In engineered geothermal systems, the spatial heterogeneity in fracture aperture plays an important role in flow pattern evolution, which significantly affects the reservoir performance. The initial flow field in a fracture is mainly determined by the aperture spatial distribution, and the pattern of the channeled flow tends to evolve due to the uneven temperature decrease during heat production. In geothermal reservoir either dominated by a single fracture or a fracture network, it is essential to understand the thermal drawdown-induced flow channeling in a single fracture with spatially heterogeneous aperture. In this study, we investigate the effects of aperture heterogeneity on flow pattern evolution in a single-fracture system. We especially focus on how the autocorrelation characteristics of the aperture field affect the reservoir production life, integrated production temperature, and average pressure loss. We use a discrete fracture network (DFN) -based numerical model to simulate the coupled thermal-hydrological-mechanical (THM) processes in a penny-shaped fracture intersecting with an injection well and a production well. Correlation length, ranging from 25 m to 150 m, is the primary independent variable under investigation, and a large number of realizations were performed to ensure the aperture spatial distributions are properly represented. We found that the correlation length does not affect the expectation of reservoir performance, while greater correlation lengths tends to increase the performance uncertainty. We also found that although the initial preferential path(s) always tend to carry a greater portion of flow over time, one or multiple preferential paths that deviate from the shortest line between the two wells can effectively improve the reservoir performance. AUSPICES: This work was performed under the auspices of the U.S. Department of Energy by Lawrence Livermore National Laboratory under Contract DE-AC52-07NA27344. Abstract release number: LLNL-ABS-661685.

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