Dual Neutron Tool
The neutron tool essentially responds to the hydrogen content of the surrounding material. Below groundwater level the pores in the rock will be filled with water and hence the neutron – neutron log maybe used to determine porosity under suitable conditions. Note this tool uses a sealed radioactive source of neutrons.
Where the borehole is lined, it is possible to use the log in a qualitative way to identify the differing zones of relative hydrogen content.
The neutron log responds to hydrogen contained in ‘free’ water, however it also responds to water that is chemically bound within clays as shown in the example below.
Size:1300 x 38mm
2 – 5 m / min
*In lined or cased sections of boreholes these logs give qualitative information on the porosity of the material behind the linings
50 – 300mm