Consistency of stress state,locations and source mechanisms of events induced by hydraulic fracturing: downhole monitoring |
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| Authors: | Zuzana Jechumtálová Fangdong Chu Gang Yu Jan Procházka |
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| Affiliation: | 1. Seismik s.r.o., Kubi?ova 1265, 182 00 Prague 8, Czech Republic;2. Institute of Geophysics, v.v.i., Academy of Sciences of the Czech Republic, Bo?ní II 1401, 141 31 Prague 4, Czech Republic;3. BGP Inc., China National Petroleum Corporation, Fanyang W Rd 18a, 072 750 Zhuozhou City, Hebei, P.R.China |
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| Abstract: | We present results of processed microseismic events induced by hydraulic fracturing and detected using dual downhole monitoring arrays. The results provide valuable insight into hydraulic fracturing. For our study, we detected and located microseismic events and determined their magnitudes, source mechanisms and inverted stress field orientation. Event locations formed a distinct linear trend above the stimulated intervals. Source mechanisms were only computed for high‐quality events detected on a sufficient number of receivers. All the detected source mechanisms were dip‐slip mechanisms with steep and nearly horizontal nodal planes. The source mechanisms represented shear events and the non‐double‐couple components were very small. Such small, non‐double‐couple components are consistent with a noise level in the data and velocity model uncertainties. Strikes of inverted mechanisms corresponding to the nearly vertical fault plane are (within the error of measurements) identical with the strike of the location trend. Ambient principal stress directions were inverted from the source mechanisms. The least principal stress, σ3, was determined perpendicular to the strike of the trend of the locations, indicating that the hydraulic fracture propagated in the direction of maximum horizontal stress. Our analysis indicated that the source mechanisms observed using downhole instruments are consistent with the source mechanisms observed in microseismic monitoring arrays in other locations. Furthermore, the orientation of the inverted principal components of the ambient stress field is in agreement with the orientation of the known regional stress, implying that microseismic events induced by hydraulic fracturing are controlled by the regional stress field. |
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| Keywords: | Monitoring Data processing Inversion |
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