Estimating the crust permeability from fluid-injection-induced seismic emission at the KTB site

Abstract

During the hydraulic-fracturing experiment in the German Continental Deep Drilling Borehole (KTB) in December 1994, microseismic activity was induced. Here we develop a technique for estimating permeability using the spatio-temporal distribution of the fluid-injection-induced seismic emission. The values we have obtained for the KTB experiment (0.25 × 10−16 to 1.0 × 10−16 1.0 × 10−16 m2) are in a very good agreement with the previous hydraulic-type permeability estimates from KTB deep-observatory studies. In addition, our estimates of the hydraulic diffusivity support the previously calculated value for the upper crust, which is of the order of 1 m2 s-1. However, this estimate now relates to the depth range 7.5–9 km.