【作者】 张向宇；

【导师】 吴文祥；

【作者基本信息】 大庆石油学院 ， 油气田开发工程， 2010， 博士

【摘要】 聚合物/表面活性剂二元复合驱油体系中由于没有碱的存在,减少了碱对驱油效果和地面设备的不利影响,但同时也会使油水间的界面张力升高,很难达到超低界面张力(<10-3mN/m数量级),不利于提高驱油效率;没有了碱与表面活性剂的协同效应,会大大增加表面活性剂的吸附量,不利于经济成本。要想使无碱二元复合驱油体系具有与三元复合驱油体系同样低的界面张力,这就对表面活性剂提出了更高的要求。本文根据有关在无碱条件下形成超低界面张力机理的新理论设计合成了一种能够在无碱条件下使油水间的界面张力达到超低(<10-3mN/m数量级)的新型表面活性剂。通过室内实验,研究了这种表面活性剂的界面张力特性、界面张力稳定性、以及对不同油水条件的适应性和吸附特性等,并且对无碱二元复合驱油体系和三元复合驱油体系中活性剂的吸附量进行了对比分析。结果表明,这种活性剂完全能够满足无碱二元复合驱油体系对活性剂的要求。实验研究了无碱二元复合驱油体系的粘弹性和对水驱后残余油的启动和运移规律,在突扩、突缩等模型中通过理论计算研究了弹性对驱油效率的影响。结果表明,表面活性剂浓度对无碱二元体系的粘弹性影响不大,而聚合物浓度、分子量、二价离子浓度、矿化度、剪切速率等因素对粘弹性的影响较大,驱油体系的弹性越大,对驱油效率的贡献越高。通过室内人造岩心物理模拟实验,研究了不同分子量聚合物的流动特性。研究表明,在气测渗透率大于0.3μm2的岩心上可以使用分子量为2.5×107以下的所有聚合物(包括分子量为2.5×107的聚合物)。在均质和不同变异系数的二维纵向非均质人造岩心上开展了无碱二元驱油体系驱油效果以及活性剂浓度、二元体系段塞尺寸、聚合物浓度、变异系数、注入时机和渗透率等因素对无碱二元驱油体系驱油效果的影响规律,并与聚合物驱油体系、强碱三元复合驱油体系、弱碱三元复合驱油体系进行了驱油效果的对比分析。结果表明,随着活性剂浓度和二元段塞尺寸的增加,化学剂用量增加,无碱二元复合驱油体系的提高采收率幅度增加,但是增加到一定值后,增幅会变缓;聚合物等浓度条件下,当主段塞聚合物浓度由500mg/L增加到2500mg/L,无碱二元体系化学驱采收率呈明显提高的趋势;在变异系数相同的条件下,随着模型的渗透率的增加,无碱二元体系提高采收率幅度呈增加的趋势;在渗透率相同的情况下,变异系数增加,无碱二元体系的复合驱采收率都随着变异系数的增大而增大,而总采收率随变异系数的增大而降低;提前转注无碱二元复合驱油体系,能够提高采收率幅度;岩心渗透率和变异系数一定时,磺基甜菜碱表面活性剂无碱二元体系驱油效果要好于重烷基苯磺酸盐氢氧化钠强碱三元体系和石油磺酸盐碳酸钠弱碱三元体系。更多还原

【Abstract】 Due to the nonexistence of alkali in polymer-surfactant flooding system,the influence of alkali on displacement effect and equipments on the surface decreases, but at the same time, the interfacial tension between oil and water increases so that ultra-low interfacial tension (<10-3mN/m order) is hard to achieve, which is of disadvantage to improve displacement efficiency; without the synergistic effect between alkali and surfactant, the adsorption capacity of surfactant will greatly increase, which is of disadvantage to economies. In order to get the same low-interfacial tension of polymer-surfactant flooding system as ASP flooding system, the quality of surfactant will be highly required. Based on a new theory of the achievement of ultra-low interfacial tension with the nonexistence of alkali, a new type of surfactant which can help to get the ultra-low (<10-3mN/m order) interfacial tension was synthesized in this paper. Through the experiments in the lab, the interfacial tension properties,interfacial tension stability and the adaptability and the absorption characteristics under different oil-water conditions of this surfactant were studied,moreover, the amount of surfactant adsorption of the polymer-surfactant flooding system and ASP flooding system were compared and analyzed. The result shows that the requirement could be completely satisfied, using this type of surfactant.In the Experiment, the viscoelasticity of the two-component combinational flooding system without alkali and the start-up and migration laws of the residual oil after water flooding were studied,and through the sudden expansion,sudden contraction and other model the impact of elasticity on the oil displacement efficiency was studied. The results showed that the concentration of the alkali-surfactant had little effect on the viscoelasticity of the two-component system no alkali,while the polymer concentration,divalent ion concentration,salinity,shear rate and other factors had greater effect on the viscoelasticity. The greater the elasticity of the flooding system is, the higher the contribution on the oil displacement efficiency.Through the laboratory artificial core physical simulation experiments, the flow characteristics of different molecular weight polymer as well as the influence law of the two-component surfactant-polymer flooding slug size on the flooding effect of the alkali-free two-component flooding system were studied, which were used to select the formulas of the alkali-free two-component flooding system. Studies have shown that the core whose gas log permeability is greater than 0.3μm2 can use all the polymers whose molecular weight lower is than 2.5×107 (including the polymer whose molecular weight is 2.5×107);with surfactant concentration and slug size increases,the amount of chemical agents were increased,and the EOR range of alkali-free two-component flooding system was increased,but after it was increased to a certain value,the increase will be slowed.In the homogeneous and two-dimensional vertical heterogeneity of different variation coefficients artificial cores, the experiments about the alkali-free two-component system flooding effects as well as the influence law of coefficient of variation,injection timing,permeability and other factors on the flooding effect of alkali-free two-component flooding were conducted, and a comparative analysis was made on the flooding effect of the two-component flooding system with polymer flooding system, alkali ASP flooding system,and weak base ASP flooding system.The results showed that in the homogeneous cores with the same polymer concentration,when the main slug polymer concentration increased from 500mg/L to 2500mg/L,alkali-free two-component system chemical flooding recovery efficiency had the trend of obvious improvement;in the same coefficient of variation conditions,with the permeability of the model increases,the oil recovery efficiency improvement range of alkali-free two-component system showed an upward trend;in the case of the same permeability, the coefficient of variation increased,the alkali-free two-component system recovery efficiency increased, while the total recovery rate decreased as the coefficient of variation decreased;injecting alkali-free two-component flooding system ahead could improve the recovery efficiency; when core permeability and the coefficient of variation are constant,the flooding effect of alkali-free sulfobetaine surfactants-polymer flooding system was better than the displacement characteristics of ASP flooding solution and the weak base ASP flooding solution.更多还原