This is an abbreviation for a well log used in the oil and gas industry. You could find this abbreviation
TNPH in your log evaluation software or any (ASCII) log files provided by the logging company.
Thermal Neutron Porosity (Ratio Method) in Selected Lithology is the offical name for this log. This log is very common in the industry. This log can be used to evaluate the porosity as measured with a thermal neutron logging device.
Concluding, this is a measure of the porosity as measured with an neutron logging device. At a higher level, this can be seen as a measure of the apparent porosity. In other words, the initial estimate of porosity, normally from logs, not corrected for the (often large) effects of clays, gas, etc. Such estimates should only be used for qualitative interpretation of clean, gas-free intervals.
Furthermore, this can be explained by looking at the volume fraction. This is a measure of the ratio of the volumes occupied by two components, or by one component to the total volume of the system.This log usually has the unit
'Porosity'. This is the pore volume per unit gross volume. Porosity is determined from measurements on cores or interpreted from logs.
Data for this log is produced by a tool that uses a neutron logging technique and can be used to investigate the porosity of the formation. Similar logs are listed below:
