Depositional system and its hydrocarbon characteristics of Shahejie group of Shengtuo region in Dongying depression

The early Tertiary Shahejie group is the most important reservoir in Shengtuo region,Dongying depression.Its depositional characteristics were researched by means of core observation,scanning electron microscope(SEM), core lab analysis data and seismic data.Glutenite suites of various genetic types developed in the northern abrupt slope,which take skirt-type distribution transversely along the northern Shengtuo region.High quality reservoir is mainly located in middle-fan plaiting channel sand body.Both fracture activity and hydrocarbon generation system seriously affect the prevailing reservoirs in studied area.Accordingly,lithologic hydrocarbon reservoir,structural hydrocarbon reservoir and stratigraphic hydrocarbon reservoir embed in downthrown side,fracture zone and upthrown side separately.According to oil-source correlation,oil found in the deep Es_4 and part in the upper layers is generated from Es_4 mature hydrocarbon.The low-mature heavy oil dominates in the Shengbei stratigraphic reservoir and upthrown side.Biomarkers reflect its upper-Es_4 origin.Oil in Es_3 is generated from downthrown side,while mixed source oil from Es_3 and Es_4 is observed in middle-shallow group.Hydrocarbon mainly migrates through reserve sandstone and faults.