塔中志留系沥青砂岩的地质特征及研究进展

Geologic Feature and Study Progress of Silurian Asphaltic Sandstone in Tazhong Area, Tarim Basin

塔里木盆地塔中地区广泛分布着志留系沥青砂岩,主要分布在古隆起和早古生代生油盆地的上倾方向,表明本区规模巨大的志留系沥青砂岩可能为古油藏露头带。沥青砂岩的分布主要受油源区、古隆起、沉积体系以及储集层物性的综合控制,沥青的微观特征也反映了志留系油气多期注入和破坏的历史。油质沥青与胶质-沥青质的含量呈彼此消长关系,沥青含量高的部位可动油相对较少。由于存在不同期次的沥青,沥青反射率的数据比较离散。总体而言,沥青反射率均较低,为0.15%～0.50%.通过烃源岩及构造演化史研究认为,塔中志留系沥青砂岩的油源主要为中-下寒武统。

The Silurian asphalt sandstone is widespread in Tazhong area of Tarim basin and mainly found in the upper slope of paleouplift and oil-generating basin of Lower Paleozoic, which shows that the widespread asphalt sandstone could be the outcrop of paleo-oil pools in this area. The distribution of asphalt sandstone is mostly controlled by oil source, paleo-uplift, sedimentary system and petrophysical property. Microscopically, the asphalt characteristic also reflects the multi-stage filling and destructive accumulation history of Silurian hydrocarbons, with ebb and flow of oily bitumen content and colloid-asphhenes content, The strata with high asphhenes content appear relatively low volume of movable oil, and the bituminous reflectance is low and scattered, averaging 0.15%-0.50%. It is concluded that the source supply of Silurian asphalt sandstone is mainly from Middle and Lower Cambrian.