Increasing demand for energy around the globe has spurred an interest in exploring unconventional natural resources for oil and gas extraction, particularly from shale. However, the current technology of hydrofracking for shale oil and gas extraction has been challenged by environmental concerns and limited efficiency The increasing use of water for hydrofracking operations and its subsequent water treatment to reduce the heavy metal content prior to safe disposal, would not be sustainable for the long-term. Therefore, the use of CO₂ as an alternative processing fluid has been proposed. The low surface tension of supercritical CO₂ is expected to allow for greater penetration into smaller pore spaces, while the potential reactions of various components within shale with CO₂ (e.g., dissolution and precipitation of mineral phases) may bring about significant morphological changes in shale. The understanding of these physical and chemical changes in the shale reservoir would be very important to consider the use of supercritical CO₂ (scCO₂) during shale oil and gas extractions. Unfortunately, the interfacial behaviors of novel liquid systems of scCO₂-shale systems have not been well characterized. In this study, the alterations in the pore spaces in shales with varying compositions of carbonates, clays, and quartz are investigated at elevated temperatures (T_max = 90 ^oC) and pressures (P_{CO2, max} = 150 atm) which are consistent with in-situ fracking conditions. The corresponding phase changes in shales are reported using Thermogravimetric Analysis (TGA), X-Ray Diffraction (XRD), and micro-tomographic analyses. Our studies showed that shale reacted in the presence of dry scCO₂ at 50 ^oC and P_CO2 = 80 atm had more than a two-fold increase in the pore volume in the micro and mesopores regime. The surface area of shale was found to increase by 20% after it was reacted in scCO₂ at these experimental conditions. Considerable phase alterations were also noted after shale was reacted in scCO₂. TGA analyses showed that the weight loss in the reacted shale sample was about 8% lower compared to unreacted shale, which confirmed the chemical alteration of shale.