Reservoir Development Geological Study In Third Member Of Shahejie Formation In South-Banqiao Sag Of Huanghua Depression,Bohai Bay Basin

The South-Banqiao sag area of Dagang oilfield is located in Huanghua Depression,Bohai Bay Basin.The third member of Shahejie formation exists continuous layer and widely distributed.Because of relative more faults,the geological structure is complex.The oil-layer is thin,distribute dispersively,so the fine reservoir geological research is necessary.This paper taking structural geology,stratigraphic geology,sedimentology,logging geology,reservoir geology theories as the foundation,combined with logging,seismic,core and oil testing data,giving an integrated research for reservoirs in the third member of Shahejie formation of South-Banqiao sag area.According to the cycles characteristics with sequence stratigraphic theories,the studied area of the third member of Shahejie formation is divided into three reservoir sets,in which Es₃² can divided into 3 groups,Es₃³ can divided into 5 groups.On the basis of stratigraphic correlation,combined with seismic interpretation,this paper analysis the structural and the development of faults in the studied area.this paper also analysis the traps characteristics.Considering with regional sedimentary background,we researched on sedimentary facies marks,sedimentary facies characteristics.It is suggested that the target formations are mainly from fan delta sand bodies,which consist of underwater distributary channel,distributary bay,mouth bar and shallow lake.According to the reservoir inversion result,reveals the sedimentary and sand body distribution laws.The lithology of reservoir in study area is mainly arcose sandstone,granularity for fine sand grade,compositional maturity and structural maturity are low.The reservoirs are dominated by moderate-low porosity and low permeability sand,and pores connectedwith fine throat,microscopic heterogeneity is strong.The distribution of hydrocarbon is mainly controlled by faults,sedimentary,reservoir,according to drilled well geological data,seismic interpretation data,well logging interpretation data and oil testing data,we analysis the studied area developed fault block reservoirs,sand lens reservoirs,and updip pinch-out sandstone reservoir.The target layers have no constant oil-water contact with complex relations of oil and water.The production is related to multi-factors,such as reservoir thickness,sedimentary,porosity,permeability,oil saturation.Oil testing result indicate that wells with oil production greater than 10 t/d are from Es₃²reservoir,which is the major hydrocarbon reservoir in the third member of Shahejie Formation.The underwater distributary channel and the mouth bar sand bodies in the northwest are the favorable targets of hydrocarbon exploration in the future.