| Title | Controlled Column Experiments to Determine the Theory and Sensitivity of thermo-sensitive Tracers |
|---|---|
| Authors | Friedrich MAIER, Adriatik OLLONI, Tobias LICHA |
| Year | 2013 |
| Conference | Stanford Geothermal Workshop |
| Keywords | thermo-sensitive tracer, column experiment, isothermal system, theory testing, temperature estimation |
| Abstract | The reinjection of abstracted thermal water is a common procedure in geothermal reservoir management. It provides several advantages e.g. disposal of geothermal wastewater, the maintenance of the reservoir strain and the reduction of the subsidence due to compaction. On the other hand, due to this practice the reservoir cools down since the extracted energy may exceed the natural heat flow. This limits the life time of a geothermal system. For an optimal reservoir management during geothermal power plant operation it is essential to locate and describe the thermal front in the subsurface. Currently, there is no method available for measuring this thermal drawdown. One promising tool to overcome this shortage is the application of thermo-sensitive tracers. Unfortunately, earlier reported field experiments failed due to inappropriate tracer compounds. Recently, new compounds were synthesized in our group with fluorescent properties allowing in-situ measurement of tracer breakthrough curves. These tracers have well known kinetic parameters, which is a prerequisite in tracking thermal fronts. According to the obtained pre-exponential factor A and the activation energy Ea of the Arrhenius law these thermo-sensitive tracers may already be used in short-term experiments (e.g. PushPull) or low temperature reservoirs (T < 100 °C). This circumstance gave us the opportunity to conduct controlled laboratory experiments with focus on tracer breakthrough curve correlation to reservoir temperature. The experimental setup consists of two consecutively connected columns, where each is heated to a certain temperature using a rapid flow water bath. Preliminary results, with sieved sand as a packing material, show a precise estimate of the applied temperature from the recorded tracer breakthrough curve. It is the first time that reliable experiments were performed to evaluate the underlying theory. |