Patent ID: 7596452

Claim:
A method of evaluating an earth formation, the method comprising: irradiating the earth formation with a source of radiation on a tool within a borehole; making measurements at least two spaced apart detectors responsive to gamma rays resulting from the irradiating; defining a heuristic model that includes three density parameters: (I) a formation density, (II) a standoff of the tool, and (III) a density of a mud in the borehole, the model further comprising a first path length from the source of radiation to a first one of the at least two spaced apart detectors and a second path length from the source of radiation to a second one of the at least two spaced apart detectors; using the measurements and the heuristic model to estimate values of two of the three density parameters corresponding to a specific value of the third of the three density parameters; and recording the estimated values of the two of the three density parameters on a suitable medium.