Abstract:

Beachbar sandstone is thin and interbedded sediment that was widely developed in the highenergy shallowshore lake environment. No enough attention has been paid to it and the exploration degree is very low. Focused on the research difficulties of beachbar sandstone causes and oil accumulation in the upper of Es4 of Dongying Sag, this paper studies sedimentary characteristics, oilforming factors and enriched regular pattern of beachbar sandstone. It was suggested that the beachbar sandstone deposition was controlled by palaeogeomorphology, palaeocurrent and palaeobase level (three palaeocontrolling sandstone mechanism), while oil accumulation was controlled by faults and fractures, effective reservoir and overpressure of source rocks (three factorcontrolling oil accumulation mechanism). Longterm palaeobase level rising and shortterm frequent palaeobase level concussion formed the widespread beachbar sandstone deposition. The “pressuresuck filling” caused by overpressure of source rocks and the water consumption and pressure reduction during the diagenetic process resulted in the widely bearing oils in the beachbar sandstones. 

Key words: continental faulted basins, beachbar sandstone, three sedimentary controlling factors, three oil forming controlling factors, Dongying Sag