Research On Reservoir Geological Modeling And Remaining Oil Distribution Of Chang4+5 Formation Of A Well Area In Northern Shaanxi Wuqi Oilfield

The well area A in the Wuqi Oilfield is located in Baibao Township of Wuqi County in the south-central of Northern Shanxi Slope.The structure is gentle and has a strong heterogeneity.It is a low-porosity and low-permeability structural-lithologic reservoir.The Chang 4+5 reservoir is the main reservoir in the oil field,with the original proven geological reserves of 8.01 million tons.Since the beginning of production,the average annual decline rate of production is 21%and the overall mining rate is 15%.The oil field still contains a large amount of remaining oil and the distribution characteristics of the remaining oil and the direction of potential tapping are not yet clear.Therefore,this paper uses the well logging data and sedimentary background to carry out geological modeling of the Chang 4+5 reservoir.On this basis,the distribution characteristics of remaining oil is obtained by the method of reservoir numerical simulation,and finally we summarize the factors of controlling the remaining oil.Get the following points:?1?The Chang 4+5 is divided into three small layers of Chang 4+5₁,Chang 4+5₂¹,and Chang 4+5₂².The Chang 4+5₁ and Chang 4+5₂¹ mainly develop distributary bay,with some subaqueous distributary channels in them.The average thickness of Chang 4+5₁ sand-body is8.5m,and the average thickness of Chang 4+5₂¹ sand-body is 3.8m.The Chang 4+5₂²reservoir mainly develops two northeast-southwest direction subaqueous distributary channels.The bottom of the reservoir develops a series of sand-bodies with good continuity and the average thickness of sand-bodies is 10.8m.?2?The comparison of the studies of coefficient of permeability variation,permeability max-mean ratio,permeability ratio,vertical granularity,and the calculation of inter-layer heterogeneity parameters show that Chang 4+5₂² reservoir has lower heterogeneity than the Chang 4+5₁ and Chang 4+5₂¹ reservoirs.?3?Use the shale content to establish a lithofacies model and use the phase control method to establish a property model.Using the model for reserves calculation,the Chang 4+5geological reserves in the study area is 881.824×10⁴t.In the Chang 4+5 of the study area,the Chang 4+5₁ reserves is 284.31×10⁴t,the Chang 4+5₂¹ reserves is 94.6×10⁴t,and the l Chang4+5₂² reserves is 502.914×10⁴t.?4?Use the roughened attribute model for numerical simulation to obtain the remaining oil distribution characteristics.The overall distribution characteristics of the remaining oil are the same as the location of the distributary channel.The result shows a NE-directional remaining oil distribution zone and a higher remaining oil content in the local high-microstructure sections.?5?According to the characteristics of the remaining oil distribution,it is found that the sedimentary microfacies in the study area is the main factor for controlling the distribution of remaining oil and the heterogeneity of the reservoir is the microscopic factor for the remaining oil distribution.A large amount of remaining oil is formed in the partial microstructural high sites,and the remaining oil content is higher in the areas where there is no production well.