【作者】 兰玉波；

【导师】 宋考平；

【作者基本信息】 大庆石油学院 ， 油气田开发工程， 2006， 博士

【摘要】 自二十世纪五十年代开始，国内外就着手进行了油田开发晚期或水驱结束后的化学驱油技术研究，而在九十年代化学驱油作为我国注水开发油田提高采收率的重要方法，已经从机理研究、配方优选进入到先导性矿场试验阶段，特别是聚合物驱油技术已在大庆油田实现了工业性应用，并取得了明显的增油降水效果。但是由于化学驱机理十分复杂，人们对其中的许多基础性问题仍缺乏足够的认识。因此，为了进一步提高化学驱的驱油效果，完善化学驱油机理，有必要对化学驱中的物理化学渗流机理进行深层次的、系统的研究。这也正是“十五”期间国家重点基础项目“大幅度提高原油采收率的基础研究”的目的，“化学驱驱油效率和波及系数研究”即属该项目的部分内容。本文在对国内外有关水驱与化学驱的波及系数和驱油效率资料调研基础上，以大庆油田为依托，充分利用丰富的密闭取心检查井岩心分析资料，总结出了大庆油田的水驱波及系数和驱油效率的变化特征，定量给出了大庆油田目前的水驱波及系数和驱油效率；依据砂岩油田的沉积规律，按照物理模拟的相似理论，设计出与大庆油田主力油藏相似的二维及三维非均质物理模型，并通过微观网络模型、大型二维平面均质模型及三维物理模型的驱油实验，对化学驱渗流机理、波及系数及驱油效率进行了研究，揭示了聚合物驱和三元复合驱的驱油效率、波及系数和最终采收率值大小，以及驱油效率和波及系数对采收率提高值的贡献。特别是，对聚合物能否提高驱油效率给予了肯定的回答。主要研究结论可归纳为下述几点：1、设计并制作了五种大型物理模拟实验用的物理模型，从阿尔奇原理出发，通过测量电极间的电阻率来判断油层的含油饱和度，建立了一套由电极、数据采集板和数据输出终端(电脑)构成的自动化程度较高的测量、采集系统。饱和度测量误差在1.0～1.5个百分点之间。实现测定化学驱不同驱替阶段岩心内的含油饱和度分布和化学驱的前缘位置。2、建立了微观驱油动态彩色图像量化处理系统。主要具有以下几方面的功能：①实现对微观驱油实验过程动态图像的连续录取(时间间隔约为1.5秒)；②对驱替过程的动态图象进行分析得到不同驱替倍数下的采出程度并绘制采收率曲线；③显示宏观目标(如水前缘)在整个模型中的运动轨迹；④在适当的放大倍数下，跟踪录取目标(如油珠)在孔隙中的运动情况，计算目标在每一时刻的特征参数，得到目标的运动轨迹；⑤对模型内的孔隙参数进行分析，得到微观模型孔隙、喉道的特征值。3、通过密闭取心检查井岩心资料和储层预测分析与研究，宏观上给出了大庆油田不同类型储层的水驱波及系数和驱油效率。水驱波及系数变化范围在41.4％～67.7％之间，水驱驱油效率处于40.0％～65.0％之间，平均为为53.2％左右。4、微观和岩心驱油实验结果均表明，聚合物驱的主要作用在于提高波及系数，而且主要是提高中低渗透层的波及系数其驱油机理是：(1)流度比的降低提高了聚合物驱的波及系数；(2)聚合物溶液剪切应力的增加，可以驱替孤岛状、膜状剩余油。(3)聚合物溶液的粘弹性可以减少盲状剩余油。5、室内岩心模拟实验表明聚合物驱可提高驱油效率8％左右。非均质有隔层低渗透储层波及系数提高21.9％左右，中渗透提高波及系数10.1％左右，高渗透层提高波及系数7.1％；而非均质无隔层低渗透储层波及系数提高42.2％左右；中渗透提高波及系数23.4％左右，相比于有隔层模型来说，无隔层模型的水驱波及系数相对低一些，但是波及系数提高值却是相反。6、三元复合驱既能提高驱油效率，又能提高波及系数，其驱油机理是：(1)超低界面张力的作用，增加了毛管数，降低了剩余油含油饱和度，提高驱油效率；(2)聚合物的加入，增加了驱替剂的粘性，降低了油水流度比，减缓了指进现象，改善了驱替液的流场分布，增加了驱替液的波及系数；(3)三元复合体系与原油形成乳状液，在运动过程中不断碰撞、聚并，并逐渐形成油墙，扩大波及范围并将更多的微观残余油乳化分散成油滴驱替出来。(4)表面活性剂与碱的加入，改变了油层的润湿性。7、三元复合驱提高驱油效率值为32.18％。三元复合驱结束后，低渗透层波及系数增加了30.5％；中渗透层波及系数增加27.4％，高渗透层波及系数比水驱结束时增加14.8％。而无隔层模型相对于有隔层模型来说，中渗透层提高波及系数幅度相对较高。8、从驱油效率和波及系数对采收率的贡献程度上看，聚合物驱驱油效率对提高采收率的贡献为11.85％，三元复合驱贡献为33.27％。三元复合体系充分发挥了其协同效应，大幅度提高了原油采收率，但为了充分发挥三元复合体系的驱替效果，应主要将三元复合体系注入到高渗透油层，同时将中低渗透油层用聚合物驱，之后进行二元体系驱替中低渗透层，实现总量不变的情况下，大幅度提高原油采收率。更多还原

【Abstract】 Since 1950s the chemical flooding after the water flooding or at the later period of oilfield-exploited has been studied in our country and abroad. In 1990s, as the main technology to improve the oil recovery in water-injected exploited oilfield, chemical flooding has been into the period of pilot test, the technology of polymer flooding has been applied in industrial scale and obtained good effect. However, the mechanism of chemical flooding is very complicated and many basic problems of it are still lack of enough understanding. So, in order to improve the mechanism and effect of chemical flooding, it is necessary to do deeper and systematical work about the physi-chemical seepage mechanism. This is the purpose of "the foundational research about improving the oil recovery greatly" (a national key project in "10th-five-years" period), "the study on oil displacement efficiency and sweep coefficient of chemical flooding" is part of the project.On the basis of the information analysis about the sweep coefficient and oil displacement efficiency of water flooding and chemical flooding, utilizing the plenty of the sealed coring inspection well data of Daqing oilfield, the dynamic characters of sweep coefficient and oil displacement efficiency of water flooding in Daqing oilfield were concluded, the sweep coefficient and oil displacement efficiency of water flooding in Daqing oilfield at present were given quantitatively. According to similarity theory and the sediment rule, the two-dimensional and three-dimensional heterogeneous physical models similar to the reservoir of Daqing oilfield were designed and produced. The seepage mechanism of chemical flooding, sweep coefficient, oil displacement efficiency were investigated by the core flooding tests with micro-model, two-dimensional planar homogeneous physical model and three-dimensional heterogeneous physical model. With these experiments the oil displacement efficiency, sweep coefficient and the last oil recovery of polymer flooding and ASP flooding were obtained, the contribution of oil displacement efficiency and sweep coefficient to enhanced oil recovery was also studied. The study confirms that polymer flooding can improve the oil displacement efficiency. The main conclusions are as follow:1. 5 kinds of physical model for experiment were designed and produced. According to the Archie’s formula, the oil saturation in the model is obtained by the method to measure the electrical resistivity between the electrodes. A set of measurement, data acquisition system was established with the electrodes, data acquisition board and computer. The measurement difference of oil saturation is in the range of 1.0-1.5%. The distribution of oil saturation in the core at different period of chemical flooding and the position of chemical flooding front can be measured.2. Dynamic color image quantitative analysis system of micro-model was established successfully. This system has several functions: (1) It can take the photo of the dynamic process of oil displacement in micro-model continuously (1 photo/1.5s); (2) The dynamic image in the flooding process can be analyzed to obtain the degree of oil displacement and draw the curve of oil recovery; (3) The movement of the macroscopical target (such as the water front) can be displayed; (4) At the proper magnifying factor the movement of the target (such as the oil drop) in pore can be tracked and photoed, the characteristic parameter of the target can also be calculated, then the movement track of the target would be obtained; (5) The pore parameters of the micro-model can be analyzed to obtain the characters of the pore and throat.3. With the analysis of sealed coring well data and reservoir prediction, the sweep coefficient and oil displacement efficiency of water flooding in the various reservoirs of Daqing oilfield are given macroscopically. Now the sweep coefficient of water flooding in Daqing oilfield is in the range of 41.4%-67.7%, the oil displacement efficiency is in the range of 40.0%-65.0% and the mean value is about 53.2%.4. Both the micro-model experiment and core flooding test show that the main effect of polymer flooding is to increase the sweep coefficient, especially the sweep coefficient of middle and low-permeability layers. The mechanisms of polymer flooding are: (1) The decrease of mobility ratio improves the sweep coefficient of polymer flooding; (2) The shear stress of the polymer solution increases so it can displace the island and film remaining oil; (3) The visco-elasity of the polymer solution can reduce the amount of the "dead-ends" remaining oil.5. The core flooding test shows the polymer flooding can improve the oil displacement efficiency by about 8%. In a heterogeneous model with interlayer, the sweep coefficient can be increased about 21.9%, 10.1% and 7.1% at the low, middle and high-permeability layer respectively; while in a heterogeneous model without interlayer the sweep coefficient can be increased about 42.2% and 23.4% at the low and middle-permeability layer respectively. The sweep coefficient of the model without interlayer is a little lower than that of the model with interlayer, however, the increase of the sweep coefficient is inverse.6. The ASP flooding can not only increases the oil displacement efficiency, but also improves the sweep coefficient. The mechanisms of the ASP flooding are: (1) The ultra-low interfacial tension between oil and water can increase the capillary number and decrease the oil saturation of remaining oil, so it would improve the oil displacement efficiency; (2) The addition of the polymer can increase the viscosity of the system and decrease the mobility ratio, so it can improve the flow field, reduce the finger advace and increase the sweep coefficient; (3) The ASP system and crude oil can form the emulsion, the oil drop will aggregate continually and form the oil wall, then more and more residual oil will be emulsified and displaced; (4) The addition of surfactant and alkali changes the wettability of reservoir.7. The ASP flooding can increase the oil displacement efficiency by 32.18%. After the ASP flooding, in a heterogeneous model with interlayer, the sweep coefficient can be increased about 30.5%, 27.4% and 14.8% at the low, middle and high-permeability layer respectively. In contrast to the model with interlayer, the increase of sweep coefficient of middle-permeability layer in the model without interlayer is a little higher.8. As to the contribution of oil displacement efficiency to enhanced oil recovery, that of the polymer flooding is 11.85%, ASP flooding is 33.27%. The ASP system has significant synergic effect and it can enhance the oil recovery greatly. In order to make the best of the ASP system, firstly, the ASP system should be injected into the high-permeability layer and the polymer solution into the low and middle-permeability layer, then, the low and middle-permeability layer can be flooded with AS system. With this injection mode the oil recovery can be improved greatly at the same amount of chemicals.更多还原