Phase-shift measurement analyses of time-lapse multicomponent seismic data over a multi-well hydraulic stimulation, Wattenberg Field, Denver Basin

Instantaneous phase calculations estimate phase differences in multicomponent seismic data between traces acquired pre- and post-stimulation of eleven horizontal wells in Wattenberg Field, Denver Basin. Estimated phase shifts illustrate the ability of multicomponent seismic to image the reservoir response associated with the interaction of stimulated, hydraulic fractures with natural fractures. Time-lapse shear-mode seismic showed the largest response with maximum phase differences of about 30 degrees. Converted-mode seismic provided shifts of about 20 degrees, and compressional-mode seismic gave shifts of about 15 degrees.;Instantaneous phase calculated for the crosscorrelation function of time-lapse traces windowed at the base of the reservoir provided the largest phase differences. Traveltime and phase differences both show that the western half of the reservoir where wells are more closely spaced responded more strongly to stimulation than the eastern half. Interpretation of simple 1D modeling, hydrocarbon production data, chemical tracer analysis, formation image logs, microseismic, and other seismic analysis suggests that measured phase differences correlate to regions of the reservoir where more fractures were opened during stimulation.;Phase shifts may measure attenuation and interference that results from the effects of hydraulic stimulation on propagating seismic energy and not just time or velocity like other measures. In unconventional reservoirs attenuation and interference may be more important mechanisms for change than velocity. Phase shifts measured in multicomponent seismic can provide relative information about fracture aperture, size, and orientation, and permanent reservoir monitoring could capture the dynamic response of reservoirs to widespread hydraulic stimulation as across Wattenberg Field. Multicomponent time-lapse monitoring, especially with phase-shift measurements, provides critical reservoir information unavailable through single mode seismic analysis or microseismic monitoring.