## 7 Conclusions  
Oil shale represents a significant, yet largely untapped, energy resource that holds considerable potential to meet global energy needs. This review has sought to provide a comprehensive overview of the current state of oil shale technology, including exploration and extraction methods, chemical characteristics, economic considerations, and environmental impacts. The multifaceted nature of oil shale development necessitates a holistic approach that balances technological advancements, economic viability, and environmental sustainability.  
* Reserves and distribution: Oil shale is a widespread resource, with major deposits found globally. Estimates suggest that the world's total resources of oil shale are equivalent to 6 trillion barrels of shale oil, with the largest reserves situated in the United States, China, and Russia. The vastness of these resources underscores oil shale's potential to contribute significantly to the global energy supply;
* Extraction technologies: The extraction technologies employed for oil shale have evolved over time, reflecting the industry's progress and adaptability. Conventional mining, modified in situ conversion, and true in situ conversion represent key methods, each with their unique operational parameters, strengths, and limitations. However, these techniques are continually subject to improvement and innovation, with future advancements expected to further enhance efficiency;
* Chemical characteristics: Oil shale retorting and pyrolysis are central to the conversion of kerogen into usable hydrocarbons. Key parameters influencing these processes include retorting temperature, residence time, particle size, and heating rate. These factors, in turn, determine the yield and composition of shale oil and other products.  
Future research can further optimize these parameters for improved yield and product quality;
* Economic analysis: The costs associated with oil shale development are primarily divided into capital and operating costs, which vary depending on the specific extraction and processing technology employed. Understanding these costs and their implications is vital for assessing the economic viability of oil shale projects;
* Environmental impacts and mitigation: The extraction and utilization of oil shale can lead to significant environmental pollution, particularly through potential groundwater contamination and harmful emissions. Implementing rigorous monitoring programs, environmental impact assessments, and sustainable technologies can help mitigate these impacts. Innovative strategies, like the co-combustion of oil shale with high sulfur fuel and comprehensive utilization systems, have also shown promise in reducing pollution.  
In summary, oil shale offers promising prospects for energy production. However, its development necessitates careful balancing of technological advancements, economic considerations, and environmental sustainability. With continued research and innovation, oil shale has the potential to become a significant contributor to the global energy landscape. Nevertheless, achieving this potential will require a commitment to best practices, responsible stewardship, and a focus on sustainability.  
Conceptualization, B.J. and J.S.; investigation, B.J. and J.S.; writing, B.J. and J.S.; validation, B.J. and J.S.; investigation, J.S.; resources, B.J. and J.S.; supervision, B.J. and J.S. All authors have read and agreed to the published version of the manuscript.  
State Center for Research and Development of Oil Shale Exploration open fund (No. 33550000-22-ZC0613-0249) and the Science Foundation of China University of Petroleum, Beijing (2462021 QNX2004).  
Not applicable.  
The data that support the findings of this study are available from the corresponding author upon reasonable request.  
The authors declare no conflict of interest.