Modelling of Rock-Water Thermal Interaction in Different Scales

Abstract

We study two analogous configurations of water flow in fractures in granite, with heat exchange between water and surrounding rock. The first case is a laboratory experiment on compact granite block 800x600x300 mm with one artificial fracture oriented in the largest plane. The experiment was part of a project of underground heat storage research, as a preparation for in-situ test evaluation. The experiment is configured so that hot water is injected by a borehole into the fracture and leaves the block along one edge of the fracture. Temperature is measured in the fracture, inside rock and on the surface in several points. The second case is a tunnel water inflow observation. The temperature in the tunnel changes quasi-periodicaly in the annual cycle by artificial operation of transport pipe, while the surrounding rock of stable temperature in more than 50m depth is disturbed by these changes. This causes thermal non-equilibrium between the blocks of compact rock and water in the fractures. We show that both configurations can be described by the same conceptual model, with different problem size and input data. Simulations are done in the FEFLOW software. We can also partly interpret how the flow is distributed in the fracture plane or if it is present in a wider structure of crushed rock. The work has been supported by the Ministry of Industry and Trade of the Czech Republic, project code FR-TI 3/325.