A Novel Method to Predict the Permeability of Heterogeneous Sandstones Using Multiple Echo Spacing NMR Measurements

Abstract

We propose a novel method for estimating the permeability of heterogeneous sandstones based on the nuclear magnetic resonance (NMR) data with multiple echo spacings. The decaying curves and their corresponding spectra are obtained for different echo spacings to investigate the relaxation property, the diffusion term, and the signal loss contributed by higher echo spacing. Moreover, an empirical model is developed to correlate permeability with the differential decay rate. The result shows that the geometric transversal relaxation time is positively related to echo spacing, which disobeys the traditional cognition. Moreover, the absolute value of the differential decay rate is positively correlated with the echo spacing and exhibits a power law behavior. More interestingly, it is observed that the permeability diminishes in a power law behavior with respect to fitting parameters. This marks the first attempt to establish a relationship between the permeability and NMR data with different echo spacings, which is hopeful to be extended to other complex reservoirs with the availability of multiple echo spacing data.