Patent ID: 7983845

Claim:
A method for analyzing a formation, comprising: plotting a plurality of resistivity data points on a resistivity graph of horizontal resistivity with respect to vertical resistivity to obtain a plurality of plotted resistivity data points, the data points obtained by inserting a resistivity measuring instrument into a wellbore drilled through subsurface formations; selecting a first shale point on the resistivity graph based on the plurality of plotted resistivity data points, wherein the first shale point represents a resistivity anisotropy of shale in the formation; generating, for each of a plurality of shale fraction values, a first shale fraction curve on the resistivity graph based on the shale fraction value and the first shale point; generating, for each of a plurality of sand resistivity values, a first sand resistivity curve on the resistivity graph based on the sand resistivity value and the first shale point; and identifying a hydrocarbon yielding region in the formation based on the first sand resistivity curves and the first shale fraction curves.