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《Chinese Journal of Geophysics》 2007-03
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Influence factors of multi-exponential inversion of NMR relaxation measurement in porous media

LIAO Guang-Zhi, XIAO Li-Zhi~, XIE Ran-Hong, FU Juan-Juan Laboratory of NMR Logging, China University of Petroleum, Beijing 102249, China  
Multi-exponential inversion of NMR relaxation signal has been widely used in petroleum industry both in core analysis for petrophysical studies and in logging interpretation for oil exploration. In order to get relaxation time distributions with high resolution in the case of the low SNR, we use the NMR numerical simulation data and experimental data of core analysis to analyze the effects of the number of pre-assigned relaxation bins, the number of spin-echo acquired, and the compression in time domain of the spin-echo trains on the inversions. Meanwhile, in order to find out the influence of SNR for different inversions, the results under different SNR are compared, and the correction methods are improved accordingly. In addition, the influence of SNR to the components with short relaxation times or long relaxation times is discussed in the paper. The results of the study indicate that reducing echoes brings more divergent long T_2 distributions, giving more bins can get higher resolution but take more time for calculation, and data compressing in time domain can increase the calculating speed but does not change the shape of T_2 distribution significantlies, the different algorithms have different sensitivity to the signal-to-noise ratio and using some adjustable parameters to correct the influence is a possible way to improve the inversion quality.
【Fund】: 国家“973”项目(2006CB202306);; 国家自然科学基金项目(90510004)资助
【CateGory Index】: P631.84
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