塔中地区中及上奥陶统沉积相

中及上奥陶统是塔中地区主要的油气勘探目的层系之一。在综合地层划分对比的基础上，分析了塔中地区不同沉积相的分布规律。礁滩沉积和斜坡沉积构成了台地边缘相的主体。碳酸盐台地上不同期次发育的边缘相是重要的油气储集体。它们主要分布于塔中I号断裂构造带和TZ10井构造带和塔中南缘断裂构造带上，沉积厚度相对较大。因此，可以得出这样的结论，这种分布状况代表了塔中地区构造对沉积相带的控制作用。通过大量二维及三维地震资料解释分析，发现在塔中广泛分布的丘状隆起地震相、楔状前积反射地震相和杂乱反射地震相相同样多沿主要构造线延伸，内部反射杂乱，成乱岗状反射。把已经认识的沉积相类型和这些地震相的分布特征相比较，可以确定这种地震相就是碳酸盐台地边缘相沉积体。这样，就有可能利用丰富的地震资料，预测有利油气富集的储集体的展布规律。

SEDIMENTARY FACIES OF THE MIDDLE AND UPPER ORDOVICIAN IN THE CENTRAL TARIM AREA

The Middle and Upper Ordovician is one of the main target zones of oil and gas in the Central Tarim area.On the basis of synthetic stratigraphic subdivision and subcorrelation, this paper has analysed the distribution of different sedimentary facies.The platform marginal facies is mainly composed of reef, shoal and slope deposits,and these facies were developed in different evolution stages of the carbonate platform and have constituted important oil and gas resevoirs in the research area.These facies have a relatively larger thickness and are mainly distributed in the No.1 faulting zone,the TZ10 structure zone and southern edge faulting zone of the Tazhong area.It is concluded that in the Tazhong area, the synsedimentary structures in the Middle and Upper Ordovician had an important influence on the formation of these platform marginal facies.Through interpretation of a large amount of 2 D and 3 D seismic data, we have found that three widely developed seismic facies,including mound like facies,sphenoid foreset facies and desultory reflection facies,are also mainly distributed along the major structural zones.Compared with those well identified sedimentary facies,these seismic facies are regarded to be the platform marginal facies.In this way,the accurate positions of the marginal facies can be figured out through processing of a large amount of seismic data.