Study on the sedimentary environment of Chang 8-6 oil-bearing formations of Yanchang Formation in Huanxian area,Ordos Basin

Based on the data of the well logging and drilling cores,the authors have observed 15 cores.They have analysed the petrology characters,sedimentary structures,biological fossils of the Chang 8-6 oil formations of Triassic Yanchang Formation in the Huanxian area.All the results suggest that in Chang 6 develops front-delta facies;in Chang 7 develops deep lake to half deep lake facies and turbidite fan and in Chang 8 develops prodelta facies.The front-delta facies is mainly distributed over the southwest of the study area and the turbidite fan is mainly distributed over the eastern of the study area.