地球物理学进展 ›› 2019, Vol. 34 ›› Issue (2): 622-627.doi: 10.6038/pg2019CC0067

• 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

低温SQUID瞬变电磁法中去除地磁场影响的方法研究

裴易峰1,荣亮亮1,张懿1,殷长春2,*(),伍俊1,王远3,谢晓明1   

  1. 1. 中国科学院上海微系统与信息技术研究所,上海 200050
    2. 吉林大学地球探测科学与技术学院,长春 130026
  • 收稿日期:2018-07-03 修回日期:2019-01-27 出版日期:2019-04-20 发布日期:2019-05-13
  • 通讯作者: 殷长春 E-mail:yinchangchun@jlu.edu.cn
  • 作者简介:裴易峰,男,1989年生,硕士,主要从事超导电磁方法研究.(E-mail:peiyifeng@mail.sim.ac.cn)
  • 基金资助:
    国家自然科学基金重点项目(41530320);面上项目(41774125);上海市科学技术委员会科研计划项目联合资助.(7511103300)

Removal of geomagnetic field in low-temperature SQUID TEM

PEI Yi-Feng1,RONG Liang-liang1,ZHANG Yi1,YIN Chang-chun2,*(),WU Jun1,WANG Yuan3,XIE Xiao-ming1   

  1. 1. Shanghai Institute of Microsystem and Information Technology(SIMIT),The Chinese Academy of Sciences, Shanghai 200050,China
    2. College of Geo-exploration Science and Technology, Jilin University, Changchun 130026, China3. College of Instrumentation and Electrical Engineering, Jilin University, Changchun 130026, China
  • Received:2018-07-03 Revised:2019-01-27 Online:2019-04-20 Published:2019-05-13
  • Contact: Chang-chun YIN E-mail:yinchangchun@jlu.edu.cn

摘要:

采用低温SQUID(Superconducting Quantum Interference Device)进行瞬变电磁测量,具有高灵敏度的优势,但易受到地磁场的影响.由于地磁场变化为nT量级,而低温SQUID灵敏度可达10 fT/ Hz .使用传统的双极性脉冲激励叠加对地磁场的抑制作用有限.当晚期道二次场信号叠加了地磁场信号后,导致晚期道信号发生整体抬升或降低,甚至出现负值,使得晚期道信号无法直接利用,从而直接影响勘探深度.本文研究不同噪声环境下信号叠加对噪声压制的机理,并结合地磁场的特点,对off-time晚期道噪声段进行一次线性拟合,获得近似地磁场变化规律,并通过外推得到整个off-time地磁场干扰,最终去除off-time信号中的地磁场.去除地磁场后晚期道瞬变电磁信号信噪比明显改善,勘探深度得到较大提高.

关键词: 瞬变电磁, 低温SQUID, 地磁场, 晚期道, 信噪比

Abstract:

Using Low-Temperature Superconducting Quantum Interference Device(LT SQUID)as B-sensor in transient EM(TEM)measurements, higher magnetic sensitivity has been achieved than the conventional sensors. However, the geomagnetic field can be a serious issue because the geomagnetic field range in nT, while the sensitivity of LT SQUID is about 10 fT/ Hz . The suppression to the geomagnetic field is limited by the conventional stacking of bipolar pulse excitation, thus, when the secondary field signal is mixed with the geomagnetic field signal, it is found that there always exist an offset in the late off-time channels after stacking, making the off-time signal unusable. In this paper, we first study the noise suppression by stacking in different noise environments. Then, we analyze the features of geomagnetic field and after that we propose a polynomial fitting method to correct the geomagnetic field for the whole off-time channels. In this way, we can extend the usable signal to very late time channels, so that the depth of exploration of TEM systems can be improved.

Key words: Transient Electromagnetic(TEM), Low-Temperature Superconducting Quantum Interference Device(LT SQUID), Geomagnetic field, Late-time channels, Signal-noise ratio

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