Background The CO₂-enhanced coalbed methane recovery (CO₂-ECBM) technology integrates greenhouse gas emission reduction and enhanced CBM recovery, holding great significance for achieving the goals of peak carbon dioxide emissions and carbon neutrality of China and ensuring national energy security. However, due to limitations of insufficient fundamental research and some technical bottlenecks, the engineering application of the CO₂-ECBM technology remains in the engineering test stage. This study reviews the latest advances in research on the mechanisms, evaluation methods, and technical systems of CO₂-ECBM and explores key scientific issues and technical pathways for geological CO₂ storage in coal mine goaves. In combination with representative engineering cases, this study presents a forward-looking analysis of the engineering application prospects and future trends of CO₂-ECBM.

Advances  Regarding the mechanisms behind CO₂-ECBM, the essential theoretical basis of the CO₂ storage and CH₄ production growth in coal seams lies in the synergy between adsorption-based replacement and energy-boosted displacement. A significant theoretical foundation of CO₂-ECBM is continuous fluid migration processes under multi-field, multiphase, and multi-scale coupling, along with their models. Meanwhile, the CO₂ injectivity and its regulatory mechanisms emerge as a prerequisite for engineering-scale deployment of the technology. Many technology systems have been successfully applied to CO₂-ECBM pilot tests and demonstration projects in China, including the five-layer progressive siting and suitability evaluation system, the KUANGDA method for storage capacity estimation, and a range of dynamic reservoir monitoring techniques, such as downhole sensors, tracers, and the transient electromagnetic (TEM) method. Furthermore, the CO₂-ECBM evaluation has shifted from static estimation to the integration of dynamic coupling analysis, accurate engineering prediction, and iterative optimization of technologies. This can be attributed to the CO₂-ECBM engineering prediction and performance evaluation through multi-field coupled numerical simulations, along with innovations and development in air-space-ground-well integrated monitoring systems based on the multi-source data fusion. The engineering applications have been prompted by the development of a liquid/dense-phase CO₂ injection system and the associated vertical well group-based injection-production technical system characterized by the synergy between stepwise intermittent injection increase, coupled with pressure-limited energy-boosted displacement, and intermittent drainage. Achieving stable and efficient supercritical CO₂ injection into horizontal wells through multi-source adaptation, flexible multiphase transport, stepwise pressurization, and intelligent regulation represents the future trend of CO₂-ECBM. Experiments and numerical simulations have been conducted to explore both mineral carbonation within coal-based solid wastes and the reconstruction of stratigraphic sealing in coal mine goaves involved in CO₂ storage. The purpose is to develop a technology integrating CO₂ storage via mineral carbonation and sealing reconstruction, thereby achieving broader engineering applications of CO₂-ECBM.

Prospects  This study proposes that there exist three major technical modes of CO₂-ECBM presently: single-well CO₂ huff-and-puff, CO₂-enhanced fracturing, and CO₂ injection-CH₄ production using vertical/directional well groups. Notably, CBM displacement by supercritical CO₂ using horizontal well groups will contribute to breakthroughs in the large-scale deployment of CO₂-ECBM due to its high injection efficiency and phase stability.