油伴生CO_2气的成因及其石油地质意义

Genesis of oil-associated CO_2 and its significance in petroleum geology

以松辽盆地南部油伴生CO2气为研究对象,通过组分分析及碳、氧及氦同位素分析,结合中国已有伴生CO2气的含量及同位素数据,研究油伴生CO2气的成因及其意义。结果表明:中国油伴生气中CO2的含量为0～99.53%,大部分在5%以下;油伴生CO2气的δ13CCO2值为-15.91‰～+6.49‰,集中分布于-13‰～-4‰,以无机成因气为主;松辽盆地南部油伴生CO2气的含量为1.43%～54.22%,δ13CCO2值为-5.32‰～-6.76‰,为幔源-岩浆成因;幔源-岩浆成因油伴生CO2气与气藏中的CO2气成因一致,注入时间一般晚于油气大规模充注时间,CO2充注驱油普遍存在;在幔源-岩浆CO2与油气混合成藏地区(如松辽盆地南部)寻找幔源-岩浆CO2充注驱油成因的次生油气藏将是一个新的勘探思路。

Taking the oil-associated CO2 samples from southern Songliao Basin as the research object,the genesis and significance of the oil-associated CO2 were studied through component analysis,carbon,oxygen and helium isotopic analysis and combining with the existent oil-associated CO2 content and isotopic data in China.The results show that the CO2 content of oil-associated gas in China is 0-99.53%,most of which is less than 5%.Carbon stable isotopic value for CO2 ranges from-15.91‰ to 6.49‰,which mainly distributes in the section of-13‰ to-4‰,indicates that most of CO2 has an inorganic origin.The content and the carbon stable isotopic value for the oil-associated CO2 in southern Songliao Basin range from 1.43% to 54.22% and-5.23‰ to-6.76‰,respectively,suggesting a mantle-magmatic origin.As the oil-associated CO2 and CO2 in gas reservoir had the same origin,and the injected-time for oil-associated CO2 was later than the large scale oil and gas generation.The CO2 flooding was common in geologic history.In the mixed-reservoir contained mantle-magmatic CO2 and oil,such as the southern Songliao Basin,secondary oil and gas reservoirs could be found with the function of the displacement of CO2.