Comparison of saturation models in application for low porous and permeable reservoirs

Saturation evaluation of complex pore structures in reservoirs with low porosity and permeability remains a tough challenge in logging field.The investigation into the characters of porosity,permeability,shale content and pore structure in F formation of Chao-Chang area of Daqing concludes that the reservoirs are characterized by low porosity,low permeability,high shale content,more microscopic capillary pores and high irreducible water saturation.This paper introduces a symmetrical effective medium conductance theory based on the reservoir characters of F formation,and proposes a new effective medium conductivity model.The paper presents an improved Indonesia saturation equation and Doll equation and describes an analysis of the theoretical characteristics of three models and Archie equation and comparison of the calculated saturation results from the four models with the results in three sealed coring well.The contrast shows that the effective medium conductivity model,capable of more consideration factors,and with the minimum average relative error of water saturation,lends itself better to evaluation of the hydrocarbon saturation in argillaceous sandstone reservoir with low porosity and permeability.