This is a log of measurements along a well bore (a well-log). You could have found the code
SDPB_HR in your log evaluation software or your corporate datastores. The official name for this log is
'APS Slowing Down Porosity - Borehole Corrected - High Resolution'. This log is not often acquired after (or during) drilling a well. Use this log to investigate the porosity as measured with an epithermal neutron 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. This can be explained as being 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 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: