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Tracer Testing in Propped EGS Fractures: Modeling and Analysis
Sarah SAUSAN, Roland HORNE
[Stanford University, USA]
This paper details the modeling and analysis tracer testing in propped EGS fractures using Utah FORGE tracer data. Two types of tracer tests were conducted at Utah FORGE: stim tracer testing, performed during stimulation with stage-unique tracers mixed with proppant, and flowthrough tracer testing deployed during crossflow and circulation tests. Stim tracer results obtained in 2024, deployed using different compositions (nano- versus chemical tracers) and methodologies, were compared to inform the stim tracer deployment strategy in propped EGS fields. Additionally, a methodology for modeling multicomponent flowthrough tracers in EGS wells is being developed. The stim tracer analysis encompasses various deployment and sampling strategies, including the use of chemical versus nanotracers, different sampling durations, and sampling frequencies. Stim tracer results were analyzed for concentration trends, flow contributions, and tracer recovery returns. Our analysis affirms that simultaneously deploying both nano- and chemical stim tracers helped compare their behavior and effectiveness, as well as establishing a baseline for subsequent analyses. Given that the nanotracer dataset has consistently shown more erratic patterns than chemical tracers, it is recommended to supplement nanotracer stimulation with chemical tracers as a control. Additionally, extending the sampling duration to at least 7 days, ideally longer, would allow capturing the full trend of tracer recovery. The multicomponent tracer model employs tracer dispersion as the governing equation and least-squares fitting with a soft flow-fraction penalty as the objective function. Synthetic datasets were generated to aid in model development. This initial attempt at multicomponent tracer modeling in EGS wells demonstrated promising results, especially when involving a few components. Improvements to the modeling techniques will be explored to enable the model to better handle a larger number of components.
Topic: Tracers