Mapping of propagating pressure in reservoir from the data of microseismic events in the 1993 hydraulic stimulation at the soultz HDR site

In the hydraulic stimulation, massive fluid is injected into subsurface rock through drilled wells. Then a number of microseismic events are commonly observed. By analyzing those data of microseismic events, we can estimate the orientation, i.e. dip and strike, of the fracture which slides to induce microseismic event. From the estimated fracture orientation, taking into account the in situ stresses and the Mohr-coulomb criterion to describe the critical condition of fracture sliding, we can estimate the pore pressure at the location of sliding fracture and at the time when the sliding occurs, in other words, when the microseismic event occurs. The estimated values of pore pressure are sorted in a certain manner for each equally divided spatial region, i.e. block, to give spatial distribution of pore pressure and its variation with time during hydraulic stimulation. We applied this method to the microseismic data observed during the hydraulic stimulation performed in September 1993 at the Soultz HDR site in France, and succeeded in showing the pressure propagation through the rock formation during the test.