Abstract: Accurate prediction of coal rock fracture conductivity in different production stages is essential for efficient development of coal⁃ rock gas. However, gas⁃measured conductivity of artificial fractures in deep coal rocks has been rarely studied. Considering flows of various phases in fracture⁃filled layers in coal rocks, together with the development patterns of deep coal⁃rock gas in eastern Ordos Basin, this study conducted conductivity tests under different sanding concentrations and closure pressure. The results show that the gas⁃measured fracture conductivity of coal rocks is 1.2-10.3 times the liquid⁃measured fracture conductivity, and the disparity widens as the closure pres⁃ sure increases. Owing to low strength of coal rocks and prevalence of natural fractures, the conductivity loss at low closure pressure is gov⁃ erned primarily by proppant compaction and embedment, which together account for more than 60% of the total loss. When the closure pressure exceeds a critical range of approximately 20-30 MPa, the proppant crushing intensifies significantly, and it becomes a more domi⁃ nant mechanism impairing the fracture conductivity. Moreover, prediction models for gas/ liquid⁃measured fracture conductivity of deep coal rocks were established based on the dimensional analysis theory. These models yield results in good agreement with experimental data and field observations, with a mean error below 8% for liquid measurements and below 4% for gas measurements. 

Key words: Ordos Basin, deep coal?rock gas, conductivity prediction, gas measurement, liquid measurement, dimensional analysis