酒泉中新生代断坳叠合盆地及控油作用

Mesozoic and Cenozoic Fault Superposition Basin in Jiuquan and Its Oil-Controlling Significance

基于盆地大地构造背景、盆地几何形态、沉积构造特征、古地温及火山岩等沉积盆地鉴别标志,认为酒泉盆地为中新生代断坳叠合盆地,中生代早白垩世属伸展断陷盆地,新生代为陆内挤压坳陷盆地和陆内前陆盆地。盆地叠合类型为陆内坳陷盆地和陆内前陆盆地与断陷盆地叠合,叠合方式总体为正交式叠合,其中陆内坳陷盆地与断陷盆地叠合方式可以划分为披盖叠合型、局部叠合型、未叠合型3类,按照断陷盆地与陆内前陆盆地构造单元叠合位置,将陆内前陆盆地与断陷盆地叠合方式划分为前陆冲断带与次级凹陷的叠合、前陆坳陷与次级凹陷的叠合、前陆斜坡与次级凹陷的叠合、隆后坳陷与次级凹陷的叠合4个亚类。中新生代盆地叠合控制了酒泉盆地油气成藏,早白垩世断陷盆地控制了烃源岩分布,决定了不同次级凹陷(含油气系统的)范围和优劣,中新生代盆地叠合不仅加速了烃源岩成熟,为油气运移提供了强大动力,而且对构造圈闭、油气运移通道的形成、储层物性的改善(裂缝的发育)起关键的作用。由于不同的次级凹陷叠合方式和叠合强度的差异,导致了油气运移、聚集成藏差异,油藏特征和油气富集程度不同。

Based on identification markers of sedimentary basins such as tectonic settings and geometry of the basins,sedimentary structures,paleogeotemperature and volcanic rocks,it is concluded that Jiuquan basin is a Mesozoic and Cenozoic fault superposition basin,which was an extensional fault basin during Early Cretaceous and an intracontinental compressional fault basin and intercontinental foreland basin during Cenozoic.The basin of this kind is characterized by orthogonal superposition of between intracontinental fault basin or foreland basin and fault basin.Superposition modes of intracontinental fault superposition basins can be classified into drape,local and non-superposed.Based on the superposed structure location of the Cretaceous fault basin and intracontinental foreland basin,the superposition can be divided into four types： the superposition of the Cretaceous secondary sag with Cenozoic foreland thrust belt,the Cretaceous secondary sag with Cenozoic foreland depression,the Cretaceous secondary sag with Cenozoic foreland slope and the Cretaceous secondary sag with Cenozoic depression after foreland uplift.During the Mesozoic and Cenozoic,superposition basins controlled oil and gas accumulation.Early Cretaceous fault basin controlled the distribution of hydrocarbon source rock,and scale and quality of various oil-and gas-bearing depressions.During Middle Cenozoic,basin superposition not only promoted source rock mature,provided strong forces for oil and gas migration,but also played a vital role in formation of structure traps and oil-gas migration and development of reservoirs fissures.It is the differences of superposition modes and various secondary depression intensities that jointly resulted in the differences of oil and gas migration and accumulation,reservoir characteristics and enrichment degree.