顺南地区中奥陶统一间房组沉积微相特征与展布规律研究

Research on Sedimentary Microfacies Features and Distribution Law of Middle Ordvician Yijianfang Formation in Shunnan Area

顺南地区位于塔中隆起北部围斜区,其中奥陶统一间房组的存在已被证实,但一直以来并未对其沉积特征、沉积微相类型、组合及展布规律进行研究。通过对顺南地区6口已钻井的测井、录井资料分析以及岩性观察,详细阐述了顺南地区一间房组的沉积特征,将其层序格架划分至4个四级层序并在研究区内建立了一间房组高精度层序格架。最后,根据镜下薄片及岩心观察,将顺南地区一间房组沉积微相分为7种类型,3种微相组合。3种微相组合横向上分布局限,反映东部地区水体能量较西部略高;纵向上呈叠置发育,高位域以能量较低的滩间海为主,表现为对地貌的填平补齐,海侵域呈能量略高的滩-丘组合,为典型的海侵追长特征。

Although the existence of Middle Ordovician Yijianfang formation strata has been confirmed in Shunnan area,the north periclinal area of Tazhong uplift,the study on its sedimentary characteristics,sedimentary microfacies types,assemblages and distribution law has not been conducted.According to the analysis of logging data,mud logging data,and observation of lithology of 6 drilled wells in Shunnan area,this paper first elaborated the sedimentary characteristics of Yijianfang formation of Shunnan area and then divided the Yijianfang formation strata with high accuracy sequence into 4 forth-order sequences.Finally,it divided the sedimentary microfacies into seven typeswith three microfacies assemblages based on the observations and analysis of thin sections and core.Horizontally,the distribution of the three miacrofacies assemblages is limited,reflecting the higher water body energy in the east than that in the west.Vertically,the development of the three miacrofacies assemblages is superposed,with mainly low energy interbank sea in the highstand system tract（HST）,filling and leveling up the landform,and high energy interplatform beach-mound combination in the transgressive system tract（TST）,being typical of the transgressive feature.