A new method for permeability estimation using integral transforms based on NMR echo data in tight sandstone

Permeability is a vital petrophysical parameter in reservoir evaluation and productivity prediction. In this study, a new method is presented to estimate permeability in tight sandstone using integral transforms of the NMR echo data. Different permeability indicators are directly computed from the NMR echo data using integral transforms without obtaining T2 distributions by inversion of the echo data which is usually an indispensable part in traditional NMR-based methods for permeability estimation. The forms of these permeability indicators are controlled by the parameter n. Furthermore, new empirical models are developed based on the permeability indicators to estimate the permeability of tight sandstone. Different from the fixed permeability characterization parameters used in traditional models, in the new models, more suitable parameters can be selected to characterize the rock permeability by optimizing the parameter n. The numerical simulation results show that the integral transform method is simpler, more stable, and more accurate than the traditional T2 inversion-based methods for permeability indicator computation and is still effective for low signal-to-noise ratio echo data. The core experiments and permeability estimation results indicate that the proposed method is superior to the traditional Schlumberger-Doll Research (SDR) method for permeability estimation in tight sandstone.