Calculation of grain size distribution using NMR T2 spectrum and digital rock technology

Key words:  nuclear magnetic logging  grain size distribution  digital rock  nuclear magnetic resonance simulation  nuclear magnetic resonance T₂ spectrum

Abstract:

A new method calculating grain size distribution (GSD) was proposed by using nuclear magnetic resonance (NMR) T₂ spectrum and digital rock technology. The curve of GSD is approximately consistent with Weibull distribution, so different GSD can be obtained by changing the parameters of Weibull distribution. According to the initial Weibull distribution, digital rock was constructed by process-based method, and then NMR simulation was conducted on this model by random walk method. To go through the parameter region of Weibull distribution makes the simulated T₂ spectrum approach the measured one. The Weibull distribution determined by these parameters was the GSD of rock. The method was used to calculate the GSD of underground rock continuously based on NMR logging. The simulated results agree well with the experimental results and validate the accuracy of this method.