Sduty On Pore Structure And Percolation Characteristics Of Dainan Formation Low Permeability Reservoirs In Yongan Area,Gaoyou Sag

Low permeability pore throat,small pore structure,strong heterogeneity and micro seepage mechanism are different from conventional reservoir,so the pore structure and seepage characteristics of low permeability reservoir are studied.Based on the pressure gradient of single phase flow,the relative permeability of oil and water,and the experimental results of water flooding,the percolation rule of low permeability reservoir is revealed.According to the research,the main results are as follows:The throat of the low permeable reservoir is small in Yongan area.The correlation between homogenization coefficient,permeability and average throat radius is poor,which is obviously different from medium high permeability reservoir;The sorting coefficient is positively related to permeability and average throat radius.The pore structure coefficient,expulsion pressure and permeability or mean throat radius are negatively related.The correlation between mercury removal efficiency and permeability average,throat radius is poor.Study on single-phase seepage flow in low permeability reservoir in Yongan oilfield.The all core samples have the minimum starting pressure gradient.The lower the core permeability is,the larger the starting pressure gradient is.The minimum?pseudo?startup pressure gradient of low permeability reservoir has a good correlation with the pseudo fluid mobility of the fluid,and which presents a better power function relationship.The characteristics of relative permeability curve of low permeability reservoir are defined.The anomalous forms of relative permeability curves in low permeability reservoirs are mainly water phase linear type and water phase depression type.The main reasons for abnormal formation are as follows:the poor porosity and permeability conditions of low permeability reservoirs,liquid blocking effect,the influence of clay mineral composition and occurrence.The NMR T₂ spectrum can well reflect the mobile fluid content in the rock core.The movable resources of low permeability reservoirs in Yongan are evaluated by using nuclear magnetic resonance movable fluid and the starting pressure,the result isverified by actural production,which provides an important basis and support for the development of low permeability reservoirs in Jiangsu Oilfield.