Experimental Investigation of Geochemical Interactions between Supercritical CO₂ and Shale

The geochemical interactions between shale, supercritical carbon dioxied (SC-CO₂ ), and brine play a significant role in determining both the possibility of carbon storage and the long-term stability of shale gas reservoirs. The shale samples were exposed to CO₂-brine-rich environments for a period of 30 days to simulate the in-situ conditions of the shale reservoirs. The pre- and post-analysis were conducted to identify changes in mineralogy, chemical bonding, pore structure, surface texture and morphology. Several analytical techniques, including X-ray diffraction (XRD), thermogravimetric analysis (TGA), Fourier transform infrared spectrometry (FTIR), scanning electron microscopy (SEM), and low-pressure gas adsorption (LPGA), were used for characterisation. The results show that significant mineralogical changes occurred to clay minerals and carbonate, accompanied by modification in hydrocarbon functional groups and fluctuation in micropore and mesopore parameters. The consistent variations in pore characteristics are attributed to continuous processes of dissolution- precipitation and development of increased surface roughness due to reaction. The formation of microfractures and the etching effect of the samples were studied using high-resolution SEM images. TGA study confirmed the systematic mass loss caused due to prolonged reactions. These findings indicate that the reservoir integrity and the storage capacity can be affected due to pore structure evolution during geological CO₂ sequestration. Additionally, the changes documented in this study can provide the pathway to improve shale gas recovery, signifying the crucial role of shale formation in global decarbonization efforts