大巴山南侧城口油苗点油源分析

ANALYSIS OF THE SEEPAGE OIL AND OIL SOURCE IN CHENGKOU AREA OF THE SOUTHERN MARGIN OF DABASHAN

通过对出露于大巴山前缘一系列逆冲断层带上的液态油苗与秦岭南缘及邻区烃源岩的地球化学对比研究表明:油苗点碳同位素与下古生界烃源岩抽提物碳同位素较为接近,与二叠系烃源岩抽提物差异较大,反映油苗点的油与下古生界亲缘关系较好。但质谱分析表明,油苗点的生物标志化合物参数却与二叠系烃源岩更为相似。结合研究区的构造—沉积演化史、烃源岩的生烃演化史研究认为:油苗点油源来自于二叠系烃源岩,在运移充注过程中混入了下古生界烃源岩的有机地球化学信息。

The oil seepages were occurred along a series of thrust faults in the front of Dabashan. Based on comparative analysis of the source rocks in the southern margin of Qinling mountain and its surroundings and the seepage oil in Chengkou area, it showes that carbon isotope of the seepage oil is close to that of the extract of the Lower Paleozoic source rocks, but different with that of the extract of the Permian source rocks. The results show intimate relationship between the seepage oil and the Lower Pa leozoic source rocks. However, the biomarker parameters by GS-MS indicate that the seepage oil is more similar to the Permian source rocks. According to analysis of tectono-depositional history and hy- drocarbon generation history of the source rocks, the seepage oil came from the Permian source rocks. During hydrocarbon migration and entrapment, some organic geochemical information of the Lower Paleozoic source rocks was mixed.