多孔介质内油气混相与扩散特性实验研究

发布时间：2018-06-18 06:31

本文选题：多孔介质 + CO_2驱油　；参考：《大连理工大学》2015年硕士论文

【摘要】：大气中CO2浓度升高引发的温室效应对全球生态环境系统造成了极大的影响。CO2驱油(CO2-EOR)是目前有效的CO2减排方案之一。为了确保CO2驱油的经济性以及封存的安全性,测量油气的最小混相压力(MMP)是十分必要的。CO2在注入过程中以分子扩散形式进入原油中,扩散系数对驱油工程安全性评估以及整体性能预测等方面都是必要的数据。本文应用了X射线CT可视化技术,研究了油气两相相态随压力的变化特性以及恒温恒压条件下CO2在油相中的扩散过程。提出了基于X射线CT可视化技术观察油气相态变化及测量最小混相压力的方法,获得了油气系统的最小混相压力值,并与文献中传统实验方法测量值进行比较,验证了CT可视化方法的可靠性。实现油气相态变化过程中油相体积及接触角的实时测量。结果表明,油相体积随压力的增高成指数形式增大,两相接触角也随压力增高而增大。建立了基于CT可视化技术研究多孔介质中油气相态变化及混相的实验系统,开展了多孔介质中油气混相过程实验研究。分析了孔喉半径对混相的影响。结果表明,随着孔喉尺寸的减小,孔隙中流体受到的毛细管力增大,导致流体在多孔介质中的界面张力增大,最终增大了多孔介质内油气混相压力。提出了一种恒温恒压条件下测量CO2在油中扩散系数的实验方法。基于CT可视化技术和非迭代有限体积法,计算了CO2向油溶液中扩散过程的局部扩散系数。结果表明,CO2扩散系数沿着扩散方向逐渐降低,扩散系数随时间减小,并且实验中的整体扩散系数呈现随时间减小、随压力增大趋势。通过测量CO2在油饱和多孔介质中的扩散系数,分析了多孔介质对CO2扩散进程的影响。结果表明,多孔介质阻碍了CO2向油中的扩散,相比于CO2直接向纯油溶液扩散,CO2在多孔介质中的有效扩散系数明显偏小。
[Abstract]:Greenhouse Effect caused by the increase of CO _ 2 concentration in the atmosphere has a great impact on the global ecological system. Co _ 2-EOR is one of the effective CO2 emission reduction schemes. In order to ensure the economy of CO2 flooding and the safety of oil storage, it is necessary to measure the minimum miscible pressure (MMP) of oil and gas. Diffusion coefficient is necessary for safety evaluation and overall performance prediction of oil displacement engineering. In this paper, X-ray CT visualization technique is used to study the variation characteristics of oil and gas two-phase state with pressure and the diffusion process of CO _ 2 in oil phase under constant temperature and constant pressure. Based on the X-ray CT visualization technique, a method for observing the change of oil and gas phase behavior and measuring the minimum miscible pressure is proposed. The minimum miscible pressure of oil and gas system is obtained and compared with the traditional experimental method in literature. The reliability of CT visualization method is verified. The oil phase volume and contact angle can be measured in real time. The results show that the volume of oil phase increases exponentially with the increase of pressure, and the contact angle of two phases increases with the increase of pressure. An experimental system based on CT visualization was established to study the phase change and miscibility of oil and gas in porous media and the experimental study on the process of oil and gas miscibility in porous media was carried out. The influence of pore throat radius on the misphase is analyzed. The results show that the capillary force on the pore fluid increases with the decrease of the pore throat size, which leads to the increase of the interfacial tension of the fluid in the porous medium, and finally increases the oil / gas miscible pressure in the porous medium. An experimental method for measuring the diffusion coefficient of CO _ 2 in oil under constant temperature and constant pressure is presented. Based on CT visualization technique and non-iterative finite volume method, the local diffusion coefficient of CO _ 2 diffusion to oil solution is calculated. The results show that the diffusion coefficient of CO _ 2 decreases gradually along the direction of diffusion, and the diffusion coefficient decreases with time, and the overall diffusion coefficient decreases with time and increases with pressure. By measuring the diffusion coefficient of CO _ 2 in oil-saturated porous media, the influence of porous medium on the diffusion process of CO _ 2 was analyzed. The results show that the effective diffusion coefficient of CO _ 2 in porous medium is smaller than that in pure oil solution.
【学位授予单位】：大连理工大学
【学位级别】：硕士
【学位授予年份】：2015
【分类号】：TE357.7

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