Method for evaluating formation density using a source,two spaced-apart gammaray detectors and a stand-off measurement tool in a borehole,and a model

摘要

A logging-while-drilling density sensor includes a gamma ray source and at least two Nal detectors spaced apart from the source for determining measurements indicative of the formation density. An analytic function based on a heuristic model is used to predict the measured response as a function of offset, mud density and formation density. The model may be used to provide a caliper measurement where acoustic caliper data are unreliable.