Evaluation Method of Dense Sandstone Reservoir Based on NMR Logging Pore and Throat Distribution

Q area in Sichuan Basin is an important area for exploration and development of tight gas, however the reservoir pore structure is complex, the vertical variation is fast and the reservoir quality evaluation is difficult, which makes it difficult in choosing the box of horizontal wells. At the same time, the traditional core pore-permeability relationship, the permeability formulas of TimurCoates and NMR logging are not accurate enough to meet the needs of production practice. In order to evaluate reservoir type and permeability with logging data, this paper analyzes the response characteristics of NMR logging in the second member of Shaximiao Formation in Q area of Sichuan Basin, combines the conventional logging and array induction data of different reservoirs and optimizes reservoir classification parameters such as effective porosity, shale content, resistivity increase rate and macropore ratio. Furthermore, suggestions on horizontal well box design are put forward for reservoir classification evaluation and optimization of highquality reservoir in the target formation of the second member of Shaximiao Formation. According to the results analyzed through the relationship between throat proportions and permeability, a permeability calculation method based on pore throat distribution of NMR logging is proposed to evaluate reservoir permeability. The application results show that reservoir logging classification method effectively evaluates the heterogeneity of reservoir, and the permeability calculated by the method based on the pore throat distribution of NMR logging is in good agreement with the pore permeabiltiy, the accuracy of calculation is higher than that of core porepermeability correlation method and Timur-Coates and SDR methods.