Petroleum was the most-consumed energy source in the world during the past century. With the continuous global consumption of conventional oil, shale oil is known as a new growth point in oil production capacity. However, medium–low mature shale oil needs to be exploited after in situ conversion due to the higher viscosity of oil and the lower permeability of shale. This paper summarizes previous studies on the process of kerogen cracking to generate oil and gas, and the development of micropore structures and fractures in organic-rich shale formations during in situ conversion. The results show that the temperature of kerogen cracking to generate oil and gas is generally 300–450 °C during the oil shale in situ conversion process (ICP). In addition, a large number of microscale pores and fractures are formed in oil shale formation, which forms a connecting channel and improves the permeability of the oil shale formation. In addition, the principles and the latest technical scheme of ICP, namely, conduction heating, convection heating, reaction-heat heating, and radiation heating, are introduced in detail. Meanwhile, this paper discusses the influence of the heating mode, formation conditions, the distribution pattern of wells, and catalysts on the energy consumption of ICP technology in the process of oil shale in situ conversion. Lastly, a fine description of the hydrocarbon generation process of the target formation, the development of new and efficient catalysts, and the support of carbon capture and storage in depleted organic-rich shale formations after in situ conversion are important for improving the future engineering efficiency of ICP.

A new index named CT-derived carbonation index is proposed to evaluate CO2-induced cement degradation in CO2-rich corrosive environment. This index is obtained by conducting CT scanning of cement samples before and after exposure to CO2, calculating grayscale difference and applying an algorithm to correlate grayscale with CaCO3 content. To demonstrate how to calculate the carbonation index, a CO2-cement interaction experiment along with X-ray computed micro-tomography characterization of a cement sample before and after exposure to CO2 was carried out to investigate the degree of cement carbonation. CO2 was dissolved in 1 wt% NaCl solution under a CO2 partial pressure of 17 MPa and a temperature of 63 °C. The carbonate shell in the cement sample was segmented from the grayscale difference images and the average penetration depth of the carbonate shell was obtained. The carbonation index was then calculated as the ratio of the average penetration depth of the carbonate shell to the radius of the sample, divided by the reaction time. In this study, the carbonation index of the cement sample exposed to CO2 for 14 days was 0.01 day−1. Based on the results in this study and other studies, a carbonation index of 0.05 day−1 or above corresponds to heavy degradation of cement by CO2.