【作者】 叶安平；

【导师】 郭平；

【作者基本信息】 西南石油大学 ， 油气田开发工程， 2013， 博士

【摘要】 将CO2作为驱油剂来提高原油采收率的方法已成为油藏重要的开发方式之一。特别对于低渗致密油藏,由于这类储层多孔介质具有比面大、吸附量大、孔道小、毛管压力大、丰度低、油质轻等特点,导致低渗、低产、注不进采不出,常规开发方式效益差或不能有效开发,国内外研究和实践表明注CO2是开发低渗致密油藏的有效方式之一。而且随着近年来全球气候的持续变暖,温室气体的排放日益受到人们的关注。很多国家都签订了以减少温室气体为宗旨的《京都议定书》,我国作为CO2排放量第二的国家,不管是从国际社会的责任,还是从我国实现可持续发展和创建和谐社会的角度来出发,都迫切需要解决CO2减排的问题。而CO2减排的主要途径就是地质埋存,将CO2作为驱油剂注入低渗致密油藏储层中,不仅可以解决低渗致密油藏动用难问题,而且还可以同时实现CO2的长期埋存,具有十分广泛的应用前景。CO2气源丰富,容易混相,驱油效率高,在油藏条件下研究CO2与原油接触时的非平衡扩散对确定储层注入CO2与原油吞吐、脉冲和超前注气关井时间、注气速度与扩散速度的匹配、油气过渡带描述、混相条件等都有重要的理论与现实意义,所以对CO2与原油在多孔介质中的非平衡扩散研究十分必要。本文从非平衡扩散入手,分别从理论和实验两方面进行多孔介质非平衡扩散研究。本研究由国家自然科学基金项目(“多孔介质中CO2-多组分原油非平衡扩散理论研究(21143011)”)资助。本文在大量的国内外文献调研的基础上,从理论和实验两个方面来研究多孔介质中的气体与原油的非平衡扩散。在借鉴国内外分子扩散研究的基础上,首先建立了测试多组分气体-原油在PVT筒中的分子扩散实验测试方法,并在不同的实验条件下进行了四组实验测试；其次建立了多组分气体-原油在多孔介质中的分子扩散实验测试方法和扩散理论模型,以及相应的多孔介质扩散系数理论计算方法,并在不同的温度条件下进行了两组实验测试。通过研究,本文取得的主要成果如下：(1)建立了多孔介质中多组分气体—原油扩散实验测试方法,测试了气体扩散过程中体系压力随时间的变化关系、体系达到平衡的时间以及平衡后油气组成；(2)建立了多孔介质中多组分气体-原油扩散系数理论计算方法,在该模型中引入了分形毛管压力；(3)计算高温高压多孔介质中CO2-原油体系分子扩散系数；分析了体系温度以及原油组分对扩散系数的影响；(4)为了分析多孔介质对CO2-原油体系分子扩散系数的影响,分别进行了PVT筒中和全直径岩心中的扩散实验。研究结果表明,在相同的实验条件下,同一组分在多孔介质中的分子扩散系数比PVT筒中的小很多,这说明了多孔介质的存在对扩散系数有明显的影响。(5)分析了多孔介质中孔隙度和渗透率对模型的影响。本文的研究进一步完善了油气相态理论,为今后的研究提供了思路和方向。对于低渗致密油藏的注气开发具有重要的理论和现实意义。更多还原

【Abstract】 CO2as an oil displacement agent for enhanced oil recovery method has become one of the important way of reservoir development. Especially for the low permeability tight reservoir, due to the porous medium of the reservoir has the large specific surface area, large adsorption capacity, small pore, large capillary pressure, low abundance and lightweight oil, which result in low permeability and production, and injection cannot be carried out or oil cannot be produced. The regular development way benefits poor or cannot effectively develop. Research and practice show that CO2injection is one of the effective ways to develop the low permeability tight reservoir at home and abroad.In recent years, the global climate continues to warm. The greenhouse gas emissions are paid more and more attention by people. Many countries have signed the Kyoto Protocol for the purpose of reducing greenhouse gas. China ranks second for the CO2emission. No matter from the responsibility of the international community, or from the viewpoint of sustainable development and creating a harmonious society in our country to set out, we are in urgent need to solve the problem of CO2emission reduction.The main way of CO2reduction is geological storage. CO2as an oil displacement agent is injected into the low permeability tight reservoir, which can not only solve difficult problems, but also can achieve long-term sequestration of COt at the same time. This process has the very broad application prospect. CO2has rich gas source, and it is easily miscible whit oil. CO2injection has high oil displacement efficiency. When CO2is in contact with crude oil under the reservoir condition, the non-equilibrium diffusion has important theoretical and practical significance to determine the shut-in time, match the air injection rate and the diffusion rate, describe transition zone of oil and gas and the miscible condition. The research on the non-equilibrium diffusion of CO2and oil in porous media is necessary.Non-equilibrium diffusion in porous medium is investigated through the theoretical and experimental methods. Also, this study is granted by the National Natural Science Foundation of China(theory research on non-equilibrium diffusion of CO2-multicomponent crude oil in porous media).Based on numerous literature researches at home and aboard, Non-equilibrium diffusion in porous medium is investigated through the theoretical and experimental methods. On the basis of study of the international and domestic molecular diffusion, firstly, establish the experimental test method of molecular diffusion between multi-components gases and actual crude oil in the PVT cell, and conduct four groups of testing experiments under different experimental conditions. Secondly, create the experimental test method and diffusion theory model of molecular diffusion between multi-component gases and actual crude oil in porous media, and the corresponding theoretical calculation method. The two sets of experimental testing are carried out under different temperature conditions.The main results achieved in this article are as follows:(1) Establish the experimental test method of molecular diffusion between multi-component gases and actual crude oil in porous media, and test the relationship between pressure and time in the diffusion process, oil-gas composition at final equilibrium state as well as the equilibrium time.(2) Establish the diffusion theory model and corresponding theoretical calculation method of molecular diffusion between multi-component gases and actual crude oil in porous media, consider1the fractal capillary pressure in this mode.(3) Calculate the molecular diffusion coefficient of CO2-oil system under high temperature and pressure in porous media, and analyze the influence of the system temperature and component of the crude oil on the molecular diffusion coefficient.(4) Compare the diffusion coefficient test of CO2-oil in PVT cell and in porous medium. And discuss the influence of porous medium on diffusion visually. Study indicated that porous medium hindered the molecular diffusion at some degree. And at the same temperature and pressure condition, diffusion coefficient of components of the same system at porous medium is smaller than that in PVT cell.(5) Analyze the influence of porosity and permeability on the molecular diffusion coefficient in porous media.更多还原