超临界流体萃取致密介质中原油的可行性研究

发布时间：2018-01-13 00:00

  本文关键词：超临界流体萃取致密介质中原油的可行性研究　出处：《西南石油大学》2015年硕士论文　论文类型：学位论文

  更多相关文章： 致密油 孔隙介质 超临界CO_2萃取 萃取率 传质

【摘要】：致密油是指夹在或紧邻优质生油层系的致密碎屑岩或者碳酸盐岩储层中,没有经过长距离运移而形成的石油聚集,在中国陆相沉积盆地分布广泛,已在鄂尔多斯、松辽、准噶尔等盆地获得一些重要发现。它的自然能量一般很小,原油性质比较好,主要以轻质原油为主,地下流动状况比较好。致密油的赋存状态主要表现在三个方面：一是原油以薄膜状涂抹在颗粒的表面；二是原油以短柱状集合体发育于颗粒间微孔内,相互粘连；三是原油黏结于裂缝两壁。致密油藏,由于其储层岩性致密、渗流阻力大、压力传导能力差,导致油藏有效驱替系统难以建立。 超临界CO2具有强渗透性和对有机物的高溶解能力,它可渗透到致密基质中溶解原油,在不能建立有效驱替情况下,利用其对原油的抽提(萃取)作用开采原油。首先,超临界流体溶解原油分子依靠分子的扩散作用进入到储层的基质中,和基质里面的原油发生传质作用,使原油溶解于超临界流体中；溶解后的原油,通过超临界流体很强的渗透力,使其通过孔道扩散出来,在这个过程中,实现了超临界流体与原油两者之间的交换。超临界CO2兼有气液两相的双重特点,既具有与气体相当的高扩散系数和低粘度,又具有与液体相近的密度和对物质良好的溶解能力,表现出极好的溶解性、传递性和流动性。把在其他领域应用成熟的超临界流体萃取技术运用到致密介质中原油的萃取,为建立此类原油的开采技术的可行性提供指导。 论文分析了常规流体萃取固体物料的机理,在溶剂化缔合观点的基础之上,提出了超临界流体缔合萃取机理,建立了超临界缔合萃取固态物料的数学模型。通过对建立的萃取数学模型进行分析求解,得到了宏观萃取速率的数学方程；并对所建立的数学模型进行了实验验证。发现在30min-120min时间范围内,宏观萃取速率逐渐减小；在120min-180min的时间段内,宏观萃取速率基本保持不变。 在了解致密油储层物性的基础之上,通过实验对超临界CO2萃取饱和油岩心的规律进行了深入研究,并分析了各个参数对萃取率的影响规律。研究表明：萃取饱和油岩心时,萃取率随着压力的增加而增大,并且在临界点附近增大得最快；温度对萃取率的影响比较复杂,会出现萃取率减小的情况；萃取率会随着浸泡时间和循环时间的延长而增大,120min达到最好,最后基本都不再增加。实验条件下得到的最优参数方案为：压力20MPa、温度50℃、浸泡时间120min、循环时间150min,此时萃取率将会达到最大。和普通溶剂的洗油率相比,超临界C02萃取的效率具有很大优势。
[Abstract]:Dense oil is a kind of petroleum accumulation which is not formed by long distance migration and is widely distributed in continental sedimentary basins of China because of the tight clastic rock or carbonate reservoir which is sandwiched in or adjacent to the high quality oil source system. Some important discoveries have been made in Ordos, Songliao and Junggar basins. Its natural energy is generally very small, and its crude oil properties are relatively good, mainly light crude oil. The occurrence of dense oil is mainly shown in three aspects: first, the crude oil is smeared on the surface of particles in the form of thin film; Second, the crude oil develops in the micropore between the particles with short columnar aggregates and adheres to each other; The third is that the crude oil is bonded to the fractured two walls. Because of its tight lithology, large seepage resistance and poor pressure conductivity, it is difficult to establish an effective displacement system in a tight reservoir. Supercritical CO2 has strong permeability and high solubility to organic matter, it can permeate into dense matrix to dissolve crude oil, without establishing effective displacement. Firstly, the molecules of supercritical fluid dissolved crude oil enter into the reservoir matrix by molecular diffusion, and the crude oil in the matrix has mass transfer. Dissolving crude oil in supercritical fluids; The dissolved crude oil diffuses through the pores through the strong permeability of the supercritical fluid, and in the process. The exchange between supercritical fluid and crude oil has been realized. Supercritical CO2 has the dual characteristics of gas-liquid two-phase, which has high diffusion coefficient and low viscosity. It also has similar density to liquid and good solubility to substance, showing excellent solubility. The application of mature supercritical fluid extraction technology in other fields to the extraction of crude oil in dense medium provides guidance for the feasibility of establishing the extraction technology of this kind of crude oil. In this paper, the mechanism of conventional fluid extraction of solid materials is analyzed, and the supercritical fluid association extraction mechanism is proposed on the basis of solvation association theory. The mathematical model of supercritical association extraction of solid material was established, and the mathematical equation of macro extraction rate was obtained by analyzing and solving the mathematical model of extraction. The experimental results show that the macroscopic extraction rate decreases gradually in the range of 30min-120min. In the period of 120 min-180 min, the macro extraction rate remained basically unchanged. On the basis of understanding the physical properties of tight oil reservoir, the rule of supercritical CO2 extraction of saturated core is studied through experiments. The influence of various parameters on extraction rate is analyzed. The results show that the extraction rate increases with the increase of pressure and increases fastest near the critical point. The influence of temperature on the extraction rate is complex and the extraction rate will decrease. With the increase of immersion time and cycle time, the extraction rate will reach the best value for 120min, and no increase will be achieved in the end. The optimum parameters under the experimental conditions are as follows: pressure 20MPa. When the temperature is 50 鈩，

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