In parallel of in-situ test of colder reinjection with the test heat exchanger, a numerical model of this reinjection is mandatory to assess its effect on short and long terms powerplant operation. A possible impact would be a decrease of production temperature due to hydraulic connection already existing between the different wells.
To achieve this goal, a 3D structural model of Soultz reservoir has been created based on existing available model and data (Sausse et al. ,2010). The data have been gathered from geological studies, well logs, vertical seismic profiles and induced micro-seismicity clouds. About 50 fractures in the granite have been considered during this structural compilation. Among them, 5 have been kept in the hydrothermal model based on various criteria such as flow anomalies, temperature anomalies, mud losses, seismic cloud, tracer tests results, fracture extension and wether they connect or not wells with each other.
The hydrothermal model has been calibrated with power plant operation data to ensure that it reproduces well pressures and temperature evolution observed over more than 3 years of operation. First results when simulating the colder reinjection (decrease of reinjection temperature from 70°C to 50°C) shows that the production temperature is quickly affected by a few degrees. Then, the temperature remains almost stable for decades. This is in line with current knowledge on this reservoir which highlights some connection between wells and some more far field contribution to the producer. A sensitivity analysis is in progress to assess the robustness of this model, help improving the history matching and the reproducibility of these first results.
These first results have been presented at European Geothermal Workshop in October 2019.
Revisited Soultz-sous-Forêts structural model
Slice across the hydrothermal model after 30 years of colder reinjection (lines are representing well paths, dashed if projected on the slice)
Sausse J., Dezayes C., Dorbath L., Genter A., Place J., 2010. 3D model of fracture zones at Soultz-sous-Forêts based on geological data, image logs, induced microseismicity and vertical seismic profiles. C. R. Geoscience 342, 531-545, https://doi.org/10.1016/j.crte.2010.01.011