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裂谷盆地岩浆活动强烈,其中侵入岩区的天然气资源丰富且天然气性质异常。为深入研究侵入岩区的天然气成因,对沾化凹陷孤北地区天然气和气源岩的地球化学特征进行了系统分析。结果发现,孤北地区侵入岩区的气源岩过成熟,天然气中无机成因二氧化碳和硫化氢含量较高、烷烃碳同位素较重、天然气性质变化较大。结合天然气成因和同位素分馏理论分析,认为造成天然气性质异常的原因是侵入岩区气源岩除经历正常的热演化作用外,还受到岩浆及岩浆流体的高温烘烤作用,导致有机质发生多阶演化、多次生烃以及碳酸盐岩(或硫酸盐)分解;岩浆流体混入也使天然气组成进一步复杂化。侵入岩区天然气不仅具有普遍混合性,而且具有多重(多源、多阶、多期及烃类气体与非烃类气体)混合性;由于混合类型及混合比的不同,导致天然气性质存在明显差异。
The rift basin has strong magmatic activity, in which the natural gas in the intrusive rock area is abundant and the natural gas is abnormal in nature. In order to study the genesis of natural gas intruded into the rock area, the geochemical characteristics of natural gas and source rock in the Gubeiku area were systematically analyzed. The results show that the gas source rocks in the intrusive rocks in the Gubei area are over matured. The content of inorganic carbon dioxide and hydrogen sulfide in the natural gas is high, the carbon isotopes of the alkanes are heavy, and the nature of the natural gas changes greatly. Based on the analysis of gas genesis and isotopic fractionation theory, it is considered that the reason for the abnormal nature of natural gas is that, besides experienced normal thermal evolution, gas source rocks in intruded rock are also subject to high temperature bake of magmatic and magmatic fluids, resulting in multi-order evolution of organic matter , Multiple hydrocarbon generation, and carbonate (or sulfate) decomposition; the inclusion of magmatic fluids further complicates the natural gas composition. The natural gas intruded into the rock area is not only mixed universally, but also has multiple (multi-source, multi-stage, multi-stage and hydrocarbon gas and non-hydrocarbon gas) miscibility; due to the different mixing types and mixing ratio, natural gas has obvious difference .