Study On The Accumulation Model Of The First Member Of The Shahejie Formation In The Qingdong Area Of The Eastern Steep Slope Of The Western Liaohe Sag

This paper selects the Qingdong area of the east steep slope belt in the western sag of the Liaohe Oilfield as the research area,comprehensively uses petroleum geological research methods,combined with logging data,geochemical parameters,seismic data,and oil test data,etc.,through a detailed analysis of the reservoir to clarify The basic characteristics of different types of reservoirs,establish the distribution development model of multi-functional element control reservoirs,and clarify the main control factors of the distribution of different types of reservoirs.Provide a theoretical basis for the next fine exploration of the oil field.The sedimentary facies of the E₃s_1,Qingdong area are fan-delta sedimentary facies,which are close to hydrocarbon-generating sags and have sufficient supply of provenance,which is conducive to the accumulation of oil and gas.The results of the study indicate that the first member of the Shahejie Formation is mainly distributed in the middle and lower parts,the lithology is dominated by fine sandstone and siltstone,and a set of regional mudstone caps is developed on the top,with a thickness distribution of 15-180m;The formation pressure is normal pressure and partial overpressure,and the crude oil is light oil;the reservoir type is tectonic-lithologic reservoir,with nose-like structure in the east,and lithologic reservoir in the west;The crude oil and oil sand samples show source rocks derived from brackish water and brackish environment through crude oil group component analysis,saturated hydrocarbon chromatographic analysis and biomarker analysis,indicating that oil and gas are mainly derived from source rocks in the third member of Shahejie Formation.Analysis by crude oil physical tracer method shows that crude oil is mainly transported from west to east and from south to north through well-connected sand bodies;In the two-stage oil and gas accumulation,a small amount of oil and gas was accumulated before the Dongying deposition and was destroyed in the later period.A large amount of crude oil accumulated in the late stage of the Dongying deposition to form a reservoir,which is a key period for the accumulation of oil in the eastern Qing Dynasty.According to the analysis of the dynamic and static characteristics of the reservoir,the reservoir formation model of the E₃s₁ is established.The E₃s₁ has the conditions for the formation of structural-lithologic oil reservoirs.The sand body serves as the main transport carrier.Crude oil converges in high structural parts.Based on the aforementioned research,the main controlling factors in the study area are analyzed,and it is considered that the reservoir,caprock and transport system jointly control the formation and distribution of the reservoir.The porosity is 10%;the relationship between the cap layer and the oil and gas properties is that the thicker the layer thickness,the better the oil and gas properties.When the thickness is less than 25m,no industrial oil flow is found,and the lower limit of the control thickness is 25m;The reservoir function shows that the sand-to-sand ratio is positively correlated with oil and gas.When the sand-to-sand ratio is greater than 0.25,the probability of connectivity is greater than 20%.It is considered that the sand body is connected.