鄂尔多斯盆地南部旬宜地区及周缘马家沟组层序地层研究

Study of sequence stratigraphy of Majiagou Formation in Xunyi area and its periphery,South Ordos Basin

在充分汲取前人关于鄂尔多斯盆地层序地层研究精华的基础之上,主要依据旬宜地区及周缘11口探井录井资料及30多口钻井测井资料,识别出5个层序界面,将奥陶系马家沟组划分出5个平均时限为3.54 Ma的三级层序,即SQ1~SQ5,从层序界面性质来看,层序SQ1底部界面和层序SQ4顶部界面为Ⅰ型,其余层序界面全部为Ⅱ型。根据岩相组合、自然伽马曲线特征、构造运动、沉积演化等将SQ1划分为低位、海侵和高位三个体系域,SQ2、SQ3、SQ4、SQ5划分为海侵和高位两个体系域。为鄂尔多斯盆地南部尤其是旬宜地区马家沟组的油气勘探提供理论依据。

According to the previous research result of sequence stratigraphy in Ordos Basin,the paper has identified for five sequence boundaries on the basis of logging data of 11 exploration wells and logging data of more than 30 drilling wells in the Ordos Basin.The Ordovician Majiagou Formation are divided into five third-order sequences with an average time limit of 3.54 Ma,namely SQ1-SQ5.For the nature of the sequence interface,the bottom interface of sequence SQ1 and the top interface of sequence SQ4 are type Ⅰ,and the rest sequence interfaces are all type Ⅱ.According to lithoface,natural gamma curve characteristics,tectonic movement,sedimentary evolution,etc.,SQ1 is divided into three system tracts,low,transgressive,and high.SQ2,SQ3,SQ4,and SQ5 are divided into two system tracts,transgressive and high.It provides a theoretical basis for oil and gas exploration of Majiagou Formation in the southern Ordos Basin,especially in the Xunyi area.