考虑BET吸附的页岩气渗流模型及压力分布研究

发布时间：2018-05-09 06:42

本文选题：页岩气 + BET吸附　；参考：《东北石油大学》2017年硕士论文

【摘要】：通过对大量页岩气藏相关文献的查阅与汇总,根据对近年页岩气藏的研究开发情况的了解,确立了研究课题。目前,页岩气藏的相关研究将吸附/解吸附、滑脱、扩散——三大流动特性纳入到考虑范畴内,可是对于吸附类型、扩散类型的确定主要靠前人经验,选择兰格缪尔(Langmuir)吸附模型和克努森(Knudsen)型扩散模型进行描述。本文的创新之处在于建立BET吸附控制下的渗流模型以及分析不同扩散类型、吸附类型对压力分布所产生的影响。对于页岩气的有效开发利用,研究页岩气藏的渗流理论以及数学模型具有非常重要的意义。在理解页岩气藏的基本特征以及吸附/解吸附、滑脱、扩散三种流动特征的基础上,建立了页岩气藏的数学模型,并进一步得出数值模型。建立模型是深刻认识并分析页岩气在气藏中运移产出机理的重要途径。而后简化这种过程及模型,研究页岩气藏压力分布的求解,确定了压力与距离的对应函数关系。利用控制变量法,通过参数调节,求出了考虑不同吸附类型、扩散类型的压力分布,并绘制压降曲线以比较不同扩散类型、吸附类型对压力分布的影响。主要完成了以下几方面的研究工作:(1)通过对过去5年相关文献的查阅,了解了页岩气藏的勘探开发研究近况,并对开发过程中所遇到的问题及最新的理论技术进行汇总,掌握页岩气藏研究动态。(2)总结并比较了热成因与生物成因的原理与影响因素,并对混合成因进行介绍,得出热成因占主要方面,并且页岩气组分及总量受环境因素影响而复杂多变的结论;通过查阅大量文献对页岩气藏的孔渗特征、赋存方式、特殊评价指标进行系统地总结分析,为后续研究奠定理论基础。(3)系统研究了页岩气的特殊运移机理,基于三种吸附模型的比较,选用了BET吸附模型,认识到克努森数对扩散类型的判断起决定作用,滑脱效应的存在引起了表观渗透率的增大,为模型的建立提供理论依托。(4)基于对页岩气特殊运移机理的研究,作出假设,区分基岩、裂缝系统,气、水两相,建立考虑BET吸附的数学模型,再进行差分得到数值模型。(5)简化渗流模型,建立流动控制方程,求解压力分布与半径的对应关系。利用控制变量的思想,改变解吸附量和克努森数,即可达到比较各种吸附类型、扩散类型控制下压力分布异同的目的,通过二分法计算机编程解方程并绘制出压降曲线,更直观地比较出,对于符合BET吸附的气藏,选用兰格缪尔吸附描述会使压力低于真实压力水平,三种扩散类型下的压降速度,由快到慢为克努森扩散、过渡扩散、F菲克扩散。对于压力分布,扩散比吸附的影响要小。
[Abstract]:Through consulting and summarizing a large number of relevant documents of shale gas reservoir, according to the understanding of the research and development of shale gas reservoir in recent years, the research subject is established. At present, the related research on shale gas reservoirs takes the three flow characteristics of adsorption / desorption, desorption and diffusion into consideration. However, for adsorption types, the determination of diffusion types is mainly based on the previous experience. Langmuir adsorption model and Knudsen Knudsen-type diffusion model were selected to describe the results. The innovation of this paper lies in the establishment of seepage model controlled by BET adsorption and the analysis of the influence of different diffusion types and adsorption types on the pressure distribution. For the effective development and utilization of shale gas, it is of great significance to study the percolation theory and mathematical model of shale gas reservoir. On the basis of understanding the basic characteristics of shale gas reservoir and three characteristics of adsorption / desorption, detachment and diffusion, the mathematical model of shale gas reservoir is established, and the numerical model is obtained. Modeling is an important way to understand and analyze the migration and production mechanism of shale gas in gas reservoirs. Then it simplifies the process and model, studies the solution of shale gas reservoir pressure distribution, and determines the corresponding function relationship between pressure and distance. By using the method of controlling variables and adjusting the parameters, the pressure distribution considering different adsorption types and diffusion types is obtained, and the pressure drop curve is drawn to compare the influence of different diffusion types and adsorption types on the pressure distribution. Mainly completed the following aspects of research work: 1) through the review of relevant documents in the past five years, we have learned about the recent research situation of shale gas reservoir exploration and development, and summarized the problems encountered in the process of development and the latest theoretical techniques. This paper summarizes and compares the principles and influencing factors of thermal and biological origin, and introduces the mixed origin, and concludes that thermal genesis is the main factor. And the conclusion that the composition and total amount of shale gas is influenced by environmental factors is complex and changeable. Through consulting a large number of literatures, the characteristics of pore and permeability, occurrence mode, special evaluation index of shale gas reservoir are systematically summarized and analyzed. The special migration mechanism of shale gas is studied systematically. Based on the comparison of three adsorption models, BET adsorption model is selected, and it is recognized that Knudsen number plays a decisive role in the determination of diffusion type. The existence of slip effect leads to the increase of apparent permeability, which provides theoretical support for the establishment of the model. Based on the study of the special migration mechanism of shale gas, it makes a hypothesis to distinguish the bedrock, fracture system, gas and water two phases. A mathematical model considering BET adsorption was established, and then the numerical model was obtained by differential method. The seepage model was simplified, the flow control equation was established, and the corresponding relation between pressure distribution and radius was solved. By using the idea of controlling variables and changing the amount of desorption and Knudsen number, the purpose of comparing the pressure distribution under the control of various adsorption types and diffusion types can be achieved. The equation is solved by a binary computer and the pressure drop curve is drawn. It is more intuitively compared that for gas reservoirs in accordance with BET adsorption, the pressure will be lower than the true pressure level by using Langmuir adsorption description, and the pressure drop rate under three diffusion types will change from fast to slow to Knudsen diffusion, and transition diffusion will result in F-Fick diffusion. For pressure distribution, the effect of diffusion is less than that of adsorption.
【学位授予单位】：东北石油大学
【学位级别】：硕士
【学位授予年份】：2017
【分类号】：TE312

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