摘要
伊和乌苏凹陷是二连盆地西南缘勘探程度较低的凹陷之一,凹陷洼槽区钻探的Y2井在1619~2342 m钻遇大套变质岩。为搞清伊和乌苏凹陷的变质基底成因以及油气勘探潜力,对Y2井变质岩岩石学特征、地球化学特征、锆石U-Pb年代学特征以及伊和乌苏凹陷结构进行系统分析,研究结果表明:(1)Y2井变质岩岩性为白云母石英片岩、方解石英岩,变质程度低-中等,母岩为粉砂质泥岩或页岩。(2)变质岩表现为富Al_(2)O_(3)、K_(2)O特征,w(Cr)/w(Zr)值为0.309,w(Sr)/w(Ba)值为0.177,Sr表现出明显负异常,稀土元素质量分数在(La/Yb)_(N)与ΣY交汇图版上落在沉积岩或钙质泥质岩区。(3)变质岩的锆石U-Pb测年年龄可划分为3组(250.0±10.0 Ma、402.1±2.2 Ma、大于1064 Ma),第一组变质成因的锆石年龄对应的地层时代为晚二叠世,代表地层为晚二叠统或更老地层。(4)相对于邻区凹陷,伊和乌苏凹陷沉积缺失侏罗系、阿尔善组一段-三段及部分阿尔善组四段,目的层厚度小,中生界埋深浅,凹陷发育时期晚。伊和乌苏凹陷石油地质条件较差。
Yihe Wusu sag is one of the sags with low exploration degree in the southwest margin of Erlian Basin.A large set of metamorphic rocks was encountered in the range of 1619~2342 m in drilling process of well Yi2 in the trough area of Yihe Wusu sag.In order to understand the genesis of metamorphic basement and the exploration potential of oil and gas in Yihe Wusu sag,this paper systematically analyzes the petrological and geochemical characteristics and zircon U-Pb geochronology of metamorphic rocks in well Yi2 and the structure of Yihe Wusu sag.The results show that:(1)The metamorphic rocks of well Yi2 are muscovite quartz schist and calcite quartzite with low to medium metamorphic degree,and silty mudstone or shale is their parent rock.(2)The metamorphic rocks are rich in Al_(2)O_(3) and K_(2)O,with Cr/Zr value of 0.309 and Sr/Ba value of 0.177.The content of Sr shows obvious negative anomaly,and the mass fraction of REE is in the sedimentary rock or calcareous shale rock region in the crossplot chart of(La/Yb)_(N) andΣY.(3)Zircon U-Pb dating of metamorphic rocks can be divided into three groups(250.0±10.0 Ma,402.1±2.2 Ma,>1064 Ma).The`zircon age of the first group of metamorphic origin rock corresponds to the stratigraphic age of Late Permian,indicating that the strata are Late Permian or older.(4)Compared with the adjacent sags,Yihe Wusu sag lacks Jurassic,1st-3rd member and partial 4th member of Alshan Formation,with small target layer thickness,shallow buried depth of Mesozoic,later sag development period.The petroleum geological conditions in Yihe Wusu sag are relatively poor.
作者
刘瑛
刘护创
王文慧
赵春晨
陈治军
LIU Ying;LIU Huchuang;WANG Wenhui;ZHAO Chunchen;CHEN Zhijun(Research Institute,Shaanxi Yanchang Petroleum (Group) Co.,Ltd.,Xi’ an,Shaanxi 710075,China;Civil Engineering College,Shaanxi Polytechnic Institute,Xianyang,Shaanxi 712000,China)
出处
《西安石油大学学报（自然科学版）》
CAS
北大核心
2022年第3期16-26,共11页
Journal of Xi’an Shiyou University（Natural Science Edition）
基金
陕西延长石油(集团)有限责任公司2019年科技攻关项目“延长石油集团2020年油气勘探开发部署研究”(ycsy2019ky-A-03)。
关键词
变质基底
地层年代
岩石学特征
地球化学特征
石油地质条件
伊和乌苏凹陷
metamorphic basement
chronostratigraphy
lithological feature
geochemical characteristics
petroleum geological conditions
Yihe Wusu sag
