关键词: 煤炭地下气化, 中—深层煤炭, 燃烧机理, 气化腔扩展演化, 覆岩热变形机理

Abstract: Underground coal gasification can achieve the clean development and utilization of coal resources, which is in line with the low-carbon development strategy of petroleum enterprises and the national carbon peaking and carbon neutrality goals. The paper sketches the current research status of the theory and technology of underground coal gasification, and it is considered that the theoretical system of underground coal gasification has been fundamentally established, the shallow coal underground gasification technology is relatively mature and has not yet become industrialized. The middle-deep coal underground gasification has been preliminarily validated and become the development tendency of underground coal gasification. However, it still faces key challenges such as complex technology, poor basic studies, and stability control in the gasification process. Since 2019, China National Petroleum Corporation Limited has implemented a number of major science and technology projects, which aims to tackle key technologies for coal underground gasification in the middle and deep strata deeper than 800 m. From both theoretical and technical perspectives, this paper summarizes and introduces important progresses and understandings achieved from the implementation of major projects. In terms of basic theory, the understandings of underground coal gasification kinetics, gasification cavity expansion mechanism and overburden thermal deformation mechanism is deepened based on a breakthrough in experimental technique and systematic experimental and simulated studies, laying a theoretical basis for the engineering and process design of middle-deep coal underground gasification. In terms of process technology, a breakthrough has been made in the key core technologies, including gasification resource evaluation and site selection evaluation, gasifier integrity design and control as well as gasification operation control, thus forming the gasifier construction equipment system and underground gasification borehole operation equipment system. In addition, it is proposed to continue to deepen the basic research on middle-deep coal underground gasification and simultaneously promote field tests, so as to improve technology maturity and process stability, and push forward the industrialization of underground coal gasification.

Key words: underground coal gasification, middle-deep coal, combustion mechanism, expansion and evolution of gasification cavity, thermal deformation mechannism of overlying rock