Fluid Injection Induced Seismicity in the Oil and Gas Field Areas: Monitoring and Modelling

Past experience has shown that injection-triggered seismicity is an extremely important phenomenon that must be considered when operation oil and gas fields. It is widely accepted that transmission of reservoir pore pressure through the faults, cracks and fractures is the main cause of stress transfer in the rock surrounding the fault zone. As a result, it provides an excessive stress accumulation within the fault zone that may lead to a failure. In order to estimate the excessive shear stress accumulation rate that may trigger the seismic activity according to the rate and state friction model we simulated a stress-strain process in a narrow fault zone between two units during the fluid injection into the one of the units in a simplified 2D model. The simulation is based on the theory of fluid-saturated poroelastic media. We considered the fault zone simulated by relatively higher permeability. The numerical calculations were performed using software libraries with the Freefem++ open code. Injection-triggered seismicity field study was made by the induced seismicity monitoring system in the Northern Sakhalin, Russia. The unusual swarm activity was registered in 2013-2016 in the vicinity of the fluid injection well and is discussed in this study.