肯基亚克盐下油田二叠系层序地层及沉积特征

Sequence stratigraphy and sedimentary features of the Permian in pre-salt Kenjiyake oilfield,Kazakhstan

哈萨克斯坦肯基亚克盐下油田二叠系为发育在石炭系碳酸盐岩台地上的一套陆源碎屑沉积,上覆巨厚的盐丘。目前在该区并没有建立起统一的层序地层格架,沉积相类型和分布规律尚不清楚,储层厚度薄、砂体形态多变,为盐下二叠系油气藏的勘探开发带来了困难。为此,在层序地层学理论的指导下,综合利用岩心、测井、三维地震资料,以层序边界特征为划分依据,将盐下二叠系划分为SⅠ、SⅡ、SⅢ3个三级层序。在建立等时地层格架的基础上,对该区的沉积相进行了研究,根据岩心相、测井相和地震相,识别出辫状河三角洲前缘、滨浅海和三角洲前缘滑塌浊积体等沉积相类型,同时分析了其沉积相特征,搞清了各层序内部沉积砂体的平面展布规律,明确了辫状河三角洲前缘和三角洲前缘滑塌浊积体为有利的储集体。

The Permian in the pre-salt Kenjiyake oilfield,Kazakhstan,consists of terrigenous detrital rocks deposited on the Carboniferous platform and is overlain by a super-thick salt dome.No unified sequence stratigraphic framework has been established in the study area till now.The types and distribution of sedimentary facies are unclear.The reservoir sandstones are thin in thickness and variable in shape.All these factors are challenging the exploration and development of the pre-salt Permian oil and gas reservoirs.Under the guidance of sequence stratigraphy theories,core,logging and 3D seismic data are integrated to divide the Permian into three third-order sequences,namely SⅠ,SⅡ and SⅢ,according to the characteristics of sequence boundaries.Based on an isochronous stratigraphic framework,several types of sedimentary facies,including braided river delta front,littoral to neritic,delta front slump turbidite facies,are identified in the study area according to core,logging and seismic facies.In addition,the features of each facies are analyzed,and the areal distribution of sandbodies in each sequence is identified.It is believed that the braided river delta front and delta front slump tuibidite are favorable reservoirs.