Abstract Characterization of dense non-aqueous phase liquid (DNAPL) distribution is important to facilitate the decision of remediation strategies. However, it is still a great challenge to characterize DNAPL source zone architecture with high resolution due to subsurface heterogeneity and relatively sparse data from traditional hydrogeological investigations. To overcome difficulties from such sparse data, electrical resistivity tomography (ERT) is introduced to locate DNAPL using time-lapse cross-borehole measurements. Due to the significant impact of geological heterogeneity on DNAPL source zone architecture, a data assimilation framework based on the coupled multiphase fluids-ERT model is developed to jointly invert DNAPL saturation and the permeability field using time-lapse ERT data. To validate the efficiency and performance of this framework, synthetic and laboratory experiments are both performed to monitor DNAPL migration and distribution in 3D heterogeneous sandbox with cross-borehole ERT. Result shows that time-lapse ERT and direct inversion can map the evolution of the DNAPL plume but loses details regarding the plume morphology due to the over-smoothing caused by geophysical inversion using an isotropic and homogeneous roughness-based regularization procedure. By contrast, the coupled inversion is successful to characterize both the permeability field and the evolution of the DNAPL plume with a higher resolution. This is because the coupled inversion is able to directly translate raw geophysical data into hydrologic meaningful information and therefore avoid artifacts caused by direct geophysical inversion.

中文翻译：

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3D 非均质沙箱中 DNAPL 源区结构和渗透场的耦合水文地球物理反演，通过集成卡尔曼滤波同化延时交叉钻孔电阻率数据

摘要 稠密非水相液体 (DNAPL) 分布的表征对于促进修复策略的决策非常重要。然而，由于地下异质性和传统水文地质调查数据相对稀少，以高分辨率表征 DNAPL 源区结构仍然是一个巨大的挑战。为了克服这种稀疏数据带来的困难，引入了电阻率断层扫描 (ERT) 以使用延时交叉钻孔测量来定位 DNAPL。由于地质非均质性对 DNAPL 源区结构的显着影响，开发了基于耦合多相流体-ERT 模型的数据同化框架，以使用延时 ERT 数据联合反演 DNAPL 饱和度和渗透率场。为了验证该框架的效率和性能，我们进行了合成和实验室实验，以监测具有跨钻孔 ERT 的 3D 异构沙箱中的 DNAPL 迁移和分布。结果表明，延时 ERT 和直接反演可以绘制 DNAPL 羽流的演化图，但由于使用各向同性且基于均匀粗糙度的正则化程序地球物理反演引起的过度平滑而丢失了羽流形态的细节。相比之下，耦合反演成功地以更高的分辨率表征渗透场和 DNAPL 羽流的演化。这是因为耦合反演能够将原始地球物理数据直接转化为有意义的水文信息，从而避免直接地球物理反演造成的伪影。进行合成和实验室实验以监测具有跨钻孔 ERT 的 3D 异质沙箱中的 DNAPL 迁移和分布。结果表明，延时 ERT 和直接反演可以绘制 DNAPL 羽流的演化图，但由于使用各向同性和基于均匀粗糙度的正则化程序地球物理反演引起的过度平滑而丢失了羽流形态的细节。相比之下，耦合反演成功地以更高的分辨率表征渗透场和 DNAPL 羽流的演化。这是因为耦合反演能够将原始地球物理数据直接转化为有意义的水文信息，从而避免直接地球物理反演造成的伪影。进行合成和实验室实验以监测具有跨钻孔 ERT 的 3D 异质沙箱中的 DNAPL 迁移和分布。结果表明，延时 ERT 和直接反演可以绘制 DNAPL 羽流的演化图，但由于使用各向同性且基于均匀粗糙度的正则化程序地球物理反演引起的过度平滑而丢失了羽流形态的细节。相比之下，耦合反演成功地以更高的分辨率表征渗透场和 DNAPL 羽流的演化。这是因为耦合反演能够将原始地球物理数据直接转化为有意义的水文信息，从而避免直接地球物理反演造成的伪影。