3 Search Results

Carbon Storage TRS

We studied the effects of supercritical carbon dioxide (scCO₂) on the matrix permeability of reservoir rocks from the Eagle Ford, Utica, and Wolfcamp formations. We measured permeability using argon before exposure of the samples to scCO₂ over time periods ranging from days to weeks. We measured permeability (and the change of permeability with confining pressure) when both argon and scCO₂ were the pore fluids. In all three formations, we generally observe a negative correlation between initial permeability and carbonate content—the higher the carbonate content, the lower the initial permeability. In clay- and organic-rich samples, swelling of the matrix resulting frommore » adsorption decreased the permeability by about 50% when the pore fluid was scCO₂ although this permeability change is largely reversible. In carbonate-rich samples, dissolution of carbonate minerals by carbonic acid irreversibly increased matrix permeability, in some cases by more than one order of magnitude. This dissolution also increases the pressure dependence of permeability apparently due to enhanced mechanical compaction. Despite these trends, we observed no general correlation between mineralogy and the magnitude of the change in permeability with argon before and after exposure to scCO₂. Flow of scCO₂ through μm-scale cracks appears to play an important role in determining matrix permeability and the pressure dependence of permeability. Extended permeability measurements show that while adsorption is nearly instantaneous and reversible, dissolution is time-dependent, probably owing to reaction kinetics. Our results indicate that the composition and microstructure of matrix flow pathways control both the initial permeability and how permeability changes after interaction with scCO₂. Electron microscopy images with Back-Scattered Electron (BSE) and Energy Dispersive Spectroscopy (EDS) revealed dissolution and etching of calcite minerals and precipitation of calcium sulfide resulting from exposure to scCO₂.« less

In this work, we probed the physical and chemical alteration of the carbonate-rich Utica Shale following CO₂ exposure when thin films of water were present at the shale surface. All reaction conditions were examined at 40 °C and CO₂ pressures up to 10.3 MPa for 14 days. CO₂ dissolution in the water layer at 2342 cm^-1 and carbonate dissolution and precipitation at 1424, 874, and 712 cm^-1 were discerned with in-situ Fourier Transform infrared spectroscopy (FT-IR). Significant etching and pitting from exposure to CO₂ and water were observed with feature relocation scanning electron microscopy (SEM). Application of the density functionmore » theory (DFT) for pore size analysis showed that micropores between approximately 0.9 and 2 nm disappeared while the mesopore volume increased after dissolution of carbonate. These results may provide new insights that carbonate rich shales such as the Utica may have a greater potential for alterations of pore space due to the reactivity of CO₂ which may affect 1) how CO₂ storage in shale formations plays a role in Carbon Capture and Storage (CCS) activities, 2) if CO₂ can be utilized as a potential fracturing agent, and 3) whether CO₂ is an effective fluid for enhanced hydrocarbon extraction.« less