An NMR log echo data de-noising method based on the wavelet packet threshold algorithm

作者：Meng, Xiangning^*; Xie, Ranhong; Li, Changxi; Hu, Falong; Li, Chaoliu; Zhou, Cancan

来源：Journal of Geophysics and Engineering, 2015, 12(6): 956-968.

DOI：10.1088/1742-2132/12/6/956

• NMR log signal
• wavelet packet threshold algorithm
• SNR improvement
• wavelet packet basis
• decomposition scale

To improve the de-noising effects of low signal-to-noise ratio (SNR) nuclear magnetic resonance (NMR) log echo data, this paper applies the wavelet packet threshold algorithm to the data. The principle of the algorithm is elaborated in detail. By comparing the properties of a series of wavelet packet bases and the relevance between them and the NMR log echo train signal, 'sym7' is found to be the optimal wavelet packet basis of the wavelet packet threshold algorithm to de-noise the NMR log echo train signal. A new method is presented to determine the optimal wavelet packet decomposition scale; this is within the scope of its maximum, using the modulus maxima and the Shannon entropy minimum standards to determine the global and local optimal wavelet packet decomposition scales, respectively. The results of applying the method to the simulated and actual NMR log echo data indicate that compared with the wavelet threshold algorithm, the wavelet packet threshold algorithm, which shows higher decomposition accuracy and better de-noising effect, is much more suitable for de-noising low SNR-NMR log echo data.

• 出版日期2015-12
• 单位中国石油天然气股份有限公司勘探开发研究院; 中国石油大学（北京）; 油气资源与探测国家重点实验室