Experimental and computational investigations of subsurface heterogeneity and contaminant distributions in complex geologic media

地下在多个尺度上是不均匀的，这是规律而不是例外。关于流动和输运参数的空间变异性的信息通常是通过小尺度测量的地质统计分析获得的。尽管地质统计学方法被广泛使用，但尚不清楚它是否能保存地质特征、它们的连通性和形态，这些特征对流体流动，更重要的是，对污染物的运移有很大的影响。我们最近在利用水力层析成像绘制水力导电性(K)和比储（Ss）非均质性方面取得了重大进展。水力层析成像包括从封隔段连续抽取水，并对附近井眼内跨式封隔器系统的水头变化信息进行相应的监测。以层析方式抽取和收集水头变化数据，可以获得有关压力变化在含水层中从各个方向传播的信息。该信息随后用于计算K和Ss层析图的随机逆模型。本课题组在实验室进行的水力层析成像实验表明，它可以比克里格成像更好地显示K和s的分布及其连通性。该方法最近已扩展到包括划分示踪剂传输信息，以成像致密非水相液体（DNAPL）饱和度的三维位置。初步结果表明，DNAPL饱和度及其池可以准确成像。源区DNAPL饱和度的准确成像将大大提高我们在加拿大和其他地区修复数千个站点的能力。建议的研究重点是进行互补的实验和计算调查，这将大大提高我们在复杂地质介质中绘制地下非均匀性和污染源区域的能力。这些能力的发展也将使我们能够大大提高我们对这种介质中的流动和运输过程的基本理解。

The subsurface is heterogeneous at multiple scales and this is the rule rather than the exception. Information about spatial variability of flow and transport parameters is most commonly obtained through geostatistical analysis of small-scale measurements. Despite its common use, it is unclear whether the geostatistical approach can preserve geological features, their connectivity and morphology which can have large impacts on fluid flow and more importantly, contaminant transport. We have recently made significant strides in mapping hydraulic conductivity (K) and specific storage (Ss) heterogeneity using hydraulic tomography. Hydraulic tomography involves the sequential pumping of water from packed-off intervals and the corresponding monitoring of head change information in straddle-packer systems in nearby boreholes. Pumping and collection of head change data in a tomographic manner allows one to obtain information on the propagation of pressure changes through the aquifer from various directions. This information is then used in a stochastic inverse model that computes K and Ss tomograms. Hydraulic tomography experiments performed in the laboratory by our group show that it can image the distributions of K and Ss as well as their connectivity considerably better than kriging. The approach has been recently extended to include partitioning tracer transport information to image the locations of Dense Nonaqueous Phase Liquid (DNAPL) saturations in 3-D. Preliminary results show that DNAPL saturations and their pools can be imaged accurately. Accurate imaging of DNAPL saturations in source zones will considerably improve our abilities to remediate thousands of sites in Canada and beyond. The proposed research focuses on conducting complementary experimental and computational investigations that should significantly advance our capabilities to map subsurface heterogeneity and contaminant source zones in complex geologic media. Development of these capabilities will also allow us to significantly advance our fundamental understanding of flow and transport processes in such media.