5. Gamma-gamma and neutron-neutron logs

5.1 Scope and conditions of application

• Gamma-gamma (γ - γ) and neutron-neutron (N-N) induced radioactivity logs provide precise quantitative information on quantities that can be used directly by the structure designer. These are, respectively, the density and water content of the materials traversed by the borehole.

  In addition, like other logs, they contribute to geological knowledge of the terrain: nature, depth and thickness of the layers.

  Fractures are characterized by low density and high water content when they are flooded and open. When they contain another material, such as clay or sand, the density remains lower than that of the bedrock, but higher than if they were full of water, and the water content...