Objective Tar-rich coal, a type of unique unconventional oil and gas resource that integrates coal, oil, and gas, can be transformed into tar, combustible gases, and semi-coke solid fuels with high added value through in-situ pyrolysis. Therefore, the in-situ pyrolysis of tar-rich coal has the potential to meet the challenges in achieving the green exploitation and clean, low-carbon utilization of coals in the traditional coal industry. Furthermore, in terms of how to reduce coal pollution emissions and enhance energy efficiency, this technology offers a new solution for attaining the goals of peak carbon dioxide emissions and carbon neutrality. It also represents an important reference for China to make a breakthrough in strategic dependence in terms of oil and gas resources. However, merely limited pioneering experimental studies have been conducted on the in-situ underground pyrolysis of tar-rich coal in China. Therefore, there is an urgent need to conduct research on the responses of geological environments to the in-situ pyrolysis of tar-rich coal and to explore comprehensive, life-cycle geological guarantee technologies.

Methods Based on the characteristics of disturbance to geological environments as their responses to the in-situ pyrolysis, this study highlighted the effects of the in-situ pyrolysis on rock mass metamorphism, the damage and deformations of overburden, disturbance to groundwater, surface subsidence, and surface ecosystem within the pyrolysis zone. A summary was given on the primary aspects and testing techniques for the geological condition assessment and process monitoring for the in-situ pyrolysis of tar-rich coal, presenting the challenges in the geological guarantees for the in-situ pyrolysis. By integrating insights into theoretical research, technical methods, sensing devices and units, data interpretation, multi-source information fusion, and practical engineering, this study presented reflections on the construction of a geological guarantee technology system for the in-situ pyrolysis of tar-rich coal.

Results and Conclusions This study concludes that under the novel resource transformation and utilization model—the in-situ pyrolysis of tar-rich coal, there is an urgent need to develop supported geological guarantee technologies, as well as comprehensive methods and standards for the development, design, construction, and evaluation of the technologies, with the purpose of normalizing and guiding the development and applications of technologies for the tar-rich pyrolysis of tar-rich coal. Additionally, it is necessary to actively promote innovations in R&D of technologies for the clean utilization of tar-rich coal, as well as enhancing relevant safety production standards and driving the profound integration with ecological protection measures. These efforts are aimed at providing comprehensive strategic countermeasures and guarantees for the green transformation and efficient, sustainable development of the coal industry.