塔中地区奥陶系碳酸盐岩不整合带的结构

Structure of Ordovician Carbonate Unconformity Zone in Tazhong Area

塔中地区中上奥陶统与下奥陶统之间发育碳酸盐岩不整合,不整合带是溶解作用发生的有利地带,可以作为烃类运移通道或油气聚集的场所。应用地质和地球物理方法对塔中地区奥陶系碳酸盐岩不整合进行了研究。塔中地区奥陶系碳酸盐岩不整合输导体在流体运动特点上不整合面上、下分属于两个不同的流体流动场,不整合面下,流动孔隙主要由孔洞缝孔隙体系构成,因此,流体的运动属于复杂介质条件下的流体运动,而不整合面上的层状渗透性体大多数情况下属于孔隙型介质,流体在其中的流动通常可以用达西定律加以描述。因此,不整合输导体中,流体从不整合面下向不整合面上运动,在流型上必然发生明显转换,这种转换对烃类的聚集是非常重要的。

The unconformity between the middle-upper and the lower Ordovician serials is well developed in Tazhong area. As the favorable place of dissolution, the unconformity zone has the function to serve as the pathway of the migration and accumulation of oil and gas because of the improvement of its physical property. The unconformity zone is of great significance in the petroleum prospecting. The structure of the Ordovician carbonate unconformity zone is studied by means of geological and geophysical method. There are two different fields of fluid flow above and under the Ordovician carbonate unconformity in terms of the characteristics of fluid flow in Tazhong area. The migration pathway under the unconformity is mainly composed of pores, caves, and fractures where the flow regularities are complicated. While the migration pathway above the unconformity mainly consists of pores where the fluid flow can be characterized by Darcy＇s law. Apparently, there will be a shift of the flow pattern when the fluid migrates upward to penetrate through the unconformity, and it is of great importance for the petroleum accumulation.