Abstract:

According to core and logging data，this paper examines the origins and assemblage types of sandbodies in the Permian Shanxi Formation in Daniudi gasfield，the Ordos Basin.We believe that the genetic types of sand-bodies in the Shanxi Formation include underwater distributary channel sands，mouth bar sands，distal bar sands and sheet-like sands.The Shanxi Formation consists of4types of braided river delta front sandbody assemblages，including superimposed and scoured underwater distributary channel sands，overlappedmouth bars，underwater distributary water-mouth bar sands and distal bar sands sheet-like sands.Ways and volume of sediment input and change of accommodation are the key factors that control the temperal and spatial distribution patterns of sandbody assemblages of different genetic types during the deposition of the ShanxiFormation in Daniudi gasfield.Based on these results，we set up two geneticmodelss of sandbodies for the study area，one being prograding accommodation decreasingmodel and the other being retrograding accommodation enlargingmodel.It is proposed thatunderwater distributary channel sands and distributarymouth bar sands are the potential exploration targets in the ShanxiFormation.

Key words: delta front, sand assemblage type, sand geneticmodel, ShanxiFormation, Daniudi gasfield, Ordos Basin