Changes

===Overlay presentation===

===Overlay presentation===

Manual crossplotting is tedious. A much faster way to visualize rock type is directly from the overlay presentation in which both neutron and density logs are superimposed in the same log track. To do this, a compatible scale must be used so that the porosity components of both logs exactly overlay. Then any offset (or residual) between the two logs is attributable to lithology or to the presence of gas.

Manual crossplotting is tedious. A much faster way to visualize rock type is directly from the overlay presentation in which both neutron and density logs are superimposed in the same log track. To do this, a compatible scale must be used so that the porosity components of both logs exactly overlay. Then any [[offset]] (or residual) between the two logs is attributable to lithology or to the presence of gas.

Both tools are generally calibrated in limestone units, so the compatible scale is defined for freshwater-limestone systems, with theoretical limits as follows:

Both tools are generally calibrated in limestone units, so the compatible scale is defined for freshwater-limestone systems, with theoretical limits as follows: