Keywords: 
• humic coal /
• hydrocarbon generation /
• element ratio /
• maturation threshold

Abstract: It is very significant to determine the maturation threshold of primary hydrocarbon generation of source rock for evaluating the resource quantity of natural gas in gas-bearing basin and determining the primary period of hydrocarbon generation. The authors have done some thermal simulating experiments (at 800℃) on fifteen humic coal samples with different maturity and measured the content of hydrogen, carbon and oxygen elements. The result indicates that total hydrocarbon generation of low maturation coal is high, the amount of the hydrocarbon generation reduce gradually with the increase of maturation, when the value of Ro is between 0.6% and 2.3%, the decreasing scope of hydrocarbon generation is very large, from 61 m³/t·TOC to 11m³/t·TOC, While the value of Ro reach 2.3%, the hydrocarbon generation is very low, it decrease slowly with the increase of maturation. At the same time, we can see the similar variety rule about the value of H/C with different maturation, when the value of Ro is less than 2.3%, the value of H/C decrease fast with the increase of maturation, the value of H/C reduce slowly. So it can be considered that maturation threshold of kerogen cracking gas generation of humic coal is that the value of Ro equal to 2.3%.