Microseismicity of Non-linear Fluid-rock Interactions - From Geothermic Stimulations to Fracturing of Barnett Shales

Borehole stimulations by fluid injections are common for developments of hydrocarbon and geothermic reservoirs. Often they induce numerous microearthquakes. Spatio-temporal dynamics of such induced microseismic clouds can be used to characterise reservoirs. However, a fluid-induced seismicity can be caused by a wide range of processes. We propose an approach to describing a broad range of non-linear fluid-rock interactions. We show that a linear pore pressure relaxation and a hydraulic fracturing are two asymptotic end members of a set of non-linear diffusional phenomena responsible for seismicity triggering. Microseismicity of Barnett Shales shows signatures of a non-linear diffusional triggering with an extremely strong hydraulic permeability enhancement in a 3-D domain of the reservoir. This indicates a process of a volumetric hydraulic fracturing via reopening of compliant preexisting fractures.