CORRECTING SHALE VOLUME AND MEASURING ANISOTROPY IN INVADED ZONE

This disclosure describes a method, apparatus, and non-transitory computer-readable medium product for correcting a shale volume estimated from gamma ray information using a continuous radial profile of horizontal resistivity in the invaded zone and a continuous profile of anisotropy. The continuous radial profile of horizontal resistivity may be estimated by modeling a hydrodynamic evolution of the invaded zone (a) a step-wise radial profile of horizontal resistivity in the invaded zone as an initial estimate of horizontal resistivity in the invaded zone; (b) an estimated shallow resistivity at a borehole wall; and (c) an estimated horizontal conductance of the formation at an outer boundary of the borehole wall estimated from multi-component induction logging information. The shale volume may be corrected if at least one of (a) an estimated horizontal resistivity of the borehole wall and (b) an estimated horizontal resistivity of the earth formation is not between about a minimum horizontal resistivity and about a maximum horizontal resistivity estimated using the anisotropy.