Z/A effect

{
  "id": "MLC-T-OAG-004195",
  "term": "Z/A effect",
  "field": "Oil and gas",
  "definition": "The dependence of the gamma-gamma density response on the ratio of atomic number to atomic mass of the formation. The tool measures electron density through Compton scattering, which equals the bulk density times twice Z/A, and Z/A is close to 0.5 for most rock-forming elements but about 1 for hydrogen. Fresh water, for example, has Z/A of about 0.555 and reads near 1.11 g/cm3 before correction, which is why the apparent density is corrected to give bulk density.",
  "subject": "Formation Evaluation",
  "url": "https://mlchart.com/terminology/oil-and-gas/z-a-effect/"
}