[SSS09-P01] Investigation of the physical link between the injection induced seismicity and information from borehole logging
Keywords:induced seismicity, borehole logging, natural fracture
In this study we investigate the natural fracture and in-situ stress data sets from the Basel EGS project in Switzerland. The data originates from the lowermost 2.4 km long borehole section through the basement consisting of granitic to monzonitic rocks. The natural fractures were inferred by careful analysis of acoustic borehole logging images (Ziegler et al. 2015), the in-situ stress data was derived from borehole breakout analysis and some well-test constraint (Valley and Evans, 2009; 2015). Ziegler and Evans, (2020) discovered that the orientation of the seismically inferred faults and natural fractures are similar. Based on these findings of the link between the fault to cause induced seismicity and natural fracture from borehole logging, we investigate the physical link between those beyond the geometrical consistency. We estimated various geomechanical parameters such as shear stress, normal stress, apparent shear strength, i.e., critical pore pressure, and slip tendency. We compared the distributions of those parameters estimated from induced seismicity and natural fractures. We try to find the link between those relationships and discuss the preliminary foundings. Then, we will extend our findings to the theory proposed by the conceptual theory of b-value reduction with increasing stress (Scholtz, 1968).