古城地区碳酸盐岩沉积特征及其主控因素

Carbonate Rock Sedimentation and Its Main-Controlling Factors in Gucheng

通过岩心精细描述、薄片鉴定、测井和地震特征及古地貌等分析,认为塔里木盆地古城地区寒武—中晚奥陶世主要处在台地—台地边缘—台缘斜坡相带,发育台内滩、台地边缘滩(礁滩复合体)、滩间海、台缘斜坡等微相类型。中下奥陶统鹰山组三段台缘滩和中上寒武统发育的纵向叠置的台缘丘滩体是有利的沉积相带,也是下一步勘探的重点。古地貌特征及其演化控制着沉积相带及礁滩体的分布,台缘坡折带决定了台缘带的分布位置,古地貌高隆区控制着台缘滩的发育。塔东地区沉积相演化主要受海平面升降控制,表现为台地类型的变化和台地边缘相带的迁移。探讨古城地区碳酸盐岩台地沉积微相特征及主控因素,圈定有利沉积相带,对于该区下步油气勘探具有重要的指导意义。

Fine core description,thin-section analysis,well logging,seismic interpretation,palaeogeomorphology and other analyses consider that the Cambrian-Middle-Late Ordovician strata in Gucheng of Tarim Basin mainly lie in platform-platform margin-epiplatform slope facies,which include intraplatform shoal,platform margin beach( reef-beach complex),beach interact sea,epiplatform slope and other sedimentary microfacies. The platform margin beaches in the Lower Ordovician Yingshan-3 and the Middle-Upper Cambrian overlapped platform margin bioherms-shoal flats in the longitudinal direction are considered as favorable sedimentary facies and favorable areas in the subsequent exploration. The distributions of sedimentary facies and reef-beaches are dependents on palaeogeomorphology and its evolution,the distribution of platform margin is dependent on platform slope and the development of platform margin beach is dependent on the high uplift of palaeogeomorphology. The sedimentary facies evolution in the east of Tarim Basin is controlled by sea level,which is characterized by the change of platform types and the migration of platform margin facies. The analysis of carbonate platform sedimentary microfacies properties and main-controlling factors and identification of favorable sedimentary facies in Gucheng could provide a significant guidance for the further hydrocarbon exploration in this area.