Page 301 - Geothermal Energy Systems Exploration, Development, and Utilization

5.6 Bad Urach 277
Top view, no coupling
200

0 East−west scale (m)

−200
Top view, fully coupled processes
200

0 East−west scale (m)

Development of preferential folow paths Cross section, fully coupled processes −200

3800

4000 Depth (m)

4200
−400 −200 0 200 400
North south scale (m)

50 106 162
Temperature (°C)
Figure 5.22 Development of preferential flow paths as a
result of positive feedback between the coupled processes.

heterogeneities during the heat extraction. Figure 5.21 illustrates the difference in
the reservoir temperature between a noncoupled constant parameter scenario HT
and the coupled hydraulic mechanical HT (MHC) scenario after about 11 years.
The larger differences are shown in dark. Here flow and therefore cooling is being
concentrated in the upper part of the reservoir, and preferential flow paths start
to develop. Figure 5.22 illustrates the same scenario with coupling to the thermal
stress, and this leads to the development of preferential flow paths becoming much
more significant. In this figure after seven years, the thermal coupling has not only
led to a significantly higher flow rate in the system, but also to the development of
preferential flow paths. These preferential flow paths represent potential short cuts
in the operation of the reservoir.