塔里木盆地下古生界油气晚期成烃成藏的地质依据

古老地层在特殊地质条件下可以晚期成烃成藏。研究表明:塔里木盆地自下古生界沉积以来,地温梯度整体递减的热史和多次地层抬升剥蚀降温,延缓了烃源岩热演化进程;差异埋藏热演化,使部分地区烃源岩的生烃潜力得以保持至喜山期;晚期的快速深埋升温使短期内大量生、排烃并高效运聚;为新构造期的断裂系统活化提供运移的通道;这些地质条件是下古生界油气可晚期成烃成藏的保证。塔中、轮南及环满加尔凹陷较深层是最具有晚期成烃成藏可能的区域。

The geological basis of late hydrocarbon generation and accumulation in the Lower Paleozoic of Tarim Basin.

On special geological conditions, the late hydrocarbon generation and accumulation can take place in older formations just as those in the Mesozoic and Cenozoic. The geothermal gradient is gradually decreased in Tarim Basin. The thermal evolution of the Lower Paleozoic was suspended frequently because of multiple uplift denudations of the overlying strata. Hence the organic matter evolution in the Lower Paleozoic was suspended. The differential burial evolution led to the differential thermal evolution in different structural belts. The hydrocarbon generation potential of source rock in some areas can be preserved up to Himalayan period. In Himalayan period, the source rock was buried deeply in short time so that the hydrocarbon was generated plentifully and accumulated efficiently. The activated fault systems in Neotectonic period made the hydrocarbon migration easy. These geological conditions caused the possibility of late hydrocarbon accumulation in Tarim Basin in the Lower Paleozoic. Tazhong, Lunnan and the deeper sites of Mangar Depression are the prospective areas.