Reservoir Average Permeability from Seismic and Log Data

Abstract

The objective is to demonstrate the possibility of reservoir permeability mapping using a frequency-dependent seismic attribute and analysis of log data. The coefficients of normal reflection and transmission of a planar p-wave from a permeable boundary can be expressed asymptotically as power series with respect to a small dimensionless parameter depending on the reservoir fluid mobility. The zero-order terms of the asymptotic expressions do not depend on reservoir rock permeability and are similar to the one predicted by the classical elastic model. The next, first order, term involves a factor proportional to fluid mobility, both for reflection and transmission coefficients. In case of a very thing porous permeable layer (h<<λ) transmitted-reflected slow waves can create a low frequency resonance providing an opportunity for seismic inversion. The functional structure of the first order asymptotic term suggests a frequency-dependent seismic attribute, which is proportional to reservoir fluid mobility. We have derived such attribute from real seismic data and analyzed it vs. log data. We have obtained that the possibility for seismic imaging of the reservoir transport properties, in particular mapping the lateral permeability variations, is realistic.