资源环境科技发展态势分析平台

In the summer of 2015, a series of thermal tracer tests were conducted at the Widen field site in northeast Switzerland to validate travel time-based thermal tracer tomography for reconstruction of aquifer heterogeneity. Repeated thermal tracer tests and distributed temperature observations were used to obtain a multisource/multireceiver tomographic experimental setup. After creating forced hydraulic gradient conditions, heated water was injected as a pulse temperature signal via a double-packer system. With this solution, long temperature recovery periods were not required between the repeated injections at the expense of smaller observed temperatures. The recorded temperature breakthrough curves delivered a tomographic travel time data set that was inverted assuming advection-dominated condition. The obtained hydraulic conductivity tomogram for a small aquifer profile is validated with the results of the findings from previous field investigations at the same site. The reconstructed profile confirms the presence of a thin sand layer with low permeability and reveals a previously unknown low-permeable zone close to the bottom of the aquifer. The inverted hydraulic conductivity values also correspond with those from previous tracer tests. Thus, the results of this study demonstrate the potential of thermal tracer tomography for resolving structures and transport characteristics of heterogeneous aquifers.