Editing Well logging (section)

====Neutron porosity====
{{See also|Formation evaluation neutron porosity}}
The neutron porosity log works by bombarding a formation with high energy [[Neutron temperature|epithermal neutrons]] that lose energy through [[elastic scattering]] to near thermal levels before being absorbed by the [[Atomic nucleus|nuclei]] of the formation atoms.  Depending on the particular type of neutron logging tool, either the [[gamma ray]] of capture, scattered thermal neutrons or scattered, higher energy epithermal neutrons are detected.<ref>{{Cite web|url=http://www.glossary.oilfield.slb.com/Display.cfm?Term=epithermal%20neutron%20porosity%20measurement|title=Schlumberger Oilfield Glossary}}</ref>  The neutron porosity log is predominantly sensitive to the quantity of [[hydrogen atom]]s in a particular formation, which generally corresponds to rock porosity.

[[Boron]] is known to cause anomalously low neutron tool count rates due to it having a high capture cross section for thermal neutron absorption.<ref>
{{cite book
  | last = Etnyre
  | first = L.M.
  | title = Finding Oil and Gas from Well Logs
  | publisher = Kluwer Academic Publishers 
  | year = 1989
  | isbn = 978-0442223090
  | page = 249 p }}</ref>   An increase in hydrogen concentration in clay minerals has a similar effect on the count rate.