腐殖煤干酪根裂解气主生气成熟度上限探讨

烃源岩主生气成熟度上限的确定对含气盆地天然气资源量评价和主生气阶段的确定具有重要的意义。对不同成熟度的15个腐殖煤样开展了生气热解实验和氢、碳、氧元素含量测定,生气热解实验是在800℃高温下进行,结果表明低成熟度煤总产气率最高,随着成熟度的增加,产气率逐渐降低,在Ro为0.6%~2.3%范围内的煤产气率降低幅度很大,从61m3/吨.TOC降到11m3/吨.TOC,在Ro达到2.3%之后煤产气率很低,随着成熟度的增加,产气率缓慢降低。不同成熟度煤的H/C值也呈现相似的变化规律,在Ro<2.3%的煤中,H/C值随成熟度的增加快速降低,在此之后,H/C值缓慢降低,因此,认为Ro=2.3%为腐殖煤的干酪根裂解气主生气成熟度上限。

Discussion on the Maturity Threshold of Primary Kreogen for Cracking Gas Generation from Humic Coal

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%.