Nanoparticle tracers are being investigated as a potential tool to measure temperature distributions in geothermal reservoirs. If the temperature distributions could be measured accurately, this would greatly enhance the power and accuracy of thermal breakthrough projection, which could in turn inform reservoir engineering and field management decisions. The design of temperature-sensitive tracers is built around the design of the temperature sensing mechanism. In other words, the mechanism by which temperature is measured and the form and resolution of the resulting data, or response, have a profound impact on how informative that tracer can be about thermal breakthrough. Therefore, it is important to model the responses of candidate tracers in the context of an inverse problem to determine their relative informativeness. We argue that the most informative tracer conceivable is one capable of measuring both the detailed temperature distribution it encountered during its trip through the reservoir and the time at which each temperature was encountered. We define this tracer as a Temperature-Time Tracer (TTT). Modeling was performed to quantify the informativeness of TTTs with respect to thermal breakthrough projection. This hypothetical exercise is useful for establishing a reference tracer to measure each other tracer against. Reservoir simulation and subsequent particle tracking simulation were performed to calculate TTT responses. It was then demonstrated that these responses could be used to infer the topology of the fracture network, including flowrates and travel times. This information was distilled by representing fracture networks as directed graphs. A graph dissimilarity measure called edit distance was used as the objective function in a test inverse problem. We demonstrate that the optimal fracture network model is quite similar to the true fracture network in this test problem in both appearance and thermal breakthrough behavior and that edit distance is well correlated with thermal breakthrough for sufficiently low edit distances.

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