Coal pores are the locations of coalbed
methane occurrence and
enrichment and the main storage space targeted in CO2 sequestration.
The systematic investigation of the coal pore structure and its development
is of great significance to provide insights into coalbed methane
generation, coal mine gas outburst mechanisms, and coal seam CO2 sequestration. In this study, coal pore testing technologies
and methods, pore classification methods, and coal pore structure
characteristics and their main control factors were systematically
investigated and summarized. The results show that direct test methods,
indirect fluid injection test methods, and X-ray and spectroscopic
methods have been used for the quantitative characterization of the
pore structure. However, each testing method has limitations. Therefore,
a comprehensive method for the quantitative characterization of the
full-scale pore structure must be developed, especially for the accurate
quantitative characterization of closed pores in coal. The in situ measurement of pores in coal is one of the future
research trends. Classification methods of pores in coal mainly include
the classification of the genetic pore type, pore size, and pore morphology.
Metamorphism, tectonic deformation, and macerals are the main internal
factors affecting the pore distribution in coal. The effect of tectonic
deformation on the macromolecular structure and micro- and ultramicropores
of coal must be further studied. In addition, molecular mechanics
simulations, molecular dynamics simulations, and quantum chemistry
calculations of the dynamic response of the macromolecular structure
and micro- and ultramicropores during gas adsorption and desorption
must be carried out.