Thermo-hydro-mechanical processes in deep crystalline rock – Experiments and numerical modelling
Projektleitung: O. Kolditz, M. Sauter
Mitarbeiter Prof. Dr. M. Sauter, Dr. M. Lodemann, Dr. J. Ghergut, Dr. T. Licha
Partner: C.I. McDermott, O. Kolditz (Univ. Tübingen), M. Herfort (ETH Zürich), H. Tenzer (Urach), H. Behrens (München), P. Rose (EGI Utah)
Förderer: DFG (Sa 501/16-1,2,3,4,5)
Zusammenfassung: The KTB field laboratory (German part of the International Continental Drilling Programme, ‘ICDP’) provides a unique opportunity to analyse coupled thermo-hydro-mechanical behaviour by combining modelling and experimental data. During previous phases of the project (2003-2004), emphasis was placed on reproducing the geometry of the reservoir, including the most important fracture zones, the construction of a hydraulic model, accounting for non-linear fracture hydraulics, the consideration of poro-elastic effects during large-scale pumping tests and the introduction of thermo-elastic effects (Tuebingen team). Furthermore, a method for efficiently predicting solute and heat transport in hybrid, fractured-porous media at different time scales has been developed (Goettingen team). The experiments comprised special tracer techniques in order to characterize the contact surface between fracture network and rock matrix (Goettingen team).
The figure shows an example of tracer breakthrough curves, as gained from the dual-tracer push-pull test first carried out at the pilot KTB hole. Unlike in flow path tracings, tracer ‘arrival’ times from a push-pull test are not primarily related to a residence time distribution in the investigated system, but to the depth of borehole-fracture intersections. The mid-late slopes of tracer BTCs can be interpreted with the diffusion and sorption properties of the tracers. Without an accurate knowledge of tracer properties, however, the targeted system properties (like fracture surface areas) cannot be unambiguously extracted from the tracer BTCs. Since relatively little is known about tracer behaviour in a geothermal environment, a new experimental focus of this phase of the project will be the laboratory simulation of in-situ physicochemical and mineralogical conditions of the reservoir, for ascertaining the thermostability and interaction properties of the tracers used in the field experiments.
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