This is the name of a log measured along a well bore (a well-log). The acronym
CBP4_SL is a unique identifier to recognize this particular log and can be encountered in your log evaluation software or your corporate datastores. The official name for this log is
'CMR Bin Porosity 4 - Station Log'. This log is not often acquired after (or during) drilling a well. This log helps to evaluate the contribution of porosity from a given "bin" (with certain characteristics) to the total porosity; e.g., in nuclear magnetic resonance data processing, the "bins" typically correspond to different pore size ranges.
In general this log thus reflects units 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.
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 nmr logging technique and can be used to investigate the porosity of the formation. Similar logs are listed below: