This log provides a continuous measure of the bulk density of a formation, and is related to the density of the rock (a mix of the solid matrix of the rock and the fluid it contains in its porosity). Thus the bulk density represents the density of the minerals forming the rock being measured and the liquid it contains (porosity). If the lithology of a formation is know, the density log can be used to determine its porosity. Uncompacted shales have lower density than sandstone of same porosity, making this log a good indicator of grain size.
Density log values (in gm/cm3) for some rock types are: sandstone with no porosity 2.65g/cm3, sandstone with with 10% porosity 2.49g/cm3, limestone with no porosity 2.71g/cm3, limestone with with 10% porosity 2.54g/cm3, dolomite with no porosity 2.87g/cm3, dolomite with with 10% porosity 2.68g/cm3, anhydrite with no porosity 2.96g/cm3, halite with no porosity 2.16g/cm3.
A good source of further information on well logs, one that this web site has used, is Malcolm Rider, 1996, "The geological interpretation of well logs", 2nd edition, Gulf Publishing Company, Houston p. 280 ISBN 0-88415-354-1.
