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采用高温高压封闭体系和不同升温速率的实验条件,选用具有不同显微组成和演化程度的煤岩及原始成煤物质泥炭进行了热模拟实验,研究了热解煤层气甲烷碳同位素的演化和沁水盆地煤层气碳同位素动力学特征,发现热解煤层气甲烷碳同位素组成及演化与煤岩的性质和煤化程度、源岩初始演化程度、升温速率等因素密切相关,提出了热解煤层气甲烷碳同位素组成与lg(Ro)之间的关系式,确定了沁水盆地上古生界煤岩生成的甲烷碳同位素演化史及煤层气成因.结果表明:煤岩的初始演化程度低、壳质组含量高、升温速率高的条件下,形成的煤层气碳同位素组成比较轻.样品在不同升温速率形成的热解煤层气甲烷碳同位素组成与lg(Ro)具有良好的正相关关系.沁水盆地上古生界煤岩生成的甲烷碳同位素演化史是随着煤岩的埋藏史,阳城地区太原组、山西组和泥炭热解煤层气甲烷碳同位素基本保持了持续变重的趋势,并且在早白垩世(K1)末都达到最重,之后甲烷碳同位素基本保持不变.首次对成煤物质泥炭进行了碳同位素动力学实验模拟,与煤岩的碳同位素动力学特征进行了对比,表明了泥炭比煤岩具有更轻的碳同位素.将沁水盆地阳城地区二叠系自然煤层气样品的甲烷碳同位素组成与碳同位素动力学研究获得的资料比较研究发现,阳城地区煤层气甲烷碳同位素组成与K1演化至今的煤层气甲烷碳同位素值相近,反映了阳城地区煤层气具有“阶段聚气”的特征.从而反映了甲烷碳同位素动力学是研究煤层气成因的有效方法.
Using the experimental conditions of high temperature and high pressure closed system and different heating rates, thermal simulation experiments were conducted on coal and peat with different microscopic compositions and evolution degrees, and the evolution of methane carbon isotopes in pyrolysis coalbed methane and the evolution of methane It is found that the composition and evolution of methane carbon isotopes in pyrolysis coal beds are closely related to the properties of coal rocks and the degree of coalification, the initial evolution of source rocks and the rate of temperature rise, and so on. The relationship between carbon isotopic composition and lg (Ro) determines the evolution history of methane carbon isotopes and the genesis of coal bed methane in the Upper Paleozoic of Qinshui Basin.The results show that the initial evolution of coal and rock is low, The content of carbon isotope in CBM formed is relatively low under the condition of high content and high heating rate.The methane carbon isotopic composition of pyrolysis coalbed methane formed at different heating rates has a good positive correlation with lg The evolution history of methanogenic carbon isotopes in Upper Paleozoic coal rocks is as follows: the burial history of coal and rock, the Taiyuan Formation, Shanxi Formation and peat pyrolysis coal in Yangcheng area Methane methane isotopes tended to continue to become heavier and heavier, and reached their peak at the end of the Early Cretaceous (K1), after which the carbon isotopes of methane remained basically unchanged. For the first time, carbon isotope kinetics simulations , Which is in contrast with the carbon isotope dynamics of coal and rock, indicating that peat has a lighter carbon isotope than coal and rock.The methane carbon isotope composition and carbon isotope dynamics of Permian natural coal bed methane samples in Yangcheng area of Qinshui Basin A comparative study of the data obtained from the study shows that the methane carbon isotopic composition of the coalbed methane in the Yangcheng area is similar to the methane carbon isotope of coalbed methane so far in the K1 evolution, indicating that the coalbed methane in the Yangcheng area has the characteristic of “stage gas accumulation”. It reflects that the methane carbon isotope kinetics is an effective method to study the genesis of coalbed methane.