Analysis of the current development status and application prospects of coal reservoir microstructure characterisation technology

Coal reservoirs serve as the primary storage space for coalbed methane (CBM) accumulation and represent key potential sites for CO2 sequestration. A comprehensive understanding of the complex multi-scale pore structure is essential for elucidating gas storage and transport mechanisms across diverse pore types. To systematically map research advancements in coal microstructure characterization, this study analyzed 5074 publications on "coal pore structure methods" from the Web of Science Core Collection using bibliometric approaches. The results reveal three distinct developmental phases: the initial germination stage (pre-2000), the slow development stage (2000–2014) and the rapid growth stage (2014-present). Geographical contributions show China as the most active research nation (2174 publications), followed by the United States (432) and Australia (375). Keyword clustering analysis highlights how evolving research demands have driven technological innovation, with "adsorption," "pore structure," and "permeability" emerging as core themes. Digital imaging reconstruction technologies have enabled a paradigm shift in coal pore structure analysis, from macroscopic investigations to molecular-scale characterization, while also advancing from qualitative descriptions to quantitative or semi-quantitative evaluations. Future priorities center on developing multiscale coupled models that integrate pore structure features with reservoir properties, a critical step for advancing fluid transport predictions in micro-nano pores under complex geological conditions. Characterization technologies for coal reservoir microstructures will play an increasingly vital role in energy development, coal mine hazard control, and environmental protection. Cross-disciplinary collaboration and technological integration will be key drivers of progress in this field.