Study On NMR Logging Evaluation Of Tight Sandstone Reservoir

Along with the continuous exploration and development of oil and gas in the world,tight oil and gas and other unconventional oil and gas resources have occupied an important position in the world energy structure.Tight sandstone reservoir is characterized by low porosity,low permeability,poor correlation between pore and permeability and complex pore structure,which makes it difficult to evaluate tight sandstone reservoir.The signal collected from NMR log has nothing to do with the rock skeleton,only with the pore fluid in the rock,so NMR log can be used to evaluate the tight sandstone reservoir.In this paper,NMR logging evaluation method of tight sandstone reservoir is studied in order to solve the problems of reservoir parameters and reservoir structure evaluation.Density and NMR logging are combined to calculate porosity,flow unit index is used to calculate permeability,integral transformation is used to extract characteristic parameter PI,and characteristic parameter PI is used to calculate permeability,irreducible water saturation and pore structure,which evades uncertainty of NMR echo data inversion and has good effect in the study area.The NMR logging data are transformed into capillary pressure curve and the pore structure parameters are extracted by the subsection power function transformation method and improved J function transformation method.Based on the cross plot of PI_Cand reservoir quality factor RQI,the classification standard of tight sandstone reservoir is established.The feasibility of the classification method is verified by oil test data.The research results of this paper provide the applicable research methods and ideas for logging evaluation of similar tight sandstone reservoirs.