Volcanism is an important controlling factor for organic matter enrichment and sedimentary evolution in proximal continental lakes. Numerous studies have focused on revealing the intrinsic mechanisms of high organic carbon burial regulated by volcanism, while the understanding of the dynamic evolutionary processes of volcanically induced lacustrine depositional systems remains unclear. We integrated core, logging, and geochemical data from more than 20 fully cored wells spanning all sedimentary facies belts of the Chang 7₃, to reconstruct the paleoenvironment and establish sedimentary models during volcanism. By combining sequence stratigraphy, carbon isotope chemostratigraphy, zircon U–Pb dating and astronomical cycle techniques, we established a high-precision isochronous stratigraphic framework, spanning ~241.36 Ma to ~239.7 Ma. This study presented the first detailed record of sedimentary evolution in response to volcanism in the Ordos Basin: Early volcanism led to a transient, relatively dry-cold climate and low weathering intensity; volcanic ash supplied nutrients to the lake, and the accumulation of loose pyroclastics induced overloading and instability of the delta front, triggering slump-type gravity flows. These factors jointly promoted the formation of tuffaceous shale; and sustained volcanism induced a greenhouse effect, resulting in an extremely humid climate and enhanced weathering, thus inducing hyperpycnal flows and appropriate-intensity hyperpycnal flows facilitate felsic shale formation. Furthermore, the climatic background modulated by astronomical cycles amplifies the sedimentary evolutionary responses to volcanism. Multistage siltstone–muddy siltstone assemblages with good reservoir properties, which act as favorable shale oil “sweet intervals”. This study provides new perspectives for understanding the controlling factors of continental lacustrine basin depositional systems and offers guidance for the spatial prediction of shale oil “sweet spots” in the Chang 7₃.

Low-to-medium maturity lacustrine shale oil resources have enormous potential and are projected to play a crucial role in the massive scale-up of crude oil production in China in the near future. The in-situ conversion process is currently the only effective means of utilizing this resource. Nevertheless, significant scientific challenges and technological bottlenecks still exist. Under this circumstance, the National Natural Science Foundation of China approved an integrated project of the Enterprise Innovation and Development Joint Fund titled “The Mechanism of Low-to-medium Maturity Lacustrine Shale Oil Resource Formation and its in-situ Conversion and Exploitation”. This project aims to systematically investigate the entire process of in-situ conversion for low-to-medium maturity shale oil resources and lay a solid scientific and technological foundation for advancing the smooth implementation of on-site pilot trials. This paper presents the latest progress in this field and summarizes the existing scientific and technological challenges that need to be addressed. With the foundational support of the above project, our research team has made significant progress in several fields, including the formation mechanisms of organic matter super-rich shale, low-to-medium maturity shale oil enrichment area evaluation, heat and mass transfer dynamics, coupled fluid field and hydrocarbon expulsion efficiency, exploitation methods, among others. Despite these theoretical advances, several major challenges were identified, which help to further focus on the critical scientific issues, determine the in-situ conversion technique-developing direction, and formulate a feasible implementation plan for future resource utilization.