Induced microseismic events

Moriya, H., Nakazato, K., Evans, K. F., Niitsuma, H., Jones, R.H. and Baria, R. (2001). Evaluation of the Soultz HDR system by precise mapping techniques of induced microseismic event. Trans. Geothermal Resources Council 2000, Vol. 25, 187-190. 

The multiplet-clustering analysis is a method to estimate relative positions of the multiplet clusters as well as the relative source locations within individual multiplets (Moriya et al., 2CK)3). We have applied the multiplet-clustering analysis to the induced microseismic events as following procedures. 

Figure 2. Source locations of induced microseismic events, where the events...

It is considered that some fractures opened with increasing pore-pressure maybe after shear slip because the maximum wellhead pressure is about lOMPa. However, Mode I fractures can not radiate seismic events having enough energy, and we can not detect these seismic events. Therefore, we consider only shearing fractures for estimation of critical pore-pressure using induced microseismic events. 

Through observation of induced microseismic events and examination of well logging data, it has been understood that the permeable zone seems to be created by migration of shearing joints during hydraulic fracturing test, and that microseismic multiplets is considered to be seismic events associated with shearing of fractures which are favourably oriented to stress field. 

Feignier B, Young RP (1992) Moment tensor inversion of induced microseismic events Evidence of nonshear failures in the < M < -2 moment magnitude range, Geophys. Res. Lett. 19 1503-1506... 

In this paper, we suggest a method for estimation of pore-pressure during hydraulic stimulation of geothermal reservoir by using the induced microseismic multiplets. The results of the application to the microseismic events at Soultz field are demonstrated showing the feasibility of the method. 

Evans, K. F., Jones, R., Soma, N. and Baria, R. (1999). Correlation of near-borehole microseismic structures defined by the collapsed cloud of events induced by the 1993 GPKl stimulation with flowing fractures.. Internal Report of MURPHY Project 1999, NEDO. 

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