Distribution Characteristics of the Chang 6 Sedimentary System( Triassic) in Huanxian Area, Ordos Basin

Key words: 
• source of sediment /
• seismic facies /
• sedimental system /
• Chang 6 interval of the Yanchang Formation /
• Huanxian region /
• Ordos basin

Abstract: Decrease of debris and nonresistance minerals and increase of stable minerals such as quartz and zircon from west to east in the Huanxian region show that sediments of the Chang 6 delta system in this area was from the western regions. Three kinds of seismic facies could be recognized in the Chang 6 beds: the middle or high amp litude value-subparallel-relatively continuous reflection, the foreset reflection and the middle or low amp litude value-parallel reflection, corresponding to the deltaic plain, the deltaic front and the prodelta clay(or interdistributary clay) , respectively. Distribution characteristics of seismic facies suggest that the Huanxian Chang 6 delta system could be divided into two branches in the Hudong region: one extends easternwards from Huanxian to Fanjiachuan, another goes to Hongde in NE direction and meetswith the Anbian delta in Gengwan-Luobuyuan region. The front parts of the eastern Huanxian delta of Well Huan 4-Huan 41 are the ideal places to explore the lens and pinchout eservoirs.