ABSTRACT
Hydraulic fracturing technology is essential for the development of Enhanced Geothermal Systems (EGS) to increase the permeability of tight rock formations and hence the energy recovery from a petro geothermal reservoir. However, fracturing and the subsequent increase in energy production may pose the risk of induced seismicity. Previous studies established the mechanisms of microseismic events during hydraulic fracturing in the Deep Heat Mining project Basel using the numerical simulator FLAC3Dplus. In this paper, an innovative injection strategy using a linear increasing injection rate to reduce the maximum magnitude of microseismic events Mmax has been proposed. In addition, the new EGS-strategy allows a combination of both the linear increased injection rate and the multiple fracture system to be studied numerically. Results show that the risk of induced seismicity can be considerably minimized by the proposed strategy. The simulation shows that increasing the number of fractures in the tight reservoir decreases Mmax significantly. It is recommendable that multiple hydraulic fracturing technology be applied in the development of enhanced geothermal systems not only to minimize the risk of induced seismicity but also to increase the surface area for heat exchange and recovery efficiency.
