A Morphological Method for Predicting Permeability of Fractured Tight Sandstone Reservoirs Based on Electrical Imaging Logging Porosity Spectrum

Abstract

Abstract Permeability is crucial for formation evaluation, it reflects the reservoir fluid fluidity, and it directly affects subsequent development and production. In conventional tight sandstone formation, it has proposed many methods to predict reservoir permeability. However, influenced by the heterogeneity of fractured tight sandstone reservoir, the accuracy of permeability calculated by the proposed method is not high, and there has been little research on permeability evaluation for this type of reservoir. it's difficult for conventional wireline logging and nuclear magnetic resonance (NMR) logging to evaluate fracture parameters, but electrical imaging logging can well reflect fracture information. Therefore, we adopted electrical imaging logging to evaluate the permeability of fractured tight sandstone reservoir. We proposed a morphological method to predict permeability: Firstly, the electrical imaging logging data is processed and the formation porosity spectrum is obtained, then the position of primary porosity spectrum peak is determined. Afterwards, extract the mean and standard deviation parameters based on the distribution morphology of the primary porosity spectrum and combine the normal distribution function to fit a single primary porosity spectrum. Accumulate the amplitude of the original porosity spectrum and the fitted primary porosity spectrum respectively. When the cumulative amplitude of the fitted primary porosity spectrum remains basically unchanged, the corresponding porosity is the boundary point between primary pores and secondary pores. Based on this boundary point, the proportion of primary pores in the formation can be calculated. Permeability was influenced by both primary pores and secondary pores in fractured tight sandstone formation, and it has a good correlation with the proportion of primary porosity. Finally, permeability evaluation model is established based on total porosity and matrix pores proportion. The permeability evaluation model was validated using the core physical experimental data of the Triassic Chang63 Member in the Jiyuan area of the Ordos Basin. In formations with underdeveloped fractures, the permeability calculated by this model was close to that calculated directly using total porosity. In formations with fractures, the predicted permeability is more consistent with the permeability analyzed by core experiments compared to the permeability calculated by conventional methods.