In oil field of China, fluvial and delta facies reservoir are main depositional facies type, and their geological reserv中国油田河流相与三角洲相储层的地质储量占碎屑岩相总储量的近80％，是主要的沉积相类型。
This formation is dominated by a set of sandstone-mudstone dark clastic rock series which belongs to marginal marine dep该组主要为一套砂岩－泥岩的暗色碎屑岩系，属冈瓦纳石炭－二叠纪冰川末期的边缘海沉积。