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.

Deep and ultra-deep petroleum resources have become major contributors to petroleum reserves. The Tarim Basin has recently witnessed discoveries of several oil reservoirs at depths exceeding 8000 m, which extend the exploration depth limit for crude oil and light oil resources. To clarify the role of overpressure during the critical stage of crude oil cracking (Easy Ro ≈ 1.0–2.0%), this study conducted low-temperature, long-duration, overpressure (150 MPa) gold tube pyrolysis experiments on marine crude oil from the Tarim Basin. Comprehensive analysis of the cracking products (C₁–C₃₀₊) revealed significant differences in the thermal stability and cracking behavior of hydrocarbon molecules with different chain lengths: long-chain hydrocarbons (C₁₂₊) were continuously consumed as the primary reactants, whereas short-chain hydrocarbons (C₆–C₁₂) initially formed as products and subsequently underwent secondary cracking as reactants. During this process, overpressure played a critical role in delaying the yield peak of light hydrocarbons and suppressing their secondary cracking. This mechanism resulted in a slower increase in gaseous hydrocarbon yield under overpressure conditions, and the carbon isotopic composition clearly recorded a shift in the cracking precursors from heavy to light hydrocarbons. Furthermore, fluorescence lifetime, as a sensitive spectroscopic indicator, exhibited delayed decay under overpressure, confirming the inhibition of aromatization and polymerization reactions by overpressure. By illuminating the sequential nature of hydrocarbon cracking and the moderating influence of overpressure at molecular and spectroscopic levels, this work offers crucial evidence for understanding multi-phase hydrocarbon coexistence and forecasting the preservation depth of discrete-phase crude oil in the Shuntuoguole area.