Determination Of The Lower Limit Of Effective Physical Properties Of Low Permeability Reservoir And Its Classification Method

The low-permeability reservoir has complex pore structure,low porosity,low permeability and strong heterogeneity.It is difficult to classify reservoirs.Carrying out reservoir effectiveness evaluation and reservoir classification research are of great significance for the review of old wells in the study area,the search for new high-quality reservoirs,and the improvement of production.The main research area of this paper is the B area of Fushan depression in Hainan.Using core analysis data,mercury intrusion experimental data,and nuclear magnetic resonance T₂ spectral data,The main controlling factors of the pore structure of the study area and the lower limit of the effective physical properties of the reservoir were determined,and different reservoir classification methods were developed based on the capillary pressure curve and the nuclear magnetic resonance T₂ spectrum.By analyzing physical properties,scanning electron microscopy,and casting thin sections,the main influencing factors of pore structure are intergranular contact properties.The minimum effective pore throat radius method,minimum radius of curvature method,displacement pressure inflection point method and cumulative frequency statistical method were used to determine the lower limit of effective physical properties of reservoirs in B area.Correlation analysis was carried out on the pore structure parameters obtained by mercury intrusion experiment.Five parameters of maximum pore throat radius,median pore throat radius,average pore throat radius,sorting coefficient and porosity were selected to construct reservoir classification index A_MICP.Using NMR T₂ spectral data,the parameters of large and small pores were extracted by Gaussian distribution function,and the parameters of macroporous components were selected to construct reservoir classification index A_NMR.Different classification criteria were established for the classification indexes obtained by the two methods,and the conventional logging data were obtained to obtain the corresponding A₁ and A₂,respectively.The purpose of using conventional logging data for reservoir classification was achieved.