塔河油田奥陶系油气成藏期次及年代学

Timing and chronology of hydrocarbon charging in the Ordovician of Tahe oilfield,Tarim Basin,NW China

多旋回叠合盆地油气成藏期次和成藏时期研究对油气运聚与圈闭时空匹配关系具有十分重要的意义。文章首先综合运用原油/油包裹体分子地球化学、单个流体包裹体荧光特性和显微测温等油气成藏期次划分方法,获得了塔河油田奥陶系发生了3期成藏的认识;接着,运用流体包裹体间接定年及Re-Os和K-Ar直接定年方法,构筑了其奥陶系油气成藏年代学格架。结果表明,塔河油田第一期成藏发生在加里东中-晚期（463.2~414.9 Ma）,第二期成藏发生在海西晚期（312.9~268.8 Ma）,第三期成藏发生在喜马拉雅期（22~4.8 Ma）。其中,塔河主体发生了3期成藏,而塔河外围仅发生了第一期和第2期两期成藏。深入剖析阿克库勒凸起受差异构造演化控制的成藏期次和成藏时期在空间上表现出的非均质性,对塔里木盆地下古生界其它构造带的勘探同样具有借鉴意义。

It is of great significance for study of the temporal-spatial coupling of hydrocarbon migration and accumulation with trap formation to investigate the timing and chronology of hydrocarbon charging in multi-stages superimposed basins.This study,firstly,employed the analytic methods of crude oil and oil inclusion molecular geochemistry,single fluid inclusion microspectrofluorimetric and thermal maturity assessment,and microthermistry to determine the timing of hydrocarbon charging in the Ordovician strata of Tahe oilfield. The results show that the hydrocarbons in the Ordovician were charged in three periods. Secondly,the indirect dating method of aqueous inclusion and the direct dating method of stable radioactive isotope of Re-Os and K-Ar were used to establish the chronological sequence： the first charging event took place during the Middle to Late Caledonian（ 463. 2- 414. 9 Ma）,the second charging event happened during the Late Hercynian（ 312. 9- 268. 8 Ma）,and the third charging event occurred during the Himalaya（ 22- 4. 8 Ma）. All the three events occurred in the main Tahe oilfield,but only the first and third events developed in the peripheral areas of Tahe oilfield,such as Aiding,Tuoputai and South Tahe areas. Obviously,a deep understanding of the heterogeneity of hydrocarbon charging events and chronology in Tahe oilfield,which were controlled by differential structure evolution,will be helpful for hydrocarbon exploration in the Ordovician of other structural belts of Tarim Basin.