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

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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.