Application of improved Indonesia saturation equation in low porosity and permeability reservoirs in Daqing Placanticline

In F formation of Daqing placanticline,analysis result of reservoir characters has shown that the formation has low porosity,low permeability,high shale content,more microscopic capillary pore and high irreducible water saturation.The main factors of rock conductance in low porosity and permeability reservoirs are analyzed from theoretically and experimentally.The result shows that conductivity of the reservoirs is mainly influenced by excessive conductivity of shale and irreducible water.Considering the differences of conductance paths between the free water and irreducible water,and based on derivation rules of three-water conduction theory,an equivalent conductivity equation of mixed water is established.Indonesia saturation equation,once applied in reservoirs with fresh water and high shale content,is considered to be improved,since the salinity of the formation water is low and shale content is high in F formation.By replacing water conductivity in Indonesia saturation equation with mixed water equivalent conductivity,a new water saturation model for low porosity and permeability shaly sand reservoirs in Daqing placanticline is established in this paper.The parameters of interpretation model including shale content,porosity,irreducible water saturation etc.are determined by multiple regression method with core analysis data and log data.The saturation exponent and cementation exponent in the model are determined from core experimental data with an optimization technology.Compared with well test results and core analysis water saturation in sealed coring well,the results show that the new saturation equation can be applied in evaluation of low porosity and permeability shaly sand reservoirs in F formation with good precision quantitatively.