论文部分内容阅读
为了系统认识四川盆地陆相天然气地球化学特征及差异,利用天然气组分、碳同位素与轻烃等地球化学资料,对四川盆地不同地区不同层位陆相天然气地球化学特征进行分析及对比,探讨其差异成因。结果表明,四川盆地陆相天然气地球化学特征在横向与纵向均存在较大差异。横向上,川西地区天然气甲烷含量与干燥系数均高于川中地区,川西地区天然气以干气为主,川中地区天然气以湿气为主,地层厚度、埋深及气源岩的不同是造成上述差异的主要原因。不同地区的天然气组分特征参数纵向变化规律也明显不同,川西地区该变化规律主要受烃源岩成熟度与天然气运移分馏影响,而川中地区则主要受烃源岩成熟度及类型的影响。四川盆地陆相天然气以成熟气与高成熟气为主,仅川中地区侏罗系天然气以成熟气为主,川西地区天然气成熟度最高,川中地区与川南地区上三叠统次之,川中地区侏罗系最低,烃源岩埋深与厚度的差异造就了上述成熟度差异。四川盆地陆相天然气以煤型气为主,同时存在一定的油型气,不同地区油型气的含量、分布、成因与来源均存在较大的差异:川西地区仅须二段存在少量油型气,来自马鞍塘组—小塘子组生成的石油裂解;川中地区侏罗系以油型气为主,来自侏罗系干酪根裂解;川南地区须家河组有一定的石油裂解成因油型气,主要来自下伏气藏。四川盆地上三叠统天然气以水溶相与游离相运移,而侏罗系天然气则主要以游离相运移。
In order to systematically understand the geochemical characteristics and differences of terrestrial natural gas in Sichuan Basin, the geochemical characteristics of terrestrial natural gas in different strata of Sichuan Basin were analyzed and compared using geochemical data of natural gas components, carbon isotopes and light hydrocarbons, Difference causes. The results show that the geochemical characteristics of continental gas in the Sichuan Basin are quite different in horizontal and vertical directions. In horizontal direction, natural gas methane content and drying coefficient in western Sichuan are higher than those in central Sichuan, natural gas in western Sichuan is mainly dry gas, and natural gas in central Sichuan is mainly moisture. The differences in formation thickness, depth and gas source rock cause these differences The main reason. The vertical variation of the characteristic parameters of natural gas components in different regions is also obviously different. The variation in western Sichuan is mainly affected by the maturity of source rock and the migration and fractionation of natural gas, while the central Sichuan is mainly affected by the maturity and type of source rock. The natural gas in the Sichuan Basin is mainly composed of mature gas and high mature gas. Only the Jurassic natural gas in the central Sichuan region is mainly mature gas, and the natural gas in the western Sichuan region has the highest maturity. The Middle Triassic in the Central Sichuan Basin and the South Sichuan Basin are the second, Luo system is the lowest, source rock depth and thickness of the difference between the maturity of the difference. In the Sichuan Basin, the natural gas in the Sichuan Basin is dominated by coal-type gas, and at the same time there is a certain amount of oil-type gas. The content, distribution, origin and origin of oil-gas in different regions are quite different: Gas from the Ma’antang Formation to the Xiaotangzi Formation. The Jurassic in the central Sichuan area was dominated by oil-type gas and came from the Jurassic kerogen cleavage. The Xujiahe Formation in the southern Sichuan area had some petroleum-cracking oil type Gas, mainly from the underlying gas reservoir. The Upper Triassic natural gas in the Sichuan Basin migrated as a water-soluble phase and a free phase while the Jurassic natural gas migrated mainly as a free phase.