Image-based micro-continuum model for gas flow in organic-rich shale rock
Image-based micro-continuum model for gas flow in organic-rich shale rock
复制标题
DOI：
10.1016/j.advwatres.2018.10.004
复制
发表时间：
2018-12-01
影响因子：
4.7
通讯作者：
Tchelepi, Hamdi A.
中科院分区：
文献类型：
--
作者：
Guo, Bo;Ma, Lin;Tchelepi, Hamdi A.
控制富含有机物页岩流动动力学的物理机制尚不清楚。挑战包括纳米级孔隙和成分空间分布的多尺度异质性。最近，数字岩石物理（DRP）使用岩石样本的高分辨率图像作为流动模拟的输入，已被用于页岩。页岩图像的一个重要问题是亚分辨率孔隙度（低于仪器分辨率的纳米孔隙），这对仪器和计算模型提出了严峻的挑战。在这里，我们提出了一个基于 Darcy-Brinkman-Stokes 框架的微连续体模型。该方法使用可以独立测量的基于物理的参数来耦合已解析的孔隙和未解析的纳米多孔区域。斯托克斯方程用于解析孔隙。未解析的纳米多孔区域被视为连续体，并采用考虑滑流和克努森扩散的渗透率模型。还考虑了有机物中的吸附/解吸和表面扩散。我们应用我们的模型来模拟页岩高分辨率 3D 分段图像中的气流。结果表明，样品的总体渗透率（在固定压力下）取决于时间尺度。早期渗透率由斯托克斯流控制，而晚期渗透率由非达西效应和表面扩散控制。
The physical mechanisms that control the flow dynamics in organic-rich shale are not well understood. The challenges include nanometer-scale pores and multiscale heterogeneity in the spatial distribution of the constituents. Recently, digital rock physics (DRP), which uses high-resolution images of rock samples as input for flow simulations, has been used for shale. One important issue with images of shale rock is sub-resolution porosity (nanometer pores below the instrument resolution), which poses serious challenges for instruments and computational models. Here, we present a micro-continuum model based on the Darcy-Brinkman-Stokes framework. The method couples resolved pores and unresolved nano-porous regions using physics-based parameters that can be measured independently. The Stokes equation is used for resolved pores. The unresolved nano-porous regions are treated as a continuum, and a permeability model that accounts for slip-flow and Knudsen diffusion is employed. Adsorption/desorption and surface diffusion in organic matter are also accounted for. We apply our model to simulate gas flow in a high-resolution 3D segmented image of shale. The results indicate that the overall permeability of the sample (at fixed pressure) depends on the time scale. Early-time permeability is controlled by Stokes flow, while the late-time permeability is controlled by non-Darcy effects and surface-diffusion.