Reservoir Characterization Based Upon the Onset of Time-Lapse Changes

Abstract:

Time-lapse geophysical monitoring has significant potential as a tool for reservoir characterization, that is for determining reservoir properties such as permeability. Onset times, the calendar time at which geophysical observations begin to deviate from their initial or background values, provide a useful basis for such characterization. We find that, in contrast to time-lapse amplitude changes, onset times are not sensitive to the exact method used to related changes in fluid saturation to changes in seismic velocities. As a consequence of this, we find that an inversion for effective permeability based upon onset times is robust with respect to variations in the rock physics model. Furthermore, synthetic tests indicate that onset times can be obtained from noisy seismic amplitudes. Testing also indicates that large-scale effective permeability variations can be recovered even if we use onset times
from seismic surveys that are spaced as much as 300 days apart.