Hu Bill X, Meerschaert Mark M, Barrash Warren, Hyndman David W, He Changming, Li Xinya, Guo Luanjing
Department of Geological Sciences, Florida State University, Tallahassee, FL 32306, USA.
J Contam Hydrol. 2009 Sep 1;108(3-4):77-88. doi: 10.1016/j.jconhyd.2009.06.001. Epub 2009 Jun 27.
It is widely recognized that groundwater flow and solute transport in natural media are largely controlled by heterogeneities. In the last three decades, many studies have examined the effects of heterogeneous hydraulic conductivity fields on flow and transport processes, but there has been much less attention to the influence of heterogeneous porosity fields. In this study, we use porosity and particle size measurements from boreholes at the Boise Hydrogeophysical Research Site (BHRS) to evaluate the importance of characterizing the spatial structure of porosity and grain size data for solute transport modeling. Then we develop synthetic hydraulic conductivity fields based on relatively simple measurements of porosity from borehole logs and grain size distributions from core samples to examine and compare the characteristics of tracer transport through these fields with and without inclusion of porosity heterogeneity. In particular, we develop horizontal 2D realizations based on data from one of the less heterogeneous units at the BHRS to examine effects where spatial variations in hydraulic parameters are not large. The results indicate that the distributions of porosity and the derived hydraulic conductivity in the study unit resemble fractal normal and lognormal fields respectively. We numerically simulate solute transport in stochastic fields and find that spatial variations in porosity have significant effects on the spread of an injected tracer plume including a significant delay in simulated tracer concentration histories.
人们普遍认识到，天然介质中的地下水流和溶质运移在很大程度上受非均质性控制。在过去三十年中，许多研究考察了非均质水力传导率场对水流和运移过程的影响，但对非均质孔隙度场的影响关注较少。在本研究中，我们利用博伊西水文地球物理研究站点（BHRS）钻孔中的孔隙度和粒径测量数据，来评估表征孔隙度和粒径数据的空间结构对于溶质运移建模的重要性。然后，我们基于钻孔测井中相对简单的孔隙度测量和岩芯样品的粒径分布，开发合成水力传导率场，以检验和比较包含和不包含孔隙度非均质性情况下示踪剂在这些场中的运移特征。特别是，我们基于BHRS中一个非均质性较小的单元的数据开发水平二维模型，以考察水力参数空间变化不大时的影响。结果表明，研究单元中的孔隙度分布和导出的水力传导率分别类似于分形正态场和对数正态场。我们对随机场中的溶质运移进行了数值模拟，发现孔隙度的空间变化对注入示踪剂羽流的扩散有显著影响，包括模拟示踪剂浓度历史出现显著延迟。
