过成熟天然气成因鉴别及成熟度判定指标探讨

With the development of natural gas exploration to a deeper level, it was found that the carbon isotope reversal occurred in the mature gas and existed in shale gas and coal gas. However, the discussion of the mechanism of inversion of overgrowth coal is often roughly summarized as the same as shale gas. In addition, the existing identification of coal gas and oil gas causes and maturity of the indicators based on the thermal mechanism of the mechanism, often only applicable to Ro <2.0% of the mature gas, for Ro> 2.0% of the mature gas is no longer mature Be applicable. The above serious restrictions on the identification of genesis and maturity identification in the application of mature natural gas. Based on this study, we study the shale gas samples and coal-to-gas samples with different maturity stages, and analyze their carbon, hydrogen isotopes, components, light hydrocarbon carbon isotopes and components. By comparing these two types of gas And the evolution mechanism of coal formation gas in the mature stage is discussed. In addition, from the geochemical indicators, it is preferable to use the genetic identification index for reversing the gas in the overdue stage. And is preferably used as an indicator for determining the maturity of natural gas in the mature stage. The results can provide scientific basis and guidance for the identification of mature natural gas genesis and maturity.

随着天然气勘探向更深层系拓展，发现过熟气普遍出现碳同位素倒转，且在页岩气中和煤成气中均存在。针对页岩气过熟阶段演化机理的已有较多研究，但对过熟煤成气发生倒转的机理的讨论，则往往粗略归纳为与页岩气相同。此外，现有的鉴别煤成气和油型气成因及成熟度的指标多基于热成因机理，往往只适用于Ro<2.0%的成熟气，对于Ro>2.0%的过成熟倒转气已不再适用。上述严重制约了地化成因鉴别和成熟度判别在过成熟天然气中的应用。基于此，本研究拟选取不同成熟度演化阶段的页岩气样品和煤成气样品，对其碳、氢同位素、组分、轻烃碳同位素和组分进行分析，通过对比这两类气地化指标随成熟度演化规律，探讨煤成气在过成熟阶段发生倒转的成因演化机理。此外，从各项地球化学指标中，优选在过熟阶段仍能用于倒转气的成因鉴别指标。同时优选能用于过成熟阶段天然气成熟度判定的指标。研究结果可为过成熟天然气成因鉴别和成熟度判别提供科学依据和指导。

随着天然气勘探向更深层系拓展，发现过熟气普遍出现碳同位素倒转，且在页岩气中和煤成气中均存在。针对页岩气过熟阶段演化机理已有较多研究，但对过熟煤成气发生倒转的机理的讨论，则往往粗略归纳为与页岩气相同。此外，现有的鉴别煤成气和油型气成因及成熟度的指标多基于热成因机理，往往只适用于Ro<2.0%的成熟气，对于Ro>2.0%的过成熟倒转气已不再适用。上述严重制约了地化成因鉴别和成熟度判别在过成熟天然气中的应用。基于此，本研究选取了不同成熟度演化阶段的页岩气样品和煤成气样品，对其碳、氢同位素、组分、轻烃碳同位素和组分进行分析，通过对比这两类气地化指标随成熟度演化规律，探讨煤成气在过成熟 阶段发生倒转的成因演化机理。经过对比发现，过成熟煤成气碳、氢同位素倒转主要是由于封闭系统芳构化缩聚反应过程形成。此外，从各项地球化学指标中，优选出甲烷碳同位素和甲烷氢同位素作为鉴别过熟阶段倒转气的成因鉴别指标并且在鄂尔多斯盆地得到了良好的应用效果。同时优选了湿度可以作为过成熟阶段天然气成熟度判定的指标。研究结果为过成熟天然气成因鉴别和成熟度判别提供科学依据和指导。