非常规油气储层多尺度热质传递的细观机理与特性分形分析

Unconventional oil and gas resource is one of the most important succeeding energy sources in the future. The transport process in the reservoir porous media with strong heterogeneity and multi-scale characteristics results from the multiple transport and multi-field coupling effect. However, it is lack of systematic study on the multi-scale pore and fracture structures and heat and mass transfer mechanisms. Therefore, the mesoscopic heat and mass transfer models will be developed in the current project to systematically investigate the multi-scale structural characteristics and transport mechanisms by fractal theory and numerical simulation as well as experimental measurement. The aims of this proposal can be summarized as follows: (1) the statistical fractal scaling laws of the mesoscopic structures will be analyzed in order to establish the quantitative theory and method for the multi-scale pores and fractures of unconventional oil and gas reservoir porous media; (2) a unified mathematical model will be developed to study the transport mechanisms of gas diffusion, slippage flow, seepage flow in micro- and nano-scale pores; (3) a dual-porosity model will be developed for the trans-scale transport in fractured low-permeability porous media in order to construct the quantitative relationship between macroscopic transport properties and mesoscopic structural parameters; (4) the heat-fluid-solid multi-physics model will be developed to explore the effect of stress and temperature on the fluid flow in unconventional oil and gas reservoir. The objective of this project is to develop a complete series of mesoscopic heat and mass transfer theory, models and approaches for unconventional oil and gas reservoir porous media. It is expected that the current project can provide theoretical foundations and technical supports for the exploration and development of unconventional oil and gas resources.

非常规油气资源是未来重要的接替能源，具有强非均质性和多尺度特征，其输运过程是多重效应和多场耦合的结果，但对其多尺度孔裂隙结构及传热传质机理缺乏系统的研究。因此，本项目拟结合分形理论、数值模拟和实验测量，发展非常规油气储层的细观传热传质模型，系统研究其多尺度结构特征和热质传递机理。具体包括：(1)系统研究非常规油气储层微细结构的统计分形特征，建立定量表征多尺度孔隙和裂缝结构的理论和方法；(2)研究微纳孔隙中扩散、滑移和渗流的输运机理，建立描述多种输运机制的统一数学模型；(3)发展裂缝型低渗透多孔介质跨尺度渗流的双重介质模型，建立宏观输运特性和细观结构参数的定量关联；(4)构建非常规油气储层的热流固多场耦合模型，系统研究温度场和应力场对渗流场的耦合作用及规律。通过本项目的研究，建立一套较为完整的研究非常规油气储层的细观传热传质理论、模型和方法，为非常规油气资源的勘探开发提供理论依据和技术支持。

以页岩油气、致密油气和煤层气为代表的非常规油气资源是未来重要的接替能源，研究非常规油气储层的热质传递特性与机理对于非常规油气高效开发和缓解能源压力具有重要的科学意义。本项目围绕非常规油气储层的多尺度结构特征和热质传递特性开展了系统研究，发展了一套较为完整的研究非常规油气储层的细观传热传质理论、模型和方法，为非常规油气资源高效开发提供理论依据和技术支持，进一步丰富和发展多孔介质传热传质理论。. (1)建立了定量表征多孔介质尺度分布、弯曲流线、粗糙表面和分叉拓扑的分形标度律，发展了孔隙累计体积分布和孔隙尺度的分形标度关系，提出了多孔介质迂曲度与孔隙率的定量关系，得到了迂曲度分形维数的显式解析表达式；基于SEM、CT、低场核磁共振以及吸附解吸等实验数据，得到了页岩、煤岩等非常规油气储层的分形特征；结合蒙特卡罗模拟和随机分形方法，发展了重构多尺度多孔介质数字结构的数值算法。. (2)发展了分形毛管束模型、分形孔喉模型、热电模拟模型等多个孔隙尺度物理模型，研究了多尺度多孔介质的单相和多相渗流、达西与非达西渗流、传热与扩散以及电渗流等输运过程，得到了多尺度多孔介质的有效输运特性，建立了多尺度多孔介质微细结构和宏观输运特性的定量关联，提出并研究了多孔介质流体输运和热输运的映射关系。. (3)基于多孔介质有效输运参数的显式表达式，利用有限元方法求解宏观热质输运方程，构建了一种计算跨尺度输运和热流固耦合的高效方法，建立了介质微观结构和性质与宏观特性的定量关系；根据裂缝尺度分布的分形标度律建立了裂缝型多孔介质的渗流和热流固耦合模型，揭示了裂缝结构、温度场和应力场对于渗流场的影响机理。. .