基于格子Boltzmann方法的页岩气微观流动机理研究

发布时间：2018-02-11 10:57

本文关键词： 页岩气格子Boltzmann方法表面扩散气体滑移多尺度　出处：《西南石油大学》2015年博士论文　论文类型：学位论文

【摘要】：页岩气在世界范围内储量巨大,初步探明全球页岩气储量接近致密砂岩气和煤层气已探明的总储量,而中国页岩气储量丰富,开发潜力巨大。页岩中的纳米级孔隙决定了页岩气在储层中的赋存状态和流动特征,进而决定了页岩气藏的开发特征。目前,在页岩气藏的开发过程中产生了很多科学和技术问题。这一系列的问题导致传统的宏观渗流理论在描述页岩气流动时存在一定的局限性,从而难以准确描述页岩气的流动规律。运用微观或介观方法在不同尺度上模拟页岩气在页岩中的流动,进而从不同角度全面认识页岩气的流动机理,已成为该领域未来的发展方向。目前,针对页岩气流动机理的研究方法主要表现为如下三种：一是基于连续介质假设的宏观方法；二是微观分子动力学方法；三是介观模拟方法,如：直接模拟Monte-Carlo方法(DSMC),格子Boltzmann方法(LBM)。与其他方法相比,格子Boltzmann方法没有连续介质假设条件且具有较高的计算效率和较低的统计噪声,因此格子Boltzmann方法在模拟多尺度、多物理场的复杂流动问题上具有较大的优势。为此,本文将运用格子Boltzmann方法研究页岩气微观流动机理,分别从孔隙尺度和表征体元(REV)尺度研究了页岩气在页岩中的流动规律,具体研究内容和主要成果如下：(1)对国内外文献进行了大量调研,介绍了格子Boltzmann方法的介观特点,总结了页岩气流动机理的研究方法及研究现状。(2)从Boltzmann方程出发对格子Boltzmann方法原理进行了系统的论述,介绍了常用的边界格式和格子Boltzmann方法的程序结构。(3)研究了长方形格子Boltzmann模型,通过Chapman-Enskog多尺度展开,发现长方形格子Boltzmann模型恢复的宏观方程含有误差项,并建立了微尺度流动的长方形格子Boltzmann模型,对长方形格子Boltzmann模型的微尺度边界条件进行了详细的分析,提出了通过调节组合系数r(或离散调节系数σ)和松弛参数s4来消除数值离散效应的方法,并在计算效率和计算精度方面对长方形格子Boltzmamn模型和正方形格子Boltzmann模型进行了对比。(4)建立了理想气体条件和非理想气体条件下的格子Boltzmann模型。针对页岩气藏高压的特点,运用非理想气体的格子Boltzmann模型研究了气藏条件下页岩气在干酪根孔中的流动机理,进而总结出了页岩气在干酪根孔中流动的一些物理规律。(5)针对非理想气体,分析了用于处理曲线边界的反弹与完全漫反射边界条件,提出了该边界条件中组合系数的确定方法,并运用孔隙尺度格子Boltzmann模型模拟了人工构造多孔介质中页岩气的流动,分析页岩气在干酪根多孔介质中特殊流动规律对表观渗透率的影响。(6)建立了非理想气体条件下页岩气的REV尺度格子Boltzmann模型,在REV尺度上研究了含有天然裂缝的页岩中页岩气的流动规律,分析了天然裂缝对页岩气流动的影响。(7)由于纳米级干酪根孔中表面扩散的存在,尤其是页岩中天然裂缝的存在,使得页岩的整体渗透能力大幅度的增加,这也使得页岩气藏的经济开发变成了现实。
[Abstract]:The huge reserves of shale gas in the world, the total reserves of the world's shale gas reserves close to a preliminary study of tight sandstone gas and coal seam gas reserves, and shale gas reserves China abundant, with great potential of development. Nano pore shale determines the occurrence of shale gas in the reservoir and flow characteristics, and determine the the development characteristics of shale gas reservoirs. At present, produce a lot of scientific and technical problems in the development process of shale gas reservoirs. This leads to a series of problems of traditional macro percolation theory has some limitations in the description of shale gas flow, from the flow law and is difficult to accurately describe the shale gas. Using microscopic or mesoscopic method in different scale simulation of shale gas in shale flow, flow mechanism from different angles and comprehensive understanding of shale gas, has become the future development direction of this field. At present, the shale gas flow Study on the mechanism of the method mainly have the following three kinds: one is the macro method based on the continuum assumption; two is the micro molecular dynamics method; three is the mesoscopic simulation method, such as: direct simulation Monte-Carlo method (DSMC), the lattice Boltzmann method (LBM). Compared with other methods, the computational efficiency of lattice Boltzmann method without hypothesis the condition of continuous medium and high and low noise, so the lattice Boltzmann method in multi-scale simulation, has great advantages of complicated flow problems of multi physics field. Therefore, this paper will use the lattice Boltzmann method of shale gas micro flow mechanism, respectively from the pore scale and characterization of element (REV) flow the law on the scale of shale gas in shale, and the main results of the specific research contents are as follows: (1) a lot of research literatures at home and abroad, introduces the lattice Boltzmann method The mesoscopic characteristics, summarizes the current situation of research methods of shale gas flow mechanism and research. (2) from the Boltzmann equation the principle of lattice Boltzmann method is analyzed systematically, introduces program structure boundary scheme commonly used and lattice Boltzmann method. (3) studied the square lattice Boltzmann model, through Chapman-Enskog multi scale expansion found, macroscopic equations rectangular lattice Boltzmann model with recovery error term, and the establishment of micro scale flow rectangular lattice Boltzmann model, the micro scale of rectangular lattice Boltzmann model boundary conditions are analyzed in detail, put forward by adjusting the combination coefficient R (or discrete adjustment coefficient sigma) method to eliminate the numerical dispersion effect and S4 relaxation parameters, and the computing efficiency and accuracy of the rectangular lattice Boltzmamn model and Boltzmann model of square lattice Contrast. (4) established a lattice Boltzmann model of ideal gas and non ideal gas conditions. According to the characteristics of shale gas reservoir pressure, the lattice Boltzmann model with non ideal gas on the gas flow mechanism of shale gas reservoir under the condition of kerogen in the hole, and then summarizes some of the physical laws of shale gas flow the kerogen in the hole. (5) for non ideal gas for rebound and completely diffuse boundary condition curve boundary analysis method was proposed to determine the boundary conditions of combination coefficient, and the simulation of artificial structures shale gas flow in porous medium using pore scale lattice Boltzmann model, analysis of the impact of shale the gas in the kerogen in porous medium on the special flow law permeability. (6) established a REV scale lattice Boltzmann model for shale gas under non ideal gas conditions, on the scale of REV Flow law of shale gas containing natural fractures in shale, and analyzed the influence of flow of natural fracture of shale gas. (7) due to the surface diffusion of nano kerogen in the hole, especially natural fractures in shale, the shale overall permeability increases, which makes the economic development of shale the gas reservoir has become a reality.

【学位授予单位】：西南石油大学
【学位级别】：博士
【学位授予年份】：2015
【分类号】：TE31

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