SUETRI-D Energy Science & Engineering

Triggering mechanisms of induced seismicity and predictive modelling

Investigator: Yuan Tian

To trigger a large earthquake, three key elements are needed: fluid, stimulated fracture and fault. Each element corresponds to a specific process. To activate earthquake on fault, driving force as loading is necessary. In natural earthquakes, the driving force is tectonic plate velocity. In induced seismicity, there are two types of loading sources: fluid pressure from fluid flow, and induced stress field from stimulated fracture. The objective is to investigate how the two loading sources can independently and combine to trigger earthquakes.

Figure 1: triggering mechanisms of induced seismicity

 

(1) Evolution of slip rate and shear stress in earthquake cycles.

Figure 2: spring slider model for seismicity(left), slip rate and shear stress with time under a specified loading rate(right)

(2) The influence of fluid pressure on seismicity depends on several factors: magnitude of pressure, rate with time, spatial gradient and stages of injection process (during injection or shut-in).

Figure 3: fluid pressure acts as loading of induced seismicity
Figure 4: spatial distribution of fluid pressure during injection(left) and shut-in(right)

(3) The influence of induced stress field by stimulated fracture on seismicity depends on type of stimulated fracture and geometry of fractures.

Figure 5: induced stress field by hydraulic open fracture(left) and hydraulic shear fracture(right)

(4) The influence of hydro-mechanical effect in stimulated fracture on seismicity depend on type of stimulated fracture and stages (during injection/shut in).

Figure 6: Relationship between fracture aperture and fluid pressure in two types of stimulated fracture during injection and after shut-in

(5) Investigate influence of injection strategy on seismicity.

Figure 7: proposed injection strategies