BACKGROUND

For oil and gas exploration and production, a network of wells, installations and other conduits may be established by connecting sections of metal pipe together. For example, a well installation may be completed, in part, by lowering multiple sections of metal pipe (i.e., a casing string) into a wellbore, and cementing the casing string in place. In some well installations, multiple casing strings are employed (e.g., a concentric multi-string arrangement) to allow for different operations related to well completion, production, or enhanced oil recovery (EOR) options.

During the lifetime of the well the integrity of the cement, casing string, production tubing, and formation may be examined through one or more measurements. These measurements may be performed by a nuclear density tool. Existing nuclear density tools measure a bulk density of a single layer averaged over the depth of investigation, providing little information as to the variation in density as a function of radial distance from the sensor. Current density tools use the contrast between a near and far detector to apply a borehole correction to the density measured by the far detector. Usually the correction requires knowledge of the borehole environment, such as borehole size, standoff, and borehole fluid composition and density. Additionally, existing nuclear density tools and calculation algorithms are designed to extract only a bulk density of the surrounding material averaging over the sampling range/thickness, therefore, lacking the ability to resolve any intrinsic differences in individual annular layers within that volume.

