地球物理学进展 ›› 2021, Vol. 36 ›› Issue (5): 2082-2089.doi: 10.6038/pg2021FF0244

• 应用地球物理学Ⅰ(油气及金属矿产地球物理勘探) • 上一篇    下一篇

磁场强度对T2-T1二维核磁共振实验的影响研究

覃莹瑶1(), 张宫1,*(), 张嘉伟2, 张家成1, 刘洋1, 李森1   

  1. 1.长江大学油气资源与勘探技术教育部重点实验室,武汉 430100
    2.中海油田服务股份有限公司油田技术研究院,北京 101149
  • 收稿日期:2021-05-26 修回日期:2021-09-05 出版日期:2021-10-20 发布日期:2021-11-11
  • 通讯作者: 张宫 E-mail:qinyyao@163.com;zhanggong@yangtzeu.edu.cn
  • 作者简介:覃莹瑶,女,1997年生,硕士研究生,主要从事核磁共振弛豫机制与岩心实验研究.E-mail: qinyyao@163.com
  • 基金资助:
    国家科技重大专项(2017ZX05019003-002)

Study on the influence of magnetic field intensity on T2-T1 two-dimensional nuclear magnetic resonance experiment

QIN YingYao1(), ZHANG Gong1,*(), ZHANG JiaWei2, ZHANG JiaCheng1, LIU Yang1, LI Sen1   

  1. 1. Key Laboratory of Exploration Technologies for Oil and Gas Resources of Education Ministry of Yangtze University, Wuhan 430100, China
    2. China Oilfiled Services Limited, Well-Tech R&D Institute, Beijing 101149, China
  • Received:2021-05-26 Revised:2021-09-05 Online:2021-10-20 Published:2021-11-11
  • Contact: ZHANG Gong E-mail:qinyyao@163.com;zhanggong@yangtzeu.edu.cn

摘要:

多维核磁共振测井比一维核磁包含更多的观测信息,往往可以解决单独使用横向弛豫时间(T2)进行测井评价时遇到的困难,在非常规油气储层勘探开发中发挥着不可替代的作用.T2-T1二维核磁共振能够检测页岩中的类固体有机质等含氢化合物,对于确定页岩储层流体成分至关重要,已经成为核磁测井和岩石物理实验的研究热点.与一维核磁共振相比,T2-T1二维核磁实验结果对测量参数更加敏感,已有学者对回波间隔(TE)、等待时间(TW)、扫描次数(SCAN)、回波个数(NECH)对实验结果的影响开展了深入研究,但磁场强度对T2-T1二维核磁的影响尚未见报道.对不同种类样品分别进行0.5 T、0.05 T两种磁场强度(对应共振频率分别为21 MHz、2 MHz)下的T2-T1二维核磁共振实验,分析了磁场强度对实验结果的影响,研究表明:对于自由溶液,纵向弛豫时间(T1)对磁场强度更加敏感,磁场强度增大时,自由溶液T1增大、T2不变,T2-T1谱流体信号向上移动;对于实际岩样,受内部磁场梯度的影响,磁场强度增大时,T1增大、T2减小,T2-T1谱中流体信号向左上方移动.定量刻画了不同弛豫组分在磁场强度变化时谱峰位置的变化规律,能够将实验室得到的页岩油高频核磁流体识别图版转换为测井资料的低频流体识别图版,为二维核磁共振测井表征储层流体成分信息提供了理论依据.

关键词: 核磁共振, T2-T1, 磁场强度, 共振频率

Abstract:

Multidimensional Nuclear Magnetic Resonance (NMR) logging contains more observation information than one-dimensional NMR logging.With the help of multidimensional information, the difficulties encountered in logging evaluation using lateral relaxation time (T2) alone can often be solved, and it plays an irreplaceable role in exploration and development of unconventional oil and gas reservoirs.T2-T1 two-dimensional NMR can detect hydrogen-containing compounds such as solid-like organic matter in shale, which is very important to determine the fluid composition of shale reservoir and has become a research hotspot in NMR and petrophysical experiments.Compared with 1D NMR, the experimental results of T2-T1 2D NMR are more sensitive to the measured parameters.The influence factors of echo interval (TE), waiting time (TW), number of scans (SCAN), and number of echoes (NECH) on experimental results has been thoroughly investigated, but the effect of magnetic field intensity on T2-T1 2D NMR has not been reported.T2-T1 2D NMR experiments were carried out on different types of samples at two magnetic field strengths of 0.5 T and 0.05 T (corresponding to resonance frequencies of 21 MHz and 2 MHz), respectively, and the influence of magnetic field intensities on T2-T1 2D NMR experiment results was analyzed.The results show that the longitudinal relaxation time (T1) is more sensitive to the magnetic field strength for free solution.When the magnetic field intensity increases, the free solution T1 increases, T2 remains unchanged, and the T2-T1 spectrum fluid signal moves upward.For core samples, under the influence of internal magnetic field gradient, when the magnetic field intensity increases, T1 increases, T2 decreases, and the fluid signal in T2-T1 spectrum moves to the left and upper.Quantitatively depicts the variation law of spectral peak positions of different relaxation components when the magnetic field intensity changes, and can convert the high-frequency nuclear magnetic fluid identification chart of shale oil obtained in the laboratory into the low-frequency fluid identification chart of logging data, which provides a theoretical basis for 2D NMR logging to characterize reservoir fluid composition information.

Key words: Nuclear magnetic resonance, T2-T1, Magnetic field intensity, Resonance frequency

中图分类号: