云南恩洪向斜煤层重烃异常成因探讨

恩洪向斜煤层重烃气浓度极端异常，但重烃气来源至今不甚清楚。为此，本文通过对恩洪向斜煤样自然解吸阶段的 密集取样和分析测试，对重烃气成因进行了探讨。结果显示，恩洪煤样自然解吸气组分分馏规律明显，重烃气浓度随解吸 时间延长而显著增高；在自然解吸过程中，甲烷碳同位素组成略有变重，重烃气碳同位素组成没有明显变化，烷烃气碳同 位素始终呈现为正碳同位素系列；自然解吸气组分浓度与碳同位素组成之间具有良好的相关关系，但甲烷与重烃气的相关 趋势截然相反。因此，恩洪向斜煤层气主要起源于煤中有机质的热成因，但不排除部分甲烷具有次生生物成因的可能性。

Discussion on Abnomal Heavy Hydrocabon Concentration based on Natural Desorption Process of Coal Samples From the Enhong Syncline, Yunnan

Heavy hydrocarbon gas (HHG) in the coal seam of the Enhong syncline is extremely high in concentration but the gas
source is still unclear. Samples of the gas naturally desorbed from the Enhong’s coal sample was intensively collected and tested
in order to discuss the origin of the abnormal HHG. It was shown that the fractionation of the desorbed gas components is obvious
during the desorption. As the desorption time extends, the HHG concentration becomes obviously higher, the carbon isotope of
the methane becomes heavier. The carbon isotopic composition of the alkane always presents a positive carbon isotope series,
but the carbon isotopic composition of the HHG did not change significantly. Gas component concentration is related well to the
carbon isotopic composition but the opposite trend occurs for the methane and HHG. It was suggested that the CBM in the Enhong
syncline originated mainly from the thermogenic gas of the organic matter in coal but the possibility that the part of the methane is
secondary biogenic can not be excluded.