Characterization of hydraulic properties of rocks using probability of fluid-induced microearthquakes

Abstract

The use of borehole fluid injections is typical for exploration and development of hydrocarbon or geothermal reservoirs. Such injections often induce small-magnitude earthquakes. The nature of processes leading to triggering of such microseismicity is still not completely understood. Here, we consider induced microseismicity, using as examples two case studies of geothermal reservoirs in crystalline rocks and one case study of a tight-gas sandstone reservoir. In all three cases, we found that the probability of induced earthquakes occurring is very well described by the relaxation law of pressure perturbation in fluids filling the pore space in rocks. This strongly supports the hypothesis of seismicity triggered by pore pressure. Moreover, this opens additional possibilities of using passive seismic monitoring to characterize hydraulic properties of rocks on the reservoir scale with high precision.

Bayesian inversion of pressure diffusivity from microseismicity

“…This theory predicts that the first event time t for microseismic events occurring a distance r from the injection well will lie on the level sets of r 2 ∕t. They demonstrate that this prediction is born out in the field for microseismic observations in crystalline rock for geothermal stimulation (Shapiro et al, 2002(Shapiro et al, , 2005a(Shapiro et al, , 2005b and in virtually impermeable shales for unconventional hydrocarbon stimulation (Hummel and Shapiro, 2013). This theory may be extended to predict not only the microseismic triggering fronts (the first events at a given distance), but also the statistics of events that occur after this front, including predictions of moment magnitude.…”

“…Shapiro and his collaborators (Shapiro et al, 2002(Shapiro et al, , 2005a(Shapiro et al, , 2005b) propose a physical model that directly ties fluid flow during injection with observed microseismic data. Theirs is a simple physical model that is based on the concept of linking the increasing pore pressure from fluid injection to the triggering of microseismic events using the Mohr-Coulomb theory of rock fracturing.…”

Slip synergism of planar strike-slip fault during meta-instable state: Experimental research based on digital image correlation analysis

“…For evaluating hydraulic diffusivity (D) of the crust, the method developed by Shapiro to describe pore-pressure perturbations caused by fluid injections into a borehole was used [Parotidis et al, 2003[Parotidis et al, , 2004Shapiro et al, 1997Shapiro et al, , 2002Shapiro et al, , 2005Shapiro et al, , 2006. In the isotropic medium, the pore pressure diffusion can be described as Biot's equation, the equation has the form…”

Controls on earthquake rupture and triggering mechanisms in subduction zones

“…Swarms are common in volcanic regions and have been explained as resulting from the stress perturbations during magma intrusions (e.g., Einarsson and Brandsdóttir, 1980;Smith et al, 2004) as well as from the movements of volatiles such as CO 2 (e.g., Prejean et al, 2003;. Similarly, earthquake swarms are common in regions of aqueous fluid flow such as geothermal areas and during hydrofracture experiments (Audigane et al, 2002;Shapiro et al, 2005;Bourouis and Bernard, 2007). Thus, a clear intuition has developed that swarms are driven by aseismic events that temporarily modify the stress state within the crust.…”