The characters and quality of natural gases is changeful in many geological progresses, including primary migration, diffusion, water washing, bacterial activity. In addition, hydrologic setting and secondary processes also influence composition of coalbed gas.
在初次运移、扩散、水洗等各种后生、次生作用过程中，天然气的特征和数量会发生变化。此外，水动力等地质条件和次生作用等也影响着煤层气的组成。