A Method of Inverting Rock Grain Size Based on Nuclear Magnetic Resonance Logging Data and Application

Abstract

Rock grain size parameter is the key parameter of reservoir rock physics analysis. The study found that the relationship between the NMR $T_2$ spectrum and rock grain size distribution curve is directly related to NMR $T_2$ distribution and grain size distribution of rock, so you can use $T_2$ to retrieve the size distribution of rock NMR spectral data. Based on the calculation of the rock core experiment results of grain size distribution by NMR $T_2$ distribution using the conversion method of piecewise nonlinear calibration for each core, adjusting the calibration parameters to make the grain size distribution calculated with the core analysis of grain size distribution approximation, the error is minimum to obtain each core scale parameter conversion. In the end, the core parameters are classified according to the parameters of pore and permeability. Finally, according to the actual NMR $T_2$ distribution curve inversion of underground rock granularity, the inversion results contrast with the core analysis results, and the reliability of the method is verified to provide accurate, continuous rock size distribution profile analysis of geological reservoir rock physics.