Simulation experiment on the changes of CO₂ burial process in deep coal seam

The injection of carbon dioxide(CO₂)will change the pore fissure structure of coal seam, which has important influence on improving the capacity of CO₂ burial and enhancing methane extraction. In order to explore the evolution law of coal structure after CO₂ injection, the Sihe anthracite and Xinyuan coking-lean coal in Qinshui basin were chosen to do the simulation experiment, through the test and analysis of the coal volume parameter before and after CO₂ treatment, the following conclusions were obtained:CO₂ injection can dissolve minerals in coal, which increases the volume of connected pores and causes the expansion of organic matter; the contribution of mineral dissolution to pore volume changes is not significant, while it leads to the conversion of a large number of closed pores into interconnected pores; the maximum volume increase of pore diameter is larger than 40 μm; the expansion of organic matter is comparatively large and its squeezing effect on pores may reduce the connectivity of coal; the effect of CO₂ injection on coal structure is influenced by coal ranks and simulated burial depth.