This project has two primary goals. The first is to advance the conceptual design of a new generation of deep-sensing borehole electromagnetic (EM) and seismic instruments that can provide 3-D images of reservoir flow units and of their petrophysical properties to distances of tens of meters from the wellbore. The second involves the development of efficient numerical algorithms and computer codes for the joint inversion of borehole seismic and EM measurements. These algorithms will integrate data governed by multi-phase fluid flow, visco-elastic, and electric phenomena into consistent 3-D images of lithology, porosity, permeability, and fluid saturation. Use of borehole seismic measurements in addition to EM measurements will reduce non-uniqueness and hence will improve the accuracy of the estimated petrophysical parameters. Deterministic and stochastic inversion techniques will be used to estimate reservoir-scale distributions of petrophysical properties.