Coupled Fluid Dynamic And Poro-Elastic Effects During Gas Flow In Nanoporous Media: Experiments And Multi-Scale Modelling

该项目将研究气体在微孔/纳米孔介质中传输过程中的流体动力学和孔洞弹性效应，特别是沉积岩。我们将使用一种综合方法，包括在人工和自然微/纳米孔介质上进行气体传输的实验室实验(RWTH亚琛大学)和观察/预期效应的多尺度模拟(清华大学)。这两个合作小组在各自的领域贡献了长期的研究经验，最近开始了成功和富有成效的合作。联合研究针对低渗透岩石中的流体动力学和孔洞弹性变形问题，包括滑移流动、努森扩散、真实气体效应、粘度的压力依赖性、由于输运孔隙系统的变形/修改而导致的渗透系数的应力依赖性，以及气体和水的吸附/解吸与流体流动的相关性。微孔和纳米孔介质的渗透系数并不是一成不变的材料特性，但特别是在用不同的气体测量时，对流体流动测试边界条件的变化(压力、压力梯度、有效应力的变化)非常敏感。通过系统地改变实验条件和使用的气体，可以获得有关孔系统性质的信息。拟议的研究将首先通过使用人工孔系统(纳米毛细管，不同硬度材料中定义的微缝)来阐明气体在狭窄的、可变形的孔中传输的基本关系。随后，将对选定的岩性类型进行测量和评估。更好地理解孔隙大小相关的流变效应和孔隙系统的机械变形之间的相互作用，将极大地提高对不同尺度上的气体流动过程的预测，从而能够从纳米(实验室)尺度提升到公里范围(现场)尺度。虽然许多流体传输模拟方法必须依靠公布的数据来验证其结果，但在拟议的项目中，实验计划将通过建模者和实验者之间的直接反馈而灵活地进行调整。从而保证实验结果的质量和重现性，并验证解释和模型的一致性。

The project will investigate fluid-dynamic and poro-elastic effects during gas transport in micro-/nanoporous media with special focus on sedimentary rocks. We will use a combined approach, involving laboratory experiments of gas transport on artificial and natural micro-/nanoporous media (RWTH Aachen University) and multiscale modeling of the observed/anticipated effects (Tsinghua University). Both partner groups contribute long-term research experience in their respective fields and have started a successful and fruitful co-operation lately.The joint research is targeting issues of fluid dynamics and poro-elastic deformations in low-permeability rocks, including slip flow, Knudsen diffusion, real gas effects, pressure-dependence of viscosity, stress-dependence of permeability coefficients due to deformation/modification of the transport pore system, and dependence of gas and water sorption/desorption on fluid flow. Permeability coefficients of micro- and nanoporous media are not invariable material properties but, particularly when measured with different gases, are very sensitive to changes in the boundary conditions of fluid flow tests (pressure, pressure gradients, changes in effective stress). Information on the pore system properties can be derived by systematic variation of experimental conditions and the gases used.The proposed research will first elucidate fundamental relationships of gas transport in narrow, deformable pores by using artificial pore systems (nanocapillaries, defined micro-slits in materials with different hardness). Subsequently measurements on selected lithotypes will be conducted and evaluated. An improved understanding of the interplay between pore size-dependent rheologic effects and the mechanical deformation of the pore system will greatly improve predictions of gas flow processes on different scales, thus enabling upscaling from the nm (laboratory) to km-range (field) scale. While many fluid transport-modeling approaches have to rely on published data for validation of their results, in the proposed project the experimental program will be adapted flexibly through direct feedback between modelers and experimentalists. The quality and reproducibility of the experimental results will thus be ensured and the consistency of the interpretations and models verified.