Transport and Storage Processes in Gas Shales - Information and Insights from Laboratory Experiments

Abstract

Gas and oil shales are heterogeneous, anisotropic, complex multicomponent/multi-mineral systems. It is generally accepted that gas is stored in a dual way: compressed gas in the pore space (“porosity”) gas adsorbed to organic and mineral matter. Organic matter plays a key role in the sorptive storage of gas in carbonaceous shales and many efforts aim at the characterization of the “organic pore system”. In low-TOC shales sorption on clay minerals may become the dominant storage mechanism. During recent years the impact of water - considered to be omnipresent in sedimentary systems - on gas sorption capacity and transport properties has been recognized as another important issue. Experimental research in our group focuses on gas transport and storage processes as a function of effective stress. This includes fluid dynamic issues such as non-Darcy flow regimes (slip flow, molecular diffusion) as well as poro-elastic effects. Pore-volume compressibility of shales and its impact on storage capacity, pore system connectivity and sorption/desorption kinetics under in situ temperature, fluid-pressure and stress conditions. Sorption and fluid transport experiments are conducted in combination to provide clues to the parameters relevant for the quantitative description of these processes and the link between fluid dynamic and poro-elastic controls.