The low recovery of oil from tight liquid-rich formations is still a major challenge for a tight reservoir. Thus, supercritical CO₂ flooding was proposed as an immense potential recovery method for production improvement. While up to date, there have been few studies to account for the formation properties’ variation during the CO₂ Enhanced Oil Recovery (EOR) process, especially investigation at the micro-scale. This work conducted a series of measurements to evaluate the rock mechanical change, mineral alteration and the pore structure properties’ variation through the supercritical CO₂ (Sc-CO₂) injection process. Corresponding to the time variation (0 days, 10 days, 20 days, 30 days and 40 days), the rock mechanical properties were analyzed properly through the nano-indentation test, and the mineralogical alterations were quantified through X-ray diffraction (XRD). In addition, pore structures of the samples were measured through the low-temperature N₂ adsorption tests. The results showed that, after Sc-CO₂ injection, Young’s modulus of the samples decreases. The nitrogen adsorption results demonstrated that, after the CO₂ injection, the mesopore volume of the sample would change as well as the specific Brunauer–Emmett–Teller (BET) surface area which could be aroused from the chemical reactions between the CO₂ and some authigenic minerals. XRD analysis results also indicated that mesopore were altered due to the chemical reaction between the injected Sc-CO₂ and the minerals.

This comprehensive review presents a holistic examination of oil shale as a significant energy resource, focusing on its global reserves, extraction technologies, chemical characteristics, economic considerations, and environmental implications. Oil shale, boasting reserves equivalent to approximately 6 trillion barrels of shale oil worldwide, holds substantial potential to augment the global energy supply. Key extraction methods analyzed include surface mining, modified in situ, and true in situ conversion processes, each exhibiting distinct operational parameters and efficiencies. The review further delves into the chemical aspects of oil shale retorting and pyrolysis, highlighting the critical role of variables such as retorting temperature, residence time, particle size, and heating rate in determining the yield and composition of shale oil and byproducts. Economic analyses reveal that capital and operating costs, which vary according to the specific extraction and processing technologies implemented, are crucial in appraising the economic feasibility of oil shale projects. Lastly, the review acknowledges the potential environmental hazards linked with oil shale development, such as groundwater contamination and harmful emissions. It emphasizes the importance of rigorous monitoring programs, environmental impact assessments, sustainable technologies, and innovative strategies like co-combustion and comprehensive utilization systems in mitigating such impacts. The review underlines the need for a balanced approach that harmonizes technological advancement, economic viability, and environmental sustainability in oil shale exploitation.