Research progress on catalysts for in-situ upgrading of medium-low maturity shale oil: A comprehensive review

Medium-low maturity (MLM) shale oil represents a significant unconventional hydrocarbon resource. In-situ catalytic conversion technology has emerged as a pivotal method for the large-scale extraction of deep shale oil reservoirs. This review systematically summarizes the pyrolysis mechanisms of MLM shale oil, thereby providing a theoretical foundation for catalyst design. It comprehensively examines research progress on both solid and liquid catalysts. Solid catalysts include transition metal salts, zeolites, and metal-supported catalysts, while liquid catalysts encompass systems such as water-soluble, oil-soluble, ionic liquid, and microemulsion types. The advantages and disadvantages of various catalysts under in-situ reservoir conditions are compared and analyzed. Solid catalysts exhibit high activity but face challenges in reservoir migration and diffusion. Conversely, liquid catalysts improve mobility but require enhancements in reducing costs and increasing activity. The economic feasibility and environmental impact of existing catalysts are also evaluated. Finally, considering current challenges in the industrial application of catalysts for shale oil conversion, future research directions and priorities are proposed. This review aims to establish a technical foundation for the efficient catalytic conversion of MLM shale oil.