塔里木盆地石炭系烃源岩热模拟实验地球化学研究──Ⅰ.气态和液态产物的产率及演化特征

Geochemical Study of Thermal Simulation of Carboniferous Source Rock in the Tarim Basin－I.Yield of gaseous and liquid products and the evolution characteristics

对塔里木盆地石炭系低成熟的泥岩和灰岩生油岩进行了热模拟实验研究。结果表明，气态烃产量随热模拟温度升高呈增加趋势，400℃时开始急剧增加，并且泥岩增加的速度要高于灰岩；气态烃中甲烷、乙烷和氢气组分的产率在400℃时达最大值；甲烷的碳同位素较重，为-37.5‰—-34.0‰；液态烃产率的高峰温度是，泥岩为300℃，灰岩则为350℃，表明灰岩生油高峰滞后。这些资料反映了石炭系泥岩和灰岩具有不同的油气生成演化过程，在生油岩成熟度较低的地区，泥岩生烃无疑是重要的；石炭系烃源岩生成的天然气具有重的碳同位素组成。

In this paper,low mature mudstone and limestone from Carboniferous System in Tarim Basin have been studied by the thermal simulating experiment. The results show that amount of gaseous hydrocarbon become more and more with increasing simulation temperature and begin increasing rapidly at 400℃. The yield of gaseous hydrocarbon at 450℃ is 834. 94m3/tCorg for mudstone and 483. 23m3/tCorg for limestone, indicating that mudstone has higher yield of gaseous hydrocarbon than limestone under the relative high values simulating temperature. The yields of methane,ethane and hydrogen reach the largest at 400℃. The carbon isotopic values of methanes are from - 36. 5‰, to -31. 7‰, for mudstone and from - 37. 5‰, to - 34. 0‰, for limestone. These va1ues show that methanes formed by source rocks from Carboniferous System in Tarim Basin has a heavy carbon isotopic composition. The largest yield of hquid hydrocarbon is 27. 12kg/tCorg for mudstone and 18. 69kg/tCorg for limestone. Their corresponding simulating temperature is 300℃ and 350℃,respectively. This shows that oil-forming high peak value of limestone is higher than that of mudstone. These data reflect that Carboniferous mudstone and limestone have different process of hydrocarbon generation and evolution. Therefore,in the region of distribution of low mature source rock mudstone is important to hydrocarbon generation, and natural gases from Carboniferous source rock should have a heavy carbon isotopic composition.