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松辽盆地北部徐深气田探明储量已超过1000×108m3,是中国潜在的一个大气田区.但是,关于深层天然气的成因和来源仍存在较多争议.盆地北部基底浅变质岩分布广泛,是深层天然气的可能气源岩.主要通过对松辽盆地北部基底浅变质岩的热模拟实验,对其生烃潜力及其气态产物地球化学特征进行研究.将取自盆地基底石炭-二叠系浅变质岩在半封闭体系下从300℃加热到550℃进行生烃模拟,温度间隔为50℃,并对每个温度点气态产物进行定量与地球化学分析.实验结果表明:热模拟生成气体烷烃碳同位素组成δ13C1<20‰,δ13C1<δ13C2<δ13C3或δ13C1<δ13C2>δ13C3,表现为高过成熟煤成气的特征;均不具有无机气反序的特征(即δ13C1>δ13C2>δ13C3),与兴城气藏烷烃气碳同位素特征不符,而与取自盆地基底的天然气样碳同位素相近;模拟气体与高过成熟煤成气或油型气混合均不能使烷烃气碳同位素系列反序.浅变质岩具有一定的生烃潜力,相当于烃源岩Ro在2.0%～3.5%范围内,生烃强度为3.0×108～23.8×108m3/km2.
The proven reserves of Xushen gas field in the northern part of Songliao Basin have exceeded 1000 × 108m3, which is a potential gas field in China. However, there are still many controversies about the origin and causes of deep natural gas. The basal metamorphic rocks in the northern part of the basin are widely distributed and are The possible gas source rocks of deep natural gas are mainly studied through the thermal simulation experiments on the basement metamorphic rocks in the northern part of the Songliao Basin, and the hydrocarbon generation potential and the geochemical characteristics of the gas products are studied.From the basement Carboniferous-Permian shallow The metamorphic rocks were heated in a semi-closed system from 300 ℃ to 550 ℃ to simulate hydrocarbon generation at a temperature interval of 50 ℃, and the quantitative and geochemical analyzes of gaseous products at each temperature point were carried out.The experimental results show that the thermal simulation produces alkane carbon The isotopic composition δ13C1 <20 ‰, δ13C1 <δ13C2 <δ13C3 or δ13C1 <δ13C2> δ13C3 showed the characteristics of over-ripened coal gas. All of them did not have the reverse characteristics of inorganic gas (ie δ13C1> δ13C2> δ13C3) The gas and carbon isotope characteristics of alkanes in urban gas reservoirs are not consistent with those of carbon isotopes of natural gas taken from the basement of the basin. Mixing of the simulated gas with the over-mature coal into gas or oil gas can not make the alkane gas carbon isotope Supranuclear metamorphism has the potential for hydrocarbon generation, which is equivalent to that the source rock Ro is within the range of 2.0% ~ 3.5% and the hydrocarbon generation intensity is 3.0 × 108 ~ 23.8 × 108m3 / km2.