Field experiment provides ground truth for surface nuclear magnetic resonance measurement
Field experiment provides ground truth for surface nuclear magnetic resonance measurement
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DOI：
10.1029/2011gl050167
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发表时间：
2012-02
影响因子：
5.2
通讯作者：
R. Knight;E. Grunewald;T. Irons;K. Dlubac;Yi-Qiao Song;H. Bachman;B. Grau;D. Walsh;J. Abraham;J. Cannia
中科院分区：
文献类型：
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作者：
R. Knight;E. Grunewald;T. Irons;K. Dlubac;Yi-Qiao Song;H. Bachman;B. Grau;D. Walsh;J. Abraham;J. Cannia
淡水资源可持续管理的需求是 21 世纪的巨大挑战之一。由于地球上大部分液态淡水以地下水形式存在，因此开发非侵入性地球物理技术来表征地下水含水层至关重要。在美国中部高原含水层进行了现场实验，以探索非侵入性表面核磁共振 (SNMR) 技术的控制机制。我们在现场获取了 SNMR 数据和测井 NMR 数据，以及来自钻屑的岩性信息。这使我们能够直接将测井期间测量的 NMR 弛豫参数 T2 与使用 SNMR 方法测量的弛豫参数 T2* 进行比较。后者可能受到磁场不均匀性的影响，从而模糊了 NMR 弛豫参数与地质材料的水力传导率之间的联系。当测井 T2 数据转换为伪 T2* 数据时，通过考虑磁场的不均匀性和仪器停滞时间，我们发现与从 SNMR 测量获得的 T2* 非常吻合。这些结果与现场岩性的附加信息相结合，使我们能够描述控制 SNMR 测量的物理机制。这种理解是发展 SNMR 作为评估地下水资源的可靠地球物理方法的关键一步。
The need for sustainable management of fresh water resources is one of the great challenges of the 21st century. Since most of the planet's liquid fresh water exists as groundwater, it is essential to develop non‐invasive geophysical techniques to characterize groundwater aquifers. A field experiment was conducted in the High Plains Aquifer, central United States, to explore the mechanisms governing the non‐invasive Surface NMR (SNMR) technology. We acquired both SNMR data and logging NMR data at a field site, along with lithology information from drill cuttings. This allowed us to directly compare the NMR relaxation parameter measured during logging,T2, to the relaxation parameter T2* measured using the SNMR method. The latter can be affected by inhomogeneity in the magnetic field, thus obscuring the link between the NMR relaxation parameter and the hydraulic conductivity of the geologic material. When the logging T2data were transformed to pseudo‐T2* data, by accounting for inhomogeneity in the magnetic field and instrument dead time, we found good agreement with T2* obtained from the SNMR measurement. These results, combined with the additional information about lithology at the site, allowed us to delineate the physical mechanisms governing the SNMR measurement. Such understanding is a critical step in developing SNMR as a reliable geophysical method for the assessment of groundwater resources.