Author(s)

Wenping Jiang, Shaoyong Song

Corresponding Author

Wenping Jiang

Abstract

In view of the problems such as the great difference of CBM content in different coal ranks in our country and the unclear understanding of the control mechanism, the gas content test data of surface drilling coal seam coring in dozens of representative areas in China are sorted out. The characteristics of methane content and gas composition under ashless drying conditions of different rank coals are summarized. According to the maximum reflectivity of vitrinite (0.5%, 1.30%, 2.50%, 3.75%), the relationship between methane content and deterioration degree was divided into five stages. The methane content at each stage showed the characteristics of low–rapid increase–slow increase–peak–rapid decrease. The production characteristics of C2+ , H2O, CO2, CH4 and H2 at different temperatures were analyzed by means of thermal simulation experiment and pyrolysis infrared spectrum experiment. Based on the characteristics of CH4 generation, the whole process of gas generation was divided into six stages according to the temperature from low to high. It mainly includes the first phase of adsorption and physical precipitation of the absorption state, and the other five stages of chemical reaction formation. Based on the relationship between vitrinite reflectance and experimental temperature during heating, the relationship between the generation intensity of CH4 and the content of CH4 in the coal seam is discussed. It is inferred that the intensity of CH4 generation in different metamorphic stages is the main controlling factor of CH4 content distribution with metamorphic degree.

Keywords

Coalbed Methane(CBM); Gas Content; Gas Composition; Coal Metamorphic Degree; Generation Intensity