INJECTION INTO GEOTHERMAL SYSTEMS

Abstract

We present the results of a suite of experiments which have been performed in order to determine the effects of injection into geothermal reservoirs. The results obtained from the experiments are compared with theoretical predictions of the evolution of temperature profiles witin a geothermal reservoir following the injection of supercooled liquid. For the case of constant rate liquid injection in an axisymmetric geometry into a liquid-filled porous medium, we find that at slow rates of injection heat is conducted from the far-field towards the source. However, at higher rates of injection, an isothermal zone develops close to the injection well.

We then present the results of an experiment in which liquid was injected into a porous slab initially filled with superheated vapour. We compare the evolution of the temperature profile within the system with the theoretical prediction (Woods and Fitzgerald, 1997) and find that a sharp interface may develop between the liquid- and vapour-filled regions.

Finally, we investigate the injection of liquid into a fracture which initially contains superheated vapour. We compare the evolution of the temperature profile within the fracture with a numerical prediction obtained from TOUGH2 (Pruess, 1991). It is found that a broad two-phase region exists between the completely liquid-filled and vapour-filled zones of the system.