Permeability prediction based on dual seismic pore structure factors

Abstract

Pore structure, especially pore shape and size, is a key factor affecting reservoir permeability. There is a poor correlation between permeability and porosity when the pore structure is complex, which leads to the low accuracy of permeability prediction by using porosity. In view of the preceding problems, six factors related to pore structure are summarized from rock physical models and entitled seismic pore structure factors (SPSFs), and the sensitivity of SPSF to permeability is analyzed with the data of two groups of clastic rock cores. The results find that the shear Lee factor is most sensitive to permeability, followed by the shear flexibility factor. In addition, there are good linear correlations between the shear Lee factor and pore size and between the shear flexibility factor and pore aspect ratio. Therefore, the combination of the shear Lee factor and pore aspect ratio can better characterize pore structure, and thus reservoir permeability. A seismic permeability prediction method based on pore aspect ratio, the shear Lee factor, and lithofacies is developed and applied to the Jurassic tight sandstone reservoirs of the Sichuan Basin. The results find that the permeability prediction accuracy is within half an order of magnitude, which is five times higher than the single-factor method of the shear flexibility factor. Compared with porosity, permeability distribution is more consistent with the measured productivity, which confirms the effectiveness of the method. It also provides a new way to predict the spatial distribution of reservoir permeability.