This is a well log used in the oil and gas industry. The code
NPHS is a unique identifier to recognize this particular log and can be found in any (ASCII) log files provided by the logging company. The official name for this log is
'Neutron Porosity Sandstone'. The business value of this log is often deamed high. Use this log to investigate the porosity derived from a neutron logging measurement, assuming that the rock matrix material is quartz.
Simply said, this is a log that describes the porosity as measured with an neutron logging device. In general this log therefore displays units of the apparent porosity. Better said, 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.
In general this log thus reflects units of the volume fraction. This can be explained as being 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: