ABSTRACT

In order to investigate if pressure can increase the yield of the yield of methane and gaseous hydrocarbon as a whole, both anhydrous and hydrous isothermal pyrolysis experiments were performed on Fushun coal and Kimmeridge shale under pressure of 10 MPa and 50 MPa respectively, and chemical components and stable isotopes of the gaseous products from pyrolysis were analyzed. For both anhydrous and hydrous pyrolysis experiments, Fushun coal and Kimmeridge shale both show lower total gas yields, lower CO₂ yields and lower H₂ yields at high pressure than those at low pressure, but higher total gaseous hydrocarbon yields and higher methane yields at high pressure than those at low pressure. Meanwhile, both Fushun coal and Kimmeridge shale show carbon and hydrogen isotope ratios being heavier at high pressure than at low pressure. However, pyrolysis experiments, theoretical reasoning and carbon and hydrogen isotope analyses proved that pressure can not promote hydrocarbon generation from organic matter, and the increase of hydrocarbon yield is largely due to reaction between carbon dioxide and hydrogen in forming hydrocarbon at high pressure.