The Study On Microscopic Pore Structure And Percolation Characteristics Of Diagenetic Facies In Chang 4+5 Reservoir Of Wangpanshan Area,Jiyuan Oilfield

The practical experience in the exploration and development of Jiyuan oilfield shows that the microscopic characteristics of the reservoir in the study area are very complicated.With the characteristics of strong heterogeneity,small pore throat,complicated structure and outstanding Jamin effect,etc.These problems lead to the difficulty of oilfield development and the low degree of recovery,which seriously restrict the stable production of the oil field.This paper based on the basic geological data,divide the diagenetic facies of reservoir,analyze the percolation capacity and actual production performance of each diagenetic facies.The main results are as follows:(1)The Chang 4+5 reservoir in Jiyuan oilfield is mainly developed delta front facies sedimentary.The rock types are mainly very fine-fine feldspar sandstone and lithic feldspar sandstone,medium composition maturity,and clay mineral development.(2)The reservoir diagenetic stage in late diagenetic period A,part of entering into early diagenetic period B.Divided into six diagenetic facies types: kaolinite chlorite cementation-intergranular pore phase,Illite cementation-dissolved pore phase,chlorite kaolinite cementation-dissolved pore phase,kaolinite cementation-dissolved pore phase,kaolinite cementation-dissolved pore intergranular phase,carbonate cementation dense phase.(3)The pore and throat characteristics of different diagenetic facies are different,and the size and distribution of radius play an important role in controlling the pore structure.The kaolinite chlorite cementation and intergranular pore facies are the best diagenetic facies reservoirs in the study area.A large number of effective pores in the reservoir are connected by the coarse throat and the fluid is easy to flow,so the overall permeability of the reservoir is higher;on the contrary,the smaller the pores and the throat,the worse the physical properties of the reservoir.(4)The movable fluid characteristics of different diagenetic facies reservoirs are different.The movable fluid saturation is mainly controlled by the volume and distribution of the effective throat,and the effective throat of kaolinite chlorite cementation and intergranular pore facies is thick,so that the fluid can easily pass through the large throat channel.Therefore,the saturation of movable fluid is high.The cementation of carbonate rock in the tight carbonate cemented reservoir results in extremely low porosity,and the small throat radius makes the fluid bound in the narrow channel,which results in the decrease of the saturation value of the movable fluid in the sample.(5)Combined with the experimental data of facies permeability and actual production data,the diagenetic facies reservoir has the advantages of larger pore throat space,lower displacement pressure,higher connectivity and lower degree of interference between oil and water phases.It provides a good reservoir space and seepage condition for the fluid,so the stable production time is long,the development efficiency is high;the poor diagenetic facies pore throat is poor,the heterogeneity is strong,and the oil-water two phase interference is strong,which leads to the low recovery during the development process.