四川盆地烃类垂向微运移及其地球化学效应

HYDROCARBON VERTICAL MICRO-MIGRATION AND ITS GEOCHEMICAL EFFECTS IN SICHUAN BASIN

根据钻井垂向剖面中烃类的变化特征,研究其烃类垂向微运移迹象,用以追溯地表异常来源,进而研究近地表异常模式及成因机理。四川盆地油气井中自深至浅,环烷烃百分组成逐渐降低,正构和异构烷烃不断增加;280 nm和210 nm紫外导数值逐渐降低;运移指向明显,表征了烃类垂向微运移客观存在的事实。川西地区近地表样品与下伏储层C1—C5色谱图及三维荧光图谱基本相似,说明二者同源,揭示了近地表化探异常为“有源之水”,近地表化探异常及其靶区预测是可靠的。

According to the characteristics of the hydrocarbons in the well profiles, the hydrocarbon vertical micro-migrating tracks can be revealed and then proceed to trace to the source of hydrocarbon anomalies near surface. This is an important method of studying the near-surface hydrocarbon anomaly patterns and forming mechanism. In the oil and gas wells in Sichuan Basin, the percentage of naphthenic hydrocarbon gradually decreased while the normal alkane and isoalkane increased from deep to surface. Moreover, the ultraviolet derivative values of 280 nm and 210 nm decreased. These clearly indicate the direction of hydro-carbon vertical migration and show that the surface hydrocarbon anomalies have relation with deep reservoir. In a gas well in west Sichuan area, the hydrocarbon chromatogram of C1-C5 and the 3D fluorescence chromatogram of the near-surface sample are similar to that of the reservoir sample, showing the both having the same source.