塔中上奥陶统台缘带高频层序地层特征与储层纵向分布

THE CHARACTERISTICS AND ITS AFFECTS TO RESERVOIRS OF HIGH-FREQUENCY SEQUENCE OF UPPER ORDOVICIAN PLATFORM MARGIN IN TAZHONG AREA

利用钍／钾比分析技术，结合岩心与常规测井资料，可识别并划分对比塔中上奥陶统台缘带碳酸盐岩高频层序．分析表明，奥陶系碳酸盐岩呈明显米级旋回变化，在60m井段识别出20个短周期旋回、4个长周期旋回，单个旋回厚度2～4m．高频层序与礁滩体沉积旋回具很好对应关系，可用于沉积旋回精细划分与对比．礁滩体储层呈多旋回米级变化，长周期旋回顶部与优质储层对应非常好．高频层序与储层对比分析表明，优质储层主要发育在海平面向上变浅的米级旋回中，井间对比分析也呈相同特点．钻井分析表明，在3个海平面变浅的长周期旋回顶面均是优质储层发育段，3期长周期旋回的海平面下降期暴露面形成3套优质储层发育段．结果表明，高频层序与优质储层发育关系密切，准同生期溶蚀作用主要发育在相对海平面下降的米级旋回暴露期礁滩体中．

Based on the cores and logging date, high-frequency sequence can be identified and correlation by the Th/K analysis technology of gamma ray logging in the platform margin of upper Ordovician carbonate in Tazhong uplift, Tarim basin. It is indicated that there are obvious meter-scale cyclic in the upper Ordovician carbonat. It can be identified 4 long cycles and 20 short cyles in 60 meters section of a well, and the short cycle thickness is up to 2-4 meters. High-frequency sequence has not only the good correlation with reef-bank complex sedimentary cycles, but also can be used as a tool to sedimentary cycle division and correlation. Long cycle sequence has a good correlation with the meter-scale cycle reservoir. Reef-bank reservoirs has the meter-scale cycle and correspond to the top of long cycle sequence by the analysis of well date. The good reef-bank reservoirs are distributed in the meter-scale cycles with generally upward shallowing succession by the high-frequency sequence and reservoir correlation. It is showed that there are 3 reservoir section developed in the top of the 3 long cycles sequence with upward shallowing succession. Penecontemporaneous meteoric water dissolution is the main controlling factor for reef-bank matrix porosity development, the favorable reservoirs were developed in the exposure stage of relative sea level descending with meter-scale cycle.