Impact of Formation Environment of Coal-Forming Material on Hydrogen and Carbon Isotopic Compositions of Thermogenic Coalbed Gas: Thermal Simulation of Herbaceous Marsh Peats Formed under Different Climatic Environments
Duan Yi
Duan Mingchen
Wu Yingzhong
Yao Jingli
Luo Anxiang
Deng Xiuqin
Qi Yalin
Abstract：The study of coalbed methane (CBM) can provide scientific basis for coalbed methane exploration and development.However,the hydrogen and carbon isotopic compositions of CBM are affected by many factors.Previous studies were mainly concerned with the influence of the properties of gas-forming parent material and maturity on the hydrogen and carbon isotopic compositions of CBM.The influence of formation environment of gas-forming parent material on the isotopic compositions of thermogenic CBM is still unclear.Closed-system isothermal pyrolysis experiments were performed on herbaceous marsh peats derived from high latitude area with cold and dry climates and low latitude area with tropical moist climate.The hydrogen and carbon isotopic compositions and their differences of the hydrocarbon gases (methane,ethane and propane) generated during the pyrolysis of the samples were studied.The results show that the hydrocarbon gases generated from the herbaceous swamp peat in high latitude area had lighter hydrogen and heavier carbon isotopic compositions compared with those in low latitude area.At pyrolysis intervals from peat to vitrinite reflectance values (R o) of 2.5 ％,3.5 ％ and 5.5 ％,the differences in the aver-age δD values between the samples in high latitude and low latitude areas were from-17‰0 to-10‰0 for methane,-32‰ to -28‰o for ethane and-25‰0 to-17‰ for propane,and in the average δ13 C values between them were 2.9‰o to 3.6‰ for methane and 0.9‰o to 1.1‰0 for ethane,respectively.The differences should result from the influence of climatic environment on hydrogen and carbon isotopic compositions of coal-forming original material.The relationship between Ro values and the hydrogen and carbon isotopic compositions of gases generated by coal-forming organic matter under different climatic environments as well as the hydrogen or carbon isotopic relationships of methane and ethane were established.These results may provide a basis for studying on the genesis of coalbed gas formed by coal-forming material under different climatic environments.
Keywords：peatsimulation experimentgas producthydrogen and carbon isotopesclimatic environmentcoalbed gas origingeochemistry
Publication Date：2017-01-01
Online Publishing Date：2025-08-15(First online date of this platform, not the publication date of the document)
Pages：8( 1541-1548 )