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通过组分、同位素特征划分天然气成因类型,结合成藏条件对典型气藏进行解剖,探讨辽河西部凹陷不同成因天然气藏的成藏模式。研究认为,西部凹陷天然气以低熟煤成气和原油菌解气为主,分别以双台子地区和高升地区为典型。双台子地区原生气藏主要为东营期(35Ma)以来,沙三段中上部泥岩热解的煤成气从原油中出溶,或直接经断层运移至浅部聚集而成。高升地区菌解气藏分布于稠油层上方,主要为东营末期(24Ma)以来,原油在生物降解稠化过程中形成的生物气,经短距离运移后就近成藏。
The genotypes of natural gas are divided according to the composition and isotopic characteristics. Typical gas pools are dissected according to the conditions of hydrocarbon accumulation, and the gas accumulation models of natural gas reservoirs with different genetic types in the western Liaohe Sag are discussed. According to the study, natural gas in the western depression is dominated by low-mature coal gas and crude oil-derived bacteria, and is characterized by the Shuangtaizi region and the ascending region respectively. Since the primary gas pool in Shuangtaizi area was mainly Dongying period (35Ma), the coal-derived gas from middle-upper shale pyrolysis of the third member of the Shahejie Formation was dissolved from crude oil or directly accumulated by the fault migration to the shallow part. Biogas reservoirs in the Gaosheng area are distributed above the heavy oil layer, mainly because of the biogas formed during biodegradation and thickening of crude oil since the end of Dongying (24Ma).