分子模拟技术在页岩油气吸附和流动特性研究中的应用进展

Application progress of molecular simulation technology in the study of adsorption and flow characteristics of shale oil and gas

分子模拟技术作为研究纳米尺度下物质行为的关键技术,在页岩油气开采的微观机理研究方面已成为一种重要的研究手段。本文首先概述了分子模拟技术的原理和方法,对页岩储层的常见分子模型进行了总结,对表征页岩油气在储层的分布特征和动力学性质的物理参数如吸附热、吸附能、密度分布、径向分布函数和扩散系数及应用案例等进行了分析;分析总结了温度、压力、孔径、孔壁类型、组分性质对页岩油气吸附特性的影响及机理;重点介绍了分子动力学模拟纳米限域内单相和两相流动中流体黏度变化、黏附和滑移的边界条件导致的流速低于或高于泊肃叶公式预测流速的现象;并对表活剂驱替及渗吸、超临界二氧化碳吞吐页岩油技术中基于分子动力学的微观作用机理进行了阐释。最后总结了分子模拟技术在非常规油气资源开发的优缺点,并提出分子模拟技术在页岩油气领域的未来发展趋势,为非常规油气的开发提供了微观尺度的理论支撑。

Molecular simulation technology,as a key technology to study material behavior at the nanoscale,has become a significant research method in the study of the microscopic mechanism of shale oil and gas extraction.In this paper,firstly,the principle and method of molecular simulation technology were overviewed,the common molecular models of shale reservoir were summarized,and the physical parameters,such as adsorption heat,adsorption energy,density distribution,radial distribution function and diffusion coefficient,which represent the distribution characteristics and dynamic properties of shale oil and gas in reservoir,and their applications were analyzed.The effects and mechanisms of temperature,pressure,pore size,pore wall type and component properties on the adsorption characteristics of shale oil and gas were analyzed and summarized.The phenomenon that the flow velocity is lower or higher than that predicted by Hagen-Poiseuille formula due to the boundary conditions of viscosity change,adhesion and slippage in single-phase and two-phase flows in nanoconfined domains simulated by molecular dynamics was emphatically introduced.The micro-mechanism based on molecular dynamics in surfactant displacement,imbibition and supercritical carbon dioxide huff and puff shale oil technology was also explained.Finally,the advantages and disadvantages of molecular simulation technology in the development of unconventional oil and gas resources were summarized,and the future development trend of molecular simulation technology in the field of shale oil and gas was proposed.The research in this paper provides a micro-scale theoretical support for the development of unconventional oil and gas.