塔里木盆地奥陶系碳酸盐岩颗粒滩沉积组合及展布特征

本文综合露头、钻/测井、地震以及薄片等资料的研究，开展了塔里木盆地奥陶系碳酸盐岩颗粒滩沉积特征的研究。本次研究首次厘定了颗粒滩的划分标准，总结了塔里木盆地奥陶系发育藻粒滩、内碎屑滩、鲕粒滩和生物碎屑滩四类颗粒滩；明确了四类颗粒滩的微观和宏观沉积特征:藻粒滩由藻粒、球粒和藻团块构成，与结晶云岩互层沉积；内碎屑的含量和形态揭示了内碎屑滩的部位和沉积区的能量，内碎屑滩自鹰山组开始大规模发育；鲕粒滩主体区其他颗粒类型不发育，鲕粒滩主要分布在塔中和玉北地区的台缘带；生物碎屑滩由生物骨架碎屑和生物颗粒构成，与生物礁复合共生，集中在台缘带及台缘内侧分布，一间房组开始大规模发育。颗粒滩发育段对应低GR值，主体部位GR曲线呈箱型、漏斗型或钟型，侧缘部位呈指状或尖峰状，台缘带颗粒滩向台内迁移呈退积反射特征。在此基础上，建立了塔里木盆地碳酸盐岩颗粒滩的四种沉积组合样式:藻礁滩互层式、厚层滩加积式、薄层滩退积式和生物礁滩复合式。其中，藻礁滩互层式和礁滩复合式颗粒滩分布受相带影响，具有局限性，易于形成有效油气藏，在塔中地区奥陶系已得到证实。厚层滩加积式和薄层滩退积式颗粒滩在鹰山组分布广泛，结合颗粒滩的沉积展布规律及储层成因分析，得出鹰山组颗粒滩储层具有区域优势分布特征。

Depositional Combination Characteristics and Distribution of Ordovician Carbonate Shoals in the Tarim Basin

Based on outcrops, drilling and logging well data, seismic data and thin sections, carbonate shoals depositional characteristics have been studied and the results have been summarized as follows: the classification criteria of the carbonate shoals have been established, and four types of  carbonate shoals (intraclastic shoal, oolitic shoal, bioclastic shoal and algae shoal) have developed in Ordovician; the sedimentary characteristics of the  micro and macro  Ordovician carbonate shoals have been integrated: the algal peloids, pellets and the algae clumps are the main components of algae shoals, and algae shoals are interbedded with algae crystalline dolomite; the content and shape of intraclastics shows the different parts of intraclastics shoals and their depositional environment energy, and intraclastics shoals have begun to develope in large-scale in the Yingshan Formation; oolitics shoals are mainly distributed in the platform marginal area of the Tazhong and Yubei area  with  a  few other grains developed in the main part of oolitics shoals; bioclastics shoals are composed of the reef fragments and bioclastics, and  are  developed with the reefs complex, and mainly distributed in the platform marginal area and the  margin area of inside adjacent platform.  The bioclastic shoals have developed in the Yijianfang Formation. The GR value are low corresponding to the shoals formation, and the GR mainly  shaped like box, funnel and  bell in  the shoals, while the finger and peak shapes are of the side part of the shoals. Furthermore, the shoals shows retrogradational migration from the marginal to the platform inside. According to the sedimentary characteristics, four carbonate stacking patterns have been established, including: algae-reef-shoal interbed, thick-layer cake aggradation shoal, and thin-layer cake retrogradation shoal, reef-shoal complex. Especially, algae-reef-shoal interbed and reef-shoal complex two stacking patterns distributions have been limited by the facies, but easily to form effective reservoirs, which have been proved in Ordovician of Tazhong area. The thick-layer cake aggradation shoals and thin-layer cake retrogradation shoals widely distributed in the Yingshan Formation. Therefore, combining the distribution characteristics and reservoir forming mechanism. It is conduded that  the carbonate shoal reservoirs of the Yingshan Formation have distributed with regional advantages.