Abstract: The northern area of Qaidam Basin was considered as a compressive basin in the Jurassic and Cretaceous times.In reality,it had involved into a flexural basin as a result of weak compression since the Early-Mid Jurassic.This inference is based upon the restoration study of several main structural cross sections,regional geological data,and analysis of petroliferous circumstances. The Jurassic source rocks still possessed an oil-bearing potential in the Cenozoic time,because they did not reach the threshold of hydrocarbon generation during the Mesozoic burial history.Two periods of strong contractile deformation occurred in the Late Eocene and since the Pliocene respectively were recognized.The deformations had obvious influence on the formation of oil-gas pools.Correspondingly,there existed two types of pools,e.g.primary and secondary pools.The primary pools were developed in traps formed during the first-epoch and previous compression deformation, while the secondary pools only occurred during the second epoch in the shallow-level and fault-bounded fold traps and would be generated only in the regions strongly modified by intensive faults that clearly penetrated into the Pliocene and underlying strata.

Key words: Qaidam Basin, Cenozoic era, Miocene era, structural evolution, structural section restoration, hydrocarbon accumulation

摘要： 对柴北缘主干剖面构造变形演化的平衡剖面进行了恢复研究,对其区域地质资料和石油地质条件的分析结果表明,柴北缘侏罗-白垩纪为挤压型盆地,其中早-中侏罗世可能属于弱挤压挠曲盆地.侏罗系烃源岩在中生代构造演化过程中,埋深未达生油门限,故在新生代仍具有良好的生烃潜力.柴北缘新生代具有晚始新统下干柴沟组上段(E32)沉积期间和上新统狮子沟组(N23)沉积以来两个与油气成藏密切相关的强烈构造挤压时期,相应地形成原生和次生两种类型的油气藏.原生油气藏主要聚集在晚始新统下干柴沟组上段(E32)沉积期间第一次强烈变形时期及其之前形成的圈闭之中;次生油气藏形成于第二次强烈构造挤压时期,并只可能形成于发生强烈构造挤压作用破坏、并有断层下切到上始新统下干柴沟组下段(E32)及其以下地层的区域浅层圈闭或在断层相关褶皱中形成.

关键词: 柴达木盆地, 中生代, 新生代, 构造演化, 构造剖面恢复, 油气成藏