酒泉盆地群热演化史恢复及其对比研究

酒泉盆地群是由两期不同性质、不同世代盆地叠加而成的 .晚侏罗纪-早白垩世为拉张断陷盆地 ,第三纪以来为挤压坳陷盆地 .酒泉盆地群现今地温梯度及大地热流值都较低 ,地温梯度主要在 2 51- 3 0 0℃ /1 0 0m之间 ,大地热流值在 50- 57mW /m2 之间 .酒泉盆地群中生代晚期为拉张断陷 ,古地温梯度高 ,可达 3 75- 4 50℃ /1 0 0m ,新生代以来地温梯度逐渐降低 ,而花海盆地、酒西盆地石北凹陷沉降幅度小 ,古地温高于今地温 .下白垩统烃源岩热演化程度受古地温控制 .主生烃期仅有一次 ,为早白垩世晚期 .酒西盆地青西凹陷、酒东盆地营尔凹陷在新生代以来大幅度沉降 ,下白垩统烃源岩热演化程度受现今地温控制 .主生烃期有两次 ,一次为早白垩世晚期 ,另一次为晚第三纪以来 ,且以晚第三纪以来为主 .不同盆地及同一盆地不同构造单元由于构造热演化史的不同 ,主生烃期及油气勘探前景明显不同 .

RECOVERY AND COMPARATIVE RESEARCH OF THERMAL HISTORY ON JIUQUAN BASIN GROUP

Jiuquan basin group is formed by the stacking of two stage basins with different property and different generation. It was rift basin in Late Jurassic Early Creaceous and squeezed sag basin since Cenozoic. The present geothermal gradient between 2.5℃/100m and 3.00℃/100m and heat flow between 50mW/m 2 and 57mW/m 2 is low in Jiuquan basin group. Jiuquan basin group is rift basin and its palaeothermal gradient is higher in late Mesozoic, which reached 3.75-4.50℃/100m. The thermal gradient has decreased since Cenozoic. Huahai basin and Shibei depression of Jiuxi basin have subsided at a small increase since Cenozoic, the palaeotemperature of lower Cretaceous source rock is higher than present, the maturity of lower Cretaceous sources rock is controlled by palaeotemperature. There is only one stage of main oil generation, Early Cretaceous. Qingxi depression of Jiuxi basin and Yinger depression of Jiudong basin have subsided at a big increase since Cenozoic, the maturity of lower Cretaceous source rock is mainly controlled by present temperature. There are two stages of main oil generation, late of Early Cretaceous and Late Tertiary, main stage of oil generation is Late Tertiary. The difference of tectonic thermal history in different basin and different units of a basin result in difference of stage of main oil generation and difference of oil gas exploration prospect.