Parsekian A D, Dlubac K, Grunewald E, Butler J J, Knight R, Walsh D O
Currently at the Department of Geology and Geophysics, University of Wyoming, 1000 E. University Ave., Laramie, WY.
Ground Water. 2015 Jan-Feb;53(1):111-21. doi: 10.1111/gwat.12165. Epub 2014 Feb 12.
Characterization of hydraulic conductivity (K) in aquifers is critical for evaluation, management, and remediation of groundwater resources. While estimates of K have been traditionally obtained using hydraulic tests over discrete intervals in wells, geophysical measurements are emerging as an alternative way to estimate this parameter. Nuclear magnetic resonance (NMR) logging, a technology once largely applied to characterization of deep consolidated rock petroleum reservoirs, is beginning to see use in near-surface unconsolidated aquifers. Using a well-known rock physics relationship-the Schlumberger Doll Research (SDR) equation--K and porosity can be estimated from NMR water content and relaxation time. Calibration of SDR parameters is necessary for this transformation because NMR relaxation properties are, in part, a function of magnetic mineralization and pore space geometry, which are locally variable quantities. Here, we present a statistically based method for calibrating SDR parameters that establishes a range for the estimated parameters and simultaneously estimates the uncertainty of the resulting K values. We used co-located logging NMR and direct K measurements in an unconsolidated fluvial aquifer in Lawrence, Kansas, USA to demonstrate that K can be estimated using logging NMR to a similar level of uncertainty as with traditional direct hydraulic measurements in unconsolidated sediments under field conditions. Results of this study provide a benchmark for future calibrations of NMR to obtain K in unconsolidated sediments and suggest a method for evaluating uncertainty in both K and SDR parameter values.
含水层水力传导率（K）的表征对于地下水资源的评估、管理和修复至关重要。传统上，K值是通过在井中离散区间进行水力测试获得的，而地球物理测量正成为估计该参数的一种替代方法。核磁共振（NMR）测井技术曾主要用于深层固结岩石石油储层的表征，如今开始应用于近地表未固结含水层。利用一个著名的岩石物理关系——斯伦贝谢多尔研究（SDR）方程，可以根据NMR含水量和弛豫时间估算K值和孔隙率。由于NMR弛豫特性部分取决于磁性矿化和孔隙空间几何形状，而这些都是局部可变的量，因此对SDR参数进行校准对于这种转换是必要的。在此，我们提出一种基于统计的SDR参数校准方法，该方法确定了估计参数的范围，并同时估计了所得K值的不确定性。我们在美国堪萨斯州劳伦斯市的一个未固结河流含水层中，对测井NMR和直接K测量进行了同位置测量，以证明在野外条件下，利用测井NMR可以将K值估计到与未固结沉积物中传统直接水力测量相似的不确定水平。本研究结果为未来在未固结沉积物中利用NMR获取K值的校准提供了一个基准，并提出了一种评估K值和SDR参数值不确定性的方法。
