酒泉中新生代断坳叠合盆地及控油作用

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。

Superposition Characteristics of Jiuquan Mesozoic and Cenozoic Basin and its Control on Oil and Gas

By the research on the tectonic setting, geometry, Sedimentary, basin structure, Paleo-geothermal field and volcanic rock of Jiuquan Mesozoic and Cenozoic Basin, this paper concludes that Jiuquan Mesozoic and Cenozoic Basin is a superposed basin. In Cretaceous, the basin is controlled by NE-trending structures in extensional dynamic setting. Paleogene depression basin or Neogene intracontinental foreland basin formed in compressional dynamic setting in Cenozoic and controlled by NWW-trending structures. The basins superposed in overpass ways. There are three types of Cretaceous faulted basin superposed Paleogene depression basin such as drape superposition, local superposition and non- superposition. According to the superposed structure location of the Cretaceous faulted basin and intracontinental foreland basin, the superposed type 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. The oil and gas accumulation is controlled by superposition of Mesozoic and Cenozoic Basins. The hydrocarbon source rock distribution is controlled by early- Cretaceous faulted basin and in different secondary sag, the source rock quality is different. The basin superposition not only promote source rock mature but also control the formation of structure traps, oil-gas migration channel and fractures of rock. The oil and gas accumulation enrichment is different because of the difference of superposed mode and strength in different secondary sags.