Study On Original Oil Saturation For Low Porosity And Permeability Sand Reservoirs In Daqing Placanticline

The establishment of reasonable conductivity models is one of the important indexes toevaluate the low porosity and permeability reservoirs. Firstly, in this paper, the reservoircharacters in F formation of Daqing Placanticline are studied, and the analysis result ofreservoir characters has shown that the formation has low porosity, low permeability, highshale content, more microscopic capillary pore, complex pore structure and high irreduciblewater saturation. The conductive law in F formation of Daqing placanticline is studieddetailedly with experimental data in different conditions of nomal-temperature andnomal-pressure, high-temperature and high-pressure, different salinities of formation water.The influence of the temperature, pressure and formation water salinity on the Archieparameters is analyzed, it find out that with the changes of temperature, pressure andformation water salinity the values of m and n are changed. Based on three conductingcomponents of shale, irreducible water and free water, and the different conductance paths ofclay water, free water and irreducible water on rock conductivity is considered, theconnectivity model in F formation of Daqing placanticline is established with the connectivitytheory and the mixing law. By analyzing effects of some facters on the proposed model, wefind out some rules. Resitivity index slightly increases and formation resisitivity decreases asCEC increases. Resitivity index decreases and formation resisitivity increases as resistivity offormation water increases. Resitivity index decreases and formation resisitivity decreases asirreducible water saturation increases. Resitivity index increases and formation resisitivityincreases as the conductivity exponents of the three conducting phases increase. The influenceof water connectivity correction index and the conductivity exponent of each conductivephase on the conductivity rule of the rock are researched. Therefore, according to theconductive character of the area, it concluded that the conductivity exponents of matrix phaseand clay phase are either less than or equal to that of free fluid phase. Also, the conductivityexponent of each phase is determined from core experimental data with an optimizationtechnology. Compared with core analysis water saturation in sealed coring well and well testresults show that the connectivity model can be applied in evaluation of low porosity andpermeability shaly sand reservoirs in F formation with good precision quantitatively.