Characterisation of the Basel 1 enhanced geothermal system

This paper describes the steps that have been undertaken to create an enhanced geothermal system (EGS) at the Deep Heat Mining Project in Basel, Switzerland. Preliminary results from drilling, logging, hydraulic testing and stimulating the Basel 1 well are summarized. The project was suspended following the occurrence of several 'felt' microseismic events. Because such events may be an inherent risk with current methods of reservoir stimulation, the paper analyses the possible mechanisms of hydraulically induced shearing processes and suggests methods by which the risk may be reduced. The observations are integrated into a model of the geothermal reservoir where aspects of both the reservoir development and the driving mechanism for the perceptible induced seismic events are considered. (C) 2008 Elsevier Ltd. All rights reserved.