Open AccessA Practical Method to Compensate for the Effect of Echo Spacing on the Shale NMR T 2 Spectrum
Author(s) -
Ge Xinmin,
Zhao Jier,
Zhang Fengsheng,
Fan Yiren,
Liu Jianyu,
Cai Jianchao,
Nie Shengdong,
Wang Changjiang
Publication year - 2019
Publication title -
earth and space science
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.843
H-Index - 23
ISSN - 2333-5084
DOI - 10.1029/2018ea000540
Subject(s) - oil shale , position (finance) , signal (programming language) , echo (communications protocol) , relaxation (psychology) , amplitude , radius , echo sounding , nuclear magnetic resonance , mineralogy , geology , materials science , physics , computational physics , computer science , optics , remote sensing , psychology , paleontology , computer network , social psychology , computer security , finance , programming language , economics
The low field nuclear magnetic resonance (NMR) technique is considered as one of the most effective methods to characterize the pore size and fluid distribution in geophysical prospecting. The signal of NMR is noninvasive and lithology independent, while the effect of NMR responses influenced by the echo spacing ( T E ) is significant when applied to unconventional reservoirs which are featured with ultralow porosity and pore radius. T E is expected to be as low as possible to ensure most of the hydrogen signals are accounted for, but it is hard to achieve in downhole NMR measurement. We develop a practical method to compensate for the influence of T E on the transversal relaxation time ( T 2 ) spectrum of shale. Based on the experiments with different T E , the relationship between the NMR calibrated porosity and the T E is established to recover the signal amplitude. The effect of T E on the peak position is investigated, and then an empirical equation is constructed to move the peak position to its original state. By the above two‐step correction algorithm, the T 2 spectrums of shale at large T E are compensated precisely. The proposed method provides an effective way to obtain the real T 2 spectrum and achieves good results in the downhole NMR data processing of shale reservoir.