新生代柴达木盆地构造演化与油气勘探领域

Cenozoic Tectonic Evolution and Oil/gas Exploration Field in Qaidam Basin

通过地震剖面的重新对比解释,对盆地构造格架、形成演化有了新的认识。认为第四纪与第三纪柴达木盆地为不同构造背景下发育的叠合盆地。第三纪柴达木盆地主要位于乌图美仁—大柴旦断裂带以西,第四纪盆地主要位于该断裂带以东,一里坪坳陷是两期盆地的主要叠合区域。第三纪盆地形成于早喜马拉雅运动,发展于中喜马拉雅运动,消亡于晚喜马拉雅运动,经历了由断陷到坳陷至反转隆升的过程。下第三系具有多个沉积沉降中心,中新统与上新统具有相对统一的坳陷中心,后期构造变形强烈,断裂、褶皱发育。而第四纪盆地形成于晚喜马拉雅运动,为走滑盆地,沉积中心在纵向上向东有所迁移,构造变形弱,多为同沉积构造,幅度较小。柴达木盆地独特的油气地质条件,决定了在油气勘探上必须采取非常规思路和方法,向斜部位、构造裂缝可能有大发现。

Through new correlation and interpretation of seismic profiles, the new idea has formed to understand the tectonic framework,formation and evolution of Qaidam Basin. It is thought that in Quaternary and Tertiary, Qaidam Basin is a superimposed basin developed underthe different tectonic backgrounds.During Tertiary, the basin is mainly located in the west of Wutumeiren-Dachaidan fault zone, and in Quaternary, itis mainly situated in the east of Wutumeiren-Dachaidan fault zone. Yiliping sag belongs to the main superimposed area generated by the basinduring the two periods Quaternary and Tertiary. Tertiary Qaidam Basin formed during early Himalayan movement, grew during middle Himalayanmovement, and died out in later Himalayan movement, underwent a whole process from fault-depression, depression and reversal to uplift. Inlower Tertiary, there are several depositional centers in Qaidam Basin, in Miocene and Pliocene period, the basin has a relatively uniformdepositional centre, in the later period, tectonic deformation was much more strong, and faults and folds developed. The Quaternary basin,formed in later Himalayan movement, is a strike-slip basin, the depositional centre moved straight forwardly toward the east, tectonic deformationwas weak, these structures are syn-depositional ones, the amplitude is relatively small. Qaidam Basin has the unique petroleum geologic conditions,so we must adopt the unconventional idea and method to explore for oil and gas in this basin, the big discovery could be discovered in thesyncline position and structure fractures.