【作者】 徐兆明；

【导师】 王宝辉；

【作者基本信息】 东北石油大学 ， 油气田化学工程， 2010， 博士

【摘要】 三元复合驱(ASP)是20世纪80年代中期提出的三次采油新方法。它是由碱/表面活性剂/聚合物复配而成的三元复合驱油体系,具有表面活性剂和聚合物驱共同的优点,既能提高驱油效率,又能提高波及体积,并且能较大幅度地降低表面活性剂的用量,已被各大油田广泛使用,成为油田产量接替的主要措施。但随着化学驱油剂的大量应用,不可避免的给环境带来各种危害,因此有必要分析评价ASP化学剂的环境行为和污染特性,为油田的环境治理提供一定的理论基础,为三元复合驱大规模应用提供可靠的技术保证。本文通过现代分析手段,根据现有标准及环境评价方法,确定出ASP化学剂中对环境造成影响的主要特征污染物有碱(氢氧化钠)、表面活性剂(直链烷基苯磺酸盐、未磺化油)及聚丙烯酰胺(丙烯酰胺),并详细分析了它们对环境可能造成的影响与危害,结果表明,三元复合驱中碱和未磺化油具有很大的污染特性,且呈现持久和难处理的特点;表面活性剂毒性与其浓度和结构有关;聚丙烯酰胺本身对动植物无毒性,对环境产生的影响也很小,但其降解产物丙烯酰胺会给生态环境和人类健康带来很大的危害。通过室内实验着重研究了ASP化学剂在土壤中的环境行为。通过室内土柱模拟实验,模拟了单元污染物(NaOH、LAS、PAM)和三元污染物在土壤中的自然迁移行为和模拟降雨情况下的迁移行为,考查了不同土壤类型(黑土、黄土、盐碱土)、不同时间、不同污染物数量对迁移情况的影响,得出污染物在土壤中的垂向迁移规律。此外也研究了PAM和LAS在环境(土壤、水体)中的吸附和降解行为,结果表明LAS在环境中降解速度较快;土壤对PAM有很强的吸附能力,一旦吸附很难再解吸下来。本论文从数值模拟理论角度出发,综合考虑了可溶性污染物在均质土壤/水环境体系中对流-弥散作用下的理想情况,以及可能存在的源汇情况,以土壤溶质迁移机理和质量守恒定律为基础,建立了描述饱和土壤/水环境中污染物迁移转化的数学模型,并以三个月内LAS在饱和土壤环境下的迁移模拟结果来验证对流-水动力弥散迁移模型的有效性。结果表明,对于饱和土壤环境污染物迁移过程的描述,模型有较强的适用性。本论文在对复杂的土壤环境进行了适度理想化假设的前提下,针对大庆油田典型的ASP化学剂泄漏情况进行了模拟计算,通过求解分析得到了特征污染物在土壤环境中的浓度分布及污染物理论迁移范围预测。ASP化学剂意外泄漏后一年内,对于特征污染物之一的LAS,其浓度值在经过短时间内的浓度积聚后,最终基本停留在土壤表层中呈规律性分布,其浓度最高值为14.5mg/L;另一特征污染物PAM同样呈规律性分布,但由于其特殊的物理化学性质,泄漏后10年后PAM主体浓度约为4.5mg/L,迁移边缘深至1.9m处,迁移进程比较缓慢;而特征污染物NaOH由于具有较好的水溶性和反应活性,迁移速度较快,三个月即有可能穿透土壤表层进入含水层,但是其浓度基本上可以忽略不计,对水质pH值的影响在国家安全标准范围之内。通过对这3组求解的独立分析,总结得出了可溶性污染物在土壤环境中存在的共性归趋规律。经过对三元复合驱中特征污染物在土壤中环境行为的全面分析,发现上述污染物进入土壤后基本都停留在土壤表层,即使在降雨、地表聚集着大量污染物的情况下,也不会影响到大庆地下水;特征污染物表面活性剂降解速度快,不是环境持久污染物,聚丙烯酰胺本身无毒性,其降解产物丙烯酰胺虽对环境和人类有很大危害,但降解速度很快,不被列为三元复合驱中主要污染物;特征污染物碱等同环境中一般碱类污染物,未磺化油等同环境中一般苯系污染物,为油田开发中常见污染物,呈现持久和难处理的特点,值得人们重视。更多还原

【Abstract】 Alkali-surfactant-polymer(ASP) compound flooding is a new method for tertiary oil recovery mentioned at the 80s of the 20th century. It is compounded by the alkaline, surfactant and polymer, containing the common advantage of surfactant and polymer flooding. It can improve oil displacement efficiency, increase the involved volume, meanwhile, it can reduce the usage of surfactant sharply. So it has been widely used in major oil fields, being a major measure to increase the oil productivity. However, as the ASP chemicals are applicated largely, the environment will be damaged inevitably. It is necessary to study and evaluate the pollutants environmental behaviors and impacts of ASP chemicals to provide a theoretical basis for environmental management of oil field and the reliable technology guarantee for the next ASP large-scale application.In this paper, according to the existing domestic and overseas environmental standards and evaluation methods, the main environmental particular pollutants in ASP are identified as alkali (sodium hydroxide), surfactant (linear alkylbenzene sulfonates, unsulphonic oil) and polyacrylamide (acrylamide) by modern analytical method. And the impact of main environmental particular pollutants in ASP on environment are analyzed in detail.The alkali and unsulphonic oil in ASP can cause enormous harms to ecological environment, showing the characteristics of durable and tractable. The toxicity of surfactant is related to the concentration and structure of surfactant. The polyacrylamide (PAM) is less environmental contamination and non-toxic to plants and animals, but its degradation product acrylamide (AM) can cause great harm to human beings and environment.The environmental behavior of ASP flooding chemicals in soil are studied with great focuses by experiments. The transfeering behavior under natural or simulated rainfall conditions of cell contaminant(sNaOH, LAS, PAM)and ternary pollutants are studied through the soil column experiments in different soils(black soil,loess soil,saline alkali soil), different times and different amount of pollutants. Effect of soil types (black soil,loess soil,saline alkali soil), time and amount of pollutants on the law of transferring in soil are investigated and the vertical migration law in soil are found. Moreover, the adsorption and degradation of PAM and LAS on the environment (river, soil) are also studied. LAS degradate fast in the environment. PAM has a high adsorptive affinity on soil and it is very difficult desorbed.This paper explained the conditions and building process of the migration and transformation model, established the mathematical equations and took series of possible extension in comprehensive consideration of soil solute transport mechanism, law of conservation of mass and the convection-dispersion of soluble contaminants in the homogeneous soil/water environment system under the ideal situation. Then, the equations, together with the initial conditions and the associated boundary conditions, make a specific meaningful soil solute transport model. In this paper, a one-dimensional soil column simulation of LAS migration in 3 months has been used as a validity comparison to the model application in the saturated soil environment. The results show that, for the description of contaminants migration process in saturated soil environment, model has a strong applicability. Contraposing the typical condition that ASP chemical agents have leaked of Daqing oilfield, simulation calculations have been carried out in the precondition of idealizing the complex soil environment. The distribution of contaminants concentration and the prediction of the range of theoretical migration have been figured out by means of calculations and analysis. After ASP chemical agents accidentally leaking within one year, the value of LAS concentration accumulate in a short period of time, then stay in the soil surface regularly. The highest concentration value is 14.5 mg/L. PAM, another sort of contaminants, due to its special physical and chemical properties, the concentration of PAM is about 4.5 mg/L after 10 years though it was regularly distributed. The edge of migration deep into 1.9 m, it follows that the migration process has been slow. As for NaOH, which can penetrate into the aquifer from the soil surface in only three months because of its great water solubility and high reactivity. But the concentration can be negligible, for the impact of water pH is also within the scope of national safety standards. After the independent thorough analysis of the accidental leaked contaminants, a general common migration law of the soluble contaminants in the soil environment can be drawn as a conclusion.Based on the comprehensive analysis of environmental behaviors of ASP pollutants in soil, we can conclude that most particular pollutants in ASP stay in the soil surface.Even much more pollutants on soil surface under rainfall conditions, it will not affect groundwater of daqing; LAS is not a durable pollutant, for it has a fast degradation speed. The polyacrylamide (PAM) is non-toxic, the degradation product acrylamide (AM) of PAM can cause great harm to human beings and environment, but it can degradate quickly in the environment, so they should not be contained in the main pollutants of ASP flooding. The alkali equivalent to the general alkaline pollutant, and the unsulphonic oil can be seemed as benzene pollutant. They are very common in the development of oil field, showing the characteristics of durable and intractable, so they should worth more attention of human beings.更多还原