资源环境科技发展态势分析平台

The Barnett Shale in Texas experienced an increase in seismicity since 2008, coinciding with high-volume deep fluid injection. Despite the spatial proximity, the lack of a first-order correlation between seismic records and the total volume of injected fluid requires more comprehensive geomechanical analysis, which accounts for local hydrogeology. Using time-varying injections at 96 wells and employing a coupled linear poroelastic model, we simulate the spatiotemporal evolution of pore pressure and poroelastic stresses during 2007-2015. The overall contribution of poroelastic stresses to Coulomb failure stress change is similar to 10% of that of pore pressure; however, both can explain the spatiotemporal distribution of earthquakes. We use a seismicity rate model to calculate earthquake magnitude exceedance probability due to stress changes. The obtained time-dependent seismic hazard is heterogeneous in space and time. Decreasing injection rates does not necessarily reduce probabilities immediately.

Plain Language Summary It is believed by scientific communities that disposing of wastewater into deep rock formations may induce earthquakes. However, it has been debated how and when injection operations affect the seismic hazard in a region. Here we investigate how crustal stress changes as fluid seeps into rocks using computer simulations and then implement numerical models linking the evolution of stress to the elevated seismicity on nearby faults. A combination of these computer models with the rule of statistics enables us to constrain temporally variable seismic hazard in a region. Considering Barnett Shale, Texas, a site of intense injection operation between 2007 and 2015, we show that elevated seismic hazard is highly variable in time and space as a result of widespread high-volume, time-varying fluid injection. In contrast to some opinions, decreasing injection volume does not necessarily reduce earthquake probability. Our model and results advance the understanding of hazards associated with induced seismicity in Texas and elsewhere. It can also benefit the communities working on earthquake hazard forecasting.