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

Applicant Professor Dr. Ralf Littke, since 7/2020
Subject Area Palaeontology
Mineralogy, Petrology and Geochemistry
Geophysics
Physical Chemistry of Molecules, Liquids and Interfaces, Biophysical Chemistry
Fluid Mechanics
Theoretical Chemistry: Molecules, Materials, Surfaces
Term from 2018 to 2021
Project identifier Deutsche Forschungsgemeinschaft (DFG) - Project number 392108477
 
Final Report Year 2021

Final Report Abstract

Fundamental aspects of gas transport in selected micro- and nanoporous materials (artificial and natural) were investigated jointly by experimental measurements and numerical modeling. Close co-operation of the partner institutes ensured feedback between experimentalists and modeler in terms of adjustment of experimental (starting and boundary) conditions, quality control, identification of first-order effects and dismissal of inadequate data or modeling concepts. • Within the range of Knudsen numbers covered by this study, complex 2nd and higher order fluiddynamic (slip-flow) models for gases were not required. In a geotechnical context, this finding can be instrumental in estimating fluid flow regimes and predicting production rates. • Permeability measurements with CO2 close to its critical point involve uncertainties related mainly to strong fluctuations in isothermal compressibility and, to a lesser extent, viscosity. The uncertainties may be reduced by improved experimental procedures (temperature control), but these improvements are not expected to be of much relevance for geotechnical applications. • Flow experiments with CO2 in this study were performed on dry samples, but since natural, geologic systems of interest always contain water, the adsorption of water and its effect on apparent and effective permeability requires further research. • Traditional/conventional fluid flow concepts should be reviewed and reassessed by direct and close co-operation of experimentalists and modeling specialists. The quality of literature data is often difficult to assess and misinterpretations may occur due to lack of communication between experimentalists and modelers. • A comprehensive experimental dataset could be established documenting an increase in apparent permeability at constant effective stress (Terzaghi definition) upon mechanical compression of a tight sandstone sample with significant clay content. This effect is attributed to widening (extension) of clay-coated transport pores in “pressure shadows”. • Two-phase flow experiments on a tight sandstone showed that the transport processes are controlled by viscous and slip flow up to a water saturation of 35-38%, whereas at water saturations >52% capillary-pressures affect the gas flow.

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