Method for through-casing 3-phase saturation determination

An apparatus for estimating a parameter of interest of an earth formation, the apparatus comprising:

• a carrier configured to be conveyed through a borehole penetrating the earth formation;
• a neutron source disposed at the carrier and configured to irradiate the earth formation;
• at least one detector configured to measure radiation emitted from the earth formation resulting from the irradiating;
• and
• a processor configured to:
• calculate or determine a mathematical parameter from radiation measured by the at least one detector;
• predict values of the mathematical parameter over a range of values of an earth formation property;
• and
• compare the mathematical parameter to the predicted values to estimate the parameter of interest.

A non-transitory machine-readable storage medium for use with an apparatus for estimating a parameter of interest of an earth formation, the apparatus comprising:

• a source of radiation configured to be conveyed in a borehole penetrating the earth formation and to irradiate the earth formation;
• and
• at least one detector configured to produce signals indicative of results of interactions of the radiation with nuclei of the earth formation;
• the medium comprising instructions, which enable a processor to:
• calculate or determine a mathematical parameter from radiation measured by the at least one detector;
• predict values of the mathematical parameter over a range of values of an earth formation property;
• and
• compare the mathematical parameter to the predicted values to estimate the parameter of interest.