- Synthetic microseismic events are formed in the model by new micro-crack (tensile bond breaks) and slip on existing joints (assuming all slips are seismic)
- Event magnitudes associated with micro-cracks and joint slips are calculated differently
- Since springs are brittle and their breakage always results in local instability, it is possible to estimate radiated seismic energy based on transient change in strain energy in the vicinity of the broken spring or micro-crack
- In the case of slippage across natural fractures, the energy released by the slip events is calculated based on the slip area, slip magnitude, and elastic properties of the surrounding medium
- This allows ranking of different microseismic events (both bond breakage and joint slips) occurring during simulation based on their magnitude
- Events that are related spatially and temporally are clustered together
The figure below is an XSite model of a multi-stage horizontal completion with five regularly spaced injection ports (plan view). A set of generic rock properties was used with an existing fracture network (not shown) orientated at 60° to σHmax for illustration. Acoustic emissions are shown colored by magnitude associated with micro-cracks (left) and with slip along existing joints (right).