Characteristics and kinetic of coal pyrolysates with different thermal simulation apparatuses

Coal samples from the Shahezi Formation in the Songliao Basin were pyrolyzed by means of Rock-Eval II, TG-MS (thermogravimetry-mass spectrometry) and gold tube apparatuses, respectively, in order to investigate characteristics and kinetic behaviors of their pyrolysates. Comparative results of pyrolysate yields revealed that the Ro corresponding to methane generation under TG-MS apparatus conditions was close to the maturity value of gaseous hydrocarbons generated under geological conditions, while the maturity of methane generation under Rock-Eval II experiment conditions was much lower than the Ro corresponding to gaseous generation under geological conditions. The termination temperature of methane generation from the coal sample under the TG-MS experiment was about 850??C (at a heating rate of 10??C/min), and the corresponding Ro was about 5.3% calculated with the extended Easy Ro% model. However, the C1-5 mass yields increased all the time while even at the terminal temperature in the gold tube experiment (with the corresponding Ro of 4.9%, at a heating rate of 2??C/hour and the terminational temperature is about 650??C), indicating a gas-generative potential of the coal sample at higher maturity and the primary cracking of organic matter as the major source of methane in a closed system at this high temperature stage. It might be the recombined reaction of C6+ liquid hydrocarbons with kerogen or bitumen in a closed environment that formed some new products with high thermal stability, which then generated methane at even higher temperature stage. For an open system, such as in the TG-MS experiment and Rock-Eval experiment, this recombined reaction could not take place because C6+ liquid components were removed immediately with the carried gas. The geological application of kinetic parameters of gas generation from coals in the Xujiaweizi area showed that a great difference existed in the extrapolation of kinetic parameters obtained from different pyrolyzed apparatuses. Based on these data, the TG-MS apparatuses was recommended to simulate the simultaneous generation and expulsion process of hydrocarbons under geological conditions, while the gold tube apparatus was suitable for simulating a gas generation process of secondary cracking of hydrocarbons in the closed system.EI05806-8143