Abstract: 

Nuclear magnetic resonance (NMＲ) characteristic of hydrates is of great significance for offshore hydrate reservoir exploration and stratigraphic description． The low-field NMＲ experiments were conducted to explore the relaxation response of tetrabutylammonium bromide (TBAB) aqueous solution during the step cooling and heating processes． The transverse relaxation time spectrum is

divided into three intervals: small peak interval (＜ 4 ms) ，medium peak interval (4 ～ 100 ms) and large peak interval (＞ 100

ms),and their NMＲ relaxation signals originate from hydrate，TBAB molecules and water，respectively． Evolution of sample temperature and transverse relaxation time distribution can be used to distinguish the substances contained in the sample，that is，solid hydrate，TBAB aqueous solution，water，and ice． The signal of small peak interval is completely generated by TBAB hydrate，and thus the relationship between the hydrate NMＲ signal (amplitude and T2) and temperature is established，which can be used as a temperature calibration basis for quantitative analysis of hydrate content．

Keywords: low-field nuclear magnetic resonance，transverse relaxation time，amplitude，TBAB hydrate，variable temperature experiment