中东地区阿普特阶Shuaiba组碳酸盐岩沉积体系特征及模式探究

Geological characteristics of sedimentary system and model of Shuaiba Formation at Aptian Stage,Middle East

中东地区主力产油层系Shuaiba组的勘探及研究逐渐以地层岩性圈闭为主,笔者通过总结Bab盆地阿普特阶Shuaiba组沉积相类型,多油田地层格架及空间展布特征的对比,为系统恢复Shuaiba组沉积演化过程及模式提供地质依据。研究表明,阿普特阶Shuaiba组共发育开阔台地、台地边缘、台缘斜坡及盆地相4种沉积相单元和6种亚相类型,各相带单元受控于四个三级层序且沿Bab盆地周缘呈带状展布。开阔台地一侧,主要沉积了第二个三级层序对应的Lower Shuaiba地层;台地边缘往Bab台内盆地区域,则以第三和第四个三级层序对应的Upper Shuaiba地层为主。Shuaiba组生物礁、滩建造集中发育在第二个三级层序的高位域阶段,滩间海、缓坡及盆地相受控于海进和低位体系域。阿普特阶Shuaiba台地边缘生物建隆、台内浅滩在空间上相互叠置并成带展布,符合弱镶边型缓坡台地沉积模式,该类型台地具备深水陆棚性质的非常宽缓的斜坡,且缓坡往盆地一侧发育一个镶边台地边缘。

Shuaiba Formation is one of the main productive zones in the Middle East,and its exploration and research issues are mainly related to the stratigraphic-lithologic trap at present.On the basis of limited cores,well logging and geophysical data,the sedimentary facies at Aptian Stage were summarized.By analyzing the stratigraphic framework and comparing the spatial distribution features of each sedimentary unit,we restored the evolution process of the sedimentary units and established the carbonate sedimentary model.It is concluded that,there are four types of sedimentary facies and six sub-facies exist in the Shuaiba Formation,including open platform,platform margin,slope and basin facies.Sedimentary facies are controlled by four third-order sequences and distributed along the periphery of the Bab Basin.The sediments of Lower Shuaiba strata formed in the open platform and related to the second third-order sequence,while the Upper Shuaiba strata which corresponds to the third and fourth third-order sequences are dominated from the platform edge to the Bab Basin.The Shuaiba reef and shoal are concentrated at high stand system tract of second third-order sequence,and the interbank sea,slope and the basin facies are related to the transgressive or low system tracts.The identification and comparison of sedimentary facies show that,weak rimmed carbonate ramp-platform developed during the Aptian.The weak rimmed carbonate rampplatform has very gentle slope and gentle slope with a weak reef construction.The platform marginal reef and shoal superimposed each other and distributed as a belt in region.