基于格子Boltzmann方法的页岩气藏微观渗流机理研究

发布时间：2018-04-27 22:24

本文选题：页岩气藏 + 微尺度效应　；参考：《西南石油大学》2017年硕士论文

【摘要】：页岩气全球储量大,资源前景可观,是接替常规油气资源的重要选择。但页岩气藏特低孔,特低渗,微纳米级孔隙大量发育的储层物性特征,使得气体产出过程的运移机制异常复杂。基于连续介质假设条件的宏观渗流力学理论已经不能精确地表征页岩气渗流规律。针对于页岩气运移过程中微尺度效应,本文引入介观尺度方法一格子Boltzmann方法(LBM),分析了孔隙尺度及表征单元尺度(REV)页岩气渗流特征。本文研究内容为深化页岩气藏复杂渗流理论,为页岩气藏的高效开发提供一定的理论支撑。本文研究内容及相关成果如下:(1)通过大量国内外文献调研,分析了页岩气藏储层物性特征和气体运移机制,明确了页岩气产出伴有微尺度效应。(2)论述了格子Boltzmann方法的基本原理,推导了该方法的外力项方程,并给出了边界条件,分析了格子Boltzmann方法在页岩气藏微纳米级孔隙中气体渗流规律研究的适用性及优势。(3)将Langmuir等温吸附方程,Fick扩散定律与弹性-镜面组合边界格式(BSR)相耦合,建立了考虑页岩气微观渗流机制的格子Boltzmann模型;该模型考虑了页岩气的吸附—解吸,气体扩散,滑脱效应等机理,并对页岩气在孔隙中的流动进行了动态模拟,针对相关参数进行了敏感性分析。(4)将岩心电镜扫描图二值化得到了页岩基质孔隙空间中质点间的相关函数,再以质点间协方差的相关因子作为目标函数,优化了四参数随机生长法的参数,提出了适用于页岩气藏复杂物性的数字岩心方法;再运用格子Boltzmann方法求取岩心的孔隙度,孔隙迂曲度及固有渗透率等物性参数,与前人经验公式进行了对比分析,验证了数值算法的正确性。(5)在REV尺度,推导了页岩气渗流格子Boltzmann模型,分别模拟了气体在富含有机质的孔隙介质以及无机质孔隙中的渗流,建立了考虑岩石基质和天然裂缝的表征单元,模拟得到了天然裂缝的存在大幅度提高了页岩储层的全局渗透率的结论,印证了页岩气藏的高效开采应该尽可能沟通天然裂缝的理论。成果为页岩气渗流格子Boltzmann模型由孔隙尺度向矿场尺度进行升级提供了理论支撑。
[Abstract]:Shale gas is an important choice to replace conventional oil and gas resources because of its large global reserves and considerable resource prospects. However, the reservoir physical properties of very low porosity, ultra-low permeability and micro- and nanoscale porosity in shale gas reservoir make the migration mechanism of gas production process extremely complicated. The macroscopic percolation mechanics theory based on continuous medium hypothesis can not accurately characterize shale gas percolation law. Aiming at the microscale effect in shale gas migration, the mesoscopic scale method, lattice Boltzmann method, is introduced to analyze the pore size and the percolation characteristics of shale gas characterized by unit scale. The content of this paper is to deepen the complex percolation theory of shale gas reservoir and to provide certain theoretical support for the high efficiency development of shale gas reservoir. The research contents and related results are as follows: (1) based on a large number of domestic and foreign literature, the physical characteristics and gas migration mechanism of shale gas reservoirs are analyzed, and the basic principle of lattice Boltzmann method is discussed. The external force term equation of the method is derived, and the boundary conditions are given. The applicability and advantage of lattice Boltzmann method in the study of gas percolation law in shale gas reservoir in micro-nanometer pore are analyzed. The Langmuir isothermal adsorption equation is coupled with the elastic-mirror combined boundary format (BSRs). A lattice Boltzmann model considering the microscopic percolation mechanism of shale gas is established, which takes into account the adsorption and desorption mechanism, gas diffusion and slippage effect of shale gas, and simulates the flow of shale gas in pores dynamically. Sensitivity analysis of correlation parameters. 4) the correlation function between particles in shale matrix pore space is obtained by binarization of scanning electron microscope (SEM) diagram of core, and the correlation factor of covariance between particles is taken as objective function. The parameters of the four-parameter random growth method are optimized, the digital core method suitable for complex physical properties of shale gas reservoirs is put forward, and the physical parameters such as porosity, pore detour and inherent permeability of the core are obtained by using lattice Boltzmann method. Comparing with the previous empirical formulas, the correctness of the numerical algorithm is verified. At the REV scale, the lattice Boltzmann model of shale gas percolation is derived, and the gas percolation in organic rich porous media and inorganic pore is simulated, respectively. A characterization unit considering rock matrix and natural fractures is established, and the conclusion that the existence of natural fractures greatly improves the global permeability of shale reservoir is obtained by simulation. It confirms the theory that natural fractures should be communicated as much as possible in high efficiency production of shale gas reservoirs. The results provide theoretical support for the lattice Boltzmann model of shale gas percolation from pore scale to field scale.
【学位授予单位】：西南石油大学
【学位级别】：硕士
【学位授予年份】：2017
【分类号】：TE312

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