摘要：Nuclear magnetic resonance (NMR) is a crucial logging technique for the unconventional and complex reservoir evaluation. However, the echo spacing is always an issue for borehole NMR measurement, which limits the performance of NMR tools when acquiring short relaxation components. In this paper, we proposed a novel Q-switch technique aimed at breaking through the limitation of the dead time of a borehole NMR logging tool, and achieving much shorter echo spacings. Instead of using resistors in parallel with the radio-frequency (RF) coil to reduce the dead time, an inductive-coupling Q-switch circuit was introduced to decrease the ringing-down time significantly after transmitting the RF pulses with a high voltage. The Q-switch circuit consists of an inductive-coupling coil, capacitors, resistors, and active high-voltage MOSFETs. The ringing-down time of the RF system was decreased by at least 10 times compared to a system that did not use the proposed Q-switch scheme, leading to echo spacings lower than 0.3 ms under the condition with a resonant frequency of similar to 500 kHz. Both simulations and experiments were in great agreement, validating the feasibility and efficiency of the proposed Q-switch scheme, which proved to be promising for borehole NMR applications.

关键字：borehole; NMR measurement; dead time; Q-switch; echo spacing; ringing-down; inductive coupling

ISSN号：1742-2132

卷、期、页：卷22期 1: 283-292

发表日期：2025-02-28

期刊分区（SCI为中科院分区）：三区

收录情况：SCI（科学引文索引印刷版）,SCIE（科学引文索引网络版）

发表期刊名称：JOURNAL OF GEOPHYSICS AND ENGINEERING

参与作者：李新,于慧俊

通讯作者：邢天宇,龙志豪,车程

第一作者：罗嗣慧,汪正垛,廖广志,肖立志

论文类型：期刊论文

论文概要：罗嗣慧,李新,于慧俊,汪正垛,邢天宇,龙志豪,车程,廖广志,肖立志，A novel Q-switch technique for ringing-down dissipation of borehole NMR measurement，JOURNAL OF GEOPHYSICS AND ENGINEERING，2025，卷22期 1: 283-292

论文题目：A novel Q-switch technique for ringing-down dissipation of borehole NMR measurement