Publication Date:
2020-05-14
Description:
Many geo-engineering applications, such as unconventional hydrocarbon production, geothermal energy exploitation, or wastewater disposal, require fluid to be injected into the subsurface, and often induces earthquakes. The magnitudes of these fluid-injection induced earthquakes are relatively low – usually M 〈 5 – compared to natural tectonic earthquakes. However, the hypocenters of these earthquakes locate at shallow depth, and therefore the impacts to the surface structures are not negligible. It became important to understand the physical mechanisms of the fluid injection induced earthquakes, and to develop a reliable numerical simulation tools that can capture the relevant physics and be applied in real engineering applications. In this Chapter, we present numerical simulation of fluid injection in a fractured rock mass using the hydro-mechanically coupled PFC2D modelling. We present two different modelling cases and investigate spatial and temporal evolution of the seismic events induced by fluid injection in a fractured rock mass subjected to an anisotropic stress field. From the modelling of hydraulic stimulation of a fractured rock mass, the results show that the magnitudes of the seismic events generated under a higher stress magnitude and a higher level of stress anisotropy condition are of larger magnitude, and therefore the b-values from the magnitude-frequency distribution is lower. From the modelling of fluid injection near to a fault zone, the results confirm that the magnitudes associated with fault slip tend to be larger in case when the fault zone acts like a fluid flow barrier by generation of large overpressure zone. The obtained results from the two modelling cases are consistent with the laboratory findings and show similarities to the observations in the fields.
Language:
English
Type:
info:eu-repo/semantics/bookPart
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