mg·L^-1左右聚集程度最大,胶质浓度更多还原

【Abstract】 It is an increasingly important subject for petroleum and chemistry researchers to explore some general and essential aspects of the complexed petroleum system from molecular level and to present theoretical basis for the development of new techniques of oil recovery. It is well-known that crude oil can be considered to be a special colloidal dispersion system of alsphaltenes and resins, which constitute the discrete and polar components, dispersed in a continuous phase made of non-polar compounds, paraffins, naphthenes and aromatics. Asphaltene acts as the core of an asphaltene micelle. Resins act as peptizing agents keeping asphaltenes in suspension and maintaining the stability of crude oil. The stability related asphaltene precipitation, interfacial interaction, and thermal cracking runs through the whole process of petroleum industry and its study may take directive effects on the theory and practice of petroleum science and engineering. In the present work, some advanced theoretical methods and instrumental techniques are used to study on the structural stabilities particularly related to asphaltenes and on the optimization of recipe of combined flooding. The main contents and results are as follows.Firstly, the composition and structure of petroleum asphaltenes and resins are investigated. ¹H and ¹³C NMR spectra of seven kinds of petroleum asphaltenes separated from different crude oils with n-hexane as solvent are determined with a Bruker Avance DMX500 NMR spectrometer. A series of average chemical structural parameters are obtained on the basis of the ¹H and ¹³C NMR information. By combining the experimental relative molecular weight and the elemental analysis results, the average molecular formula of the asphaltene and resin unit sheets are calculated and the hypothetical model molecules are evaluated. It can be found that the asphaltene or resin units are mainly composed of the polycyclic aromatics linked with naphthalene rings and side aliphatic chains. There obviously exist heteroatoms, O, N and S, in the asphaltene or resin units. The units can be associated each other with the association number from 3 to 6 for asphaltenes and that of about 2 for resin. These results provided an efficient structural description for the study of petroleum asphaltenes and resins at the molecular level. It is also tested that NMR is a good method to study the average structure of a complexed system such as asphaltenes.Secondly, the thermal stabilities of asphaltenes and resins are carried out.. Thermal pyrolysis kinetics of the asphaltenes and resins has been measured usingthermogravimetric analysis （TGA） with three or four different heating rates. It is clearly observed that there are different temperature ranges of weight losses between asphaltenes and resins. The pyrolysis process of the asphaltenes mainly occurs at a narrow temperature range with only single weight loss peak and that of the resins, however, occurs at a wide temperature range with two-peak weight loss feature. The pyrolysis stages of the asphaltenes and resins can be reasonablely explained by the model molecule assumptions from NMR measurements. Three different kinetic methods are used to quantitatively treat the TGA data. Two methods, overall first-order reaction method and two-stage first-order reaction method, are both not very well to interpret the characteristics of pyrolysis processes. A new distributed activation energy model （DAEM） is introduced to correlate the experimental TGA data. The kinetic parameters, active energy （E） and preexponential factor （ko）, of thermal pyrolysis for asphaltenes or resins at different conversion levels are calculated. It follows that many parallel reactions with different rate parameters occur simultaneously during the thermal pyrolysis of asphaltenes or resins. The distribution functions, fiJE) and ko（E）, are then estimated by DAEM satisfactorily. The compensation effect is clearly observed from a straight line of the plot of ln(（Ao） versus E, which is discussed from the transition state theory combining with the hypothetical model molecules.Thirdly, the stability of asphaltenes and resins in solutions is discussed. Evidence of the aggregation behavior of asphaltene-toluene and resin-toluene solutions is investigated by UV-vis and fluorescence spectroscopy. The stability and aggregation tendency are discussed from various experimental results such as absorbance, absorptivity, florescence peak position, fluorescence peak shift, and total florescence intensity. Similar absorption spectra and fluorescence spectra for the asphaltenes and resins in toluene are observed due to the similar type of chromospheres and fluorophores. The experiments allow concluding that asphaltenes or resins in toluene solutions start to aggregates at considerably low dilution. The aggregation appears at higher concentration values as lOOmg/L for Daqing asphaltenes and at at lower concentration values as 40mg/L for Daqing resins. Therefore, the effects from the aggregation of asphaltenes or resins in solutions on the stability of crude oil usually should be considered.In chapter 5, the interfacial stability of the alkaline-surfactant-polymer （ASP） system is studied. With the crude oil from No. 2 Oil Production Company, Daqing Oil Field Co. Ltd as the object, the interfacial tensions between oil and water for manyalkaline-surfactant-polymer systems with different compositions are determined. The effects of the addition of polar compounds on the values of the interfacial tension are investigated. It follows that the ultra low interfacial tension can be obtained only when a surfactant is selected with appropriate molecular chain length and that obvious influences of polar compounds on the interfacial tension can be observed. Combining the principles of phase equilibrium and chemical equilibrium with the theory of surface thermodynamics, a simple model is abstracted from the complexed crude oil-alkali liquor-surfactant system and then a quantitative expression is proposed. From the model, the effects of the concentrations of petroleum acid, alkaline, and surfactant on the production of interfacial active acidic anion and the form of ultra low interfacial tension are explained. The surface thermodynamic model can correlate the interfacial tension values with results in reasonable agreement with the observed data. It can effectively express, to a certain extent, the tendency of interfacial tensionchange for the ASP combined flooding systems.In chapter 6, the prescription of ASP combined flooding are designed and optimized. With Nan’erxi polymer flooding of industrial scale area in Daqing oilfield as the object, several main factors, including interfacial tension between oil and water, stability of the combined system, adsorption of chemicals, recovery of physical simulation flooding experiment, etc. are evaluated to screen out the suitable chemicals, the prescription of combined system and the separate injection projects for polymer and alkaline-surfactant system. Both the selected alkaline-surfactant （AS） system and the ASP system can achieve allowable interfacial tension in a wide alkaline and surfactant concentration range and have good interfacial tension stability for a long time. Physical simulation flooding experiments indicates that the method of separate injection of polymer and alkaline-surfactant system has higher recovery enhance rate than only polymer flooding. The method of separate injection can enhance oil recovery about 5 percent above the usual polymer flooding. This new method needs no more construction than the usual ASP flooding and can make use of sewage well at the same time. Therefore, a considerable economy benefit can be obtained.更多还原