This is an abbreviation for a well log used in the oil and gas industry. The code
RAAL is a unique identifier to recognize this particular log and can be found in any (ASCII) log files provided by the logging company.
Resistivity Attenuation Compensated Apparent Long 400kHz is the full name for this log. This log is not used too often in the industry. This log helps to evaluate the formation resistivity as measured by the attenuation of a high frequency (hundreds of KHz to several MHz) electromagnetic wave; these measurements are typically deeper than measurements based on phase shift, but their vertical resolution is less sharp and they often cannot be used reliably in high-resistivity formations.
In general this log thus reflects units of the electromagnetic propagation resistivity. Better said, the formation resistivity as measured by the attenuation or phase shift of a high frequency electromagnetic wave; the frequency range for these measurements is higher than that of induction measurements, typically hundreds of KHz to several MHz, and over 1 GHz in the case of the Schlumberger EPT tool.This log usually has the unit
'Resistivity'. This is the property of a material which resists the flow of electrical current. The ratio of electric-field intensity to current density. The reciprocal of conductivity.
Data for this log is produced by a tool that uses a electromagnetic logging technique and can be used to investigate the resistivity of the formation. Similar logs are listed below: