Reservoir Classification Method Based on Three Water Model to Evaluate Low Porosity and Low Permeability Reservoir

Due to the various pore types and complex pore configurations,it is difficult to evaluate low porosity and low permeability reservoir.Slight variation range of porosity often causes large variation range of permeability.According to the shapes of capillary pressure curves of core samples,firstly,the surveyed reservoirs are classified into four types;then calculated are free porosity,micro-porosity and clay porosity in the light of pore radius size;then cast is the percent of each porosity in the total porosities into triangular diagram of porosity classifications to achieve the place of each reservoir on the triangular diagram;the relationships between porosity and permeability in each reservoir are established on the basis of petrophysical data of the core samples;in the end,three types of porosities are obtained from the three water model and are cast into the triangular diagram,from which continual reservoir classification can be gained;then corresponding permeability equations are chosen to compute permeabilities and evaluate reservoir comprehensively.The method is satisfactory in log application.