Anhydrite as a Donwhole Log Calibrator


W.D.M Smith, Dresser Atlas



Massive anhydrite beds can be used successfully to calibrate well logs downhole or after logging. Density logs, acoustic travel time logs and induct- ion logs can be adjusted to improve log readings. In the Rainbow-Zama area of Northern Alberta, log values of anhydrite density should average 2.91 9/cc, acoustic travel times should be fixed at an average arbitrary value (51 micro- seconds per foot) for consistency and maximum conductivity in thick anhydrite beds should be 3 millimhos per meter or less. These particular anhydrites ex- hibit low count rates on the Neutron Lifetime Log.