Lithofacies characteristics and sedimentary models for He_1 member in Jin 58 well block of Dongsheng gas field

The sedimentary environment of He1 member in Jin 58 well block of Dongsheng gas field belongs to an alluvial fan-braided river sedimentary environment and the main sedimentary mode is the traction flow. There are nine types of lithofacies developed and the block stratified sandstone facies is the most common, followed by the gravel coarse sandstone facies. The sedimentary microfacies are mainly composed of mid-channel bar, braided channel, river-flood deposit and the vertical combination. In the north, the alluvial fan braided river is the main body, the medium-fine-conglomerate rocks are developed, and it mainly consists of the block bedding and groove cross-bedding. In the south, the braided river in alluvial plain is the main body, while medium sandstone and fine sandstone are developed, the thickness of the sand body is small, and it mainly consists of the groove cross-bedding and parallel bedding. The multilayer superimposed large lithologic traps form the main reservoir in box 1 section of Jin 58 well block, the favorable reservoirs are mainly distributed in midchannel bar and braided channel microfacies.