Oil & Gas Geology ›› 2019, Vol. 40 ›› Issue (2): 403-412.doi: 10.11743/ogg20190218

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Sedimentary microfacies and setting of the Upper Ordovician carbonates in the Yubei area,Tarim Basin

Cai Xiyao, Gao Xiaopeng, Li Huili, Zhao Yi   

  1. Petroleum Exploration and Production Research Institute, SINOPEC, Beijing 100083, China
  • Received:2018-08-05 Revised:2018-11-30 Online:2019-04-28 Published:2019-01-23

Abstract: We studied the microfacies types and sedimentary settings of carbonate rocks of the Upper Ordovician Qrebake and Lianglitage Formations from 12 wells of the Yubei area,by means of microfacies analysis.Eight kinds of carbonate microfacies have been identified based on the microscopic observation of grains,biological assemblies,matrix and structural characteristics.Based on how the microfacies types are associated to each other,combined with drilling and logging data,as well as seismic profile,palaeontological and geochemical analyses,we believed that the Upper Ordovician carbonate rocks are mainly developed in the sedimentary environments of open platform,platform margin and marginal-platform slope.The sedimentary facies in the Late Ordovician differ from the east to the west.The boundary is delineated along Well YB5-Well SH2-the south of Well PSB2,with marginal-platform slope-continental shelf facies in the east,and carbonate platform facies in the center and the west.In conclusion,the Upper Ordovician in the Yubei area has evolved from open platform,to platform margin,to marginal-platform slope,and then to continental shelf facies in vertical sequence,and the variation of sedimentary environments in the area is mainly controlled by regional tectonic movements.

Key words: microfacies, sedimentary setting, carbonate rock, Upper Ordovician, Yubei area, Tarim Basin

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