Study On The Characteristics Of Oil And Water Percolation In Chang 2 Low Permeability Reservoir

The study area is located in the eastern part of the Ordos basin with a block area of 13km~2.And the production of the study area is Chang2 oil formation.It is a typical low porosity and low permeability reservoir where the pores are small and the connectivity is poor.The percolation does not conform to Darcy's law,and the flow of fluid in the reservoir has start-up pressure.Unclear understanding of the oil-water percolation law in the study area is the main reason for low water recovery,low oil recovery rate and rapid decline in production.Therefore,it is very important to clarify the characteristics of oil and water percolation in the study area,which is also the main problem facing the research area.On the basis of the previous research,the study on the start-up pressure of two phase percolation is carried out in accordance with the geological and reservoir characteristics of the study area and the analysis of the experimental data of the percolation.The influence of different percolation parameters on the size of the two phase starting pressure is analyzed.The function relation expression of relationship among the two phase start-up pressure of the study area,the water saturation and the permeability of the rock sample is established.The relative permeability curves of low permeability rock samples in the study area are measured by the steady state method.On this basis,the article analyzesand studies the process and applicability of the 4 commonly used methods for the normalization of Relative permeability curves,thenoptimizes the polynomial fitting method as the normalization method for normalizing the relative permeability curves in the study area,and the law of percolation and the influencing factors of the oil-water two phases in the study area are analyzed.The study shows that the bound water saturation of the study area is as high as 48%,the residual oil saturation is about28%,the two-phase flow interval is narrow,the average water saturation is about 63%,the oil and water relative permeability is 0.12,the oil phase permeability decreases rapidly and the water phase permeability is slowly rising,and the wettability of reservoir rock is now wetting.The relative permeability curve of the study area,the ratio curve of phase infiltration and the relationship between water production rate and water saturation is synthetically analyzed,and the characteristics of oil and water percolation and the law of water content change in the study area are clarifies:with the increase of water saturation,the water yield of the study area is increased.Within different water saturation ranges,the rate of increase in water yield is different.The average water saturation of the study area is about 63%.It is suggested that measures should be taken to increase production pressure differential.