A dual-spacing formation [[density log]]. The compensated [[formation]] density logging device employs two [[detector|detectors]] spaced at different distances from the [[source]]. The detector at the shorter spacing is particularly sensitive to the [[density]] of material immediately adjacent to the face of the [[pad]]. The contribution of this material, which includes [[mud cake]] and drilling [[mud]] filling minor [[borehole]] wall irregularities, affects the response of each detector to a different degree. The measurements from both detectors provide a means for making a correction for the influence of drilling mud and mud cake on the measurements. This correction is automatically added to the uncompensated density measurement from the detector at the longer spacing. Through the use of appropriate instrumentation, the parameters recorded are: a corrected or compensated value of [[bulk density]], a measure of the correction, Δr, used in making the compensation, and a [[caliper log|caliper]] [[curve]]. With the unwanted borehole effects removed, the measurement is recorded directly in terms of [[bulk density]] on a linear [[scale]]. See also [[density log]], [[spine and ribs plot|spine-and-ribs plot]], and [[ZA effect|Z/A effect]].

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