This is a well log used in the oil and gas industry. You might have encountered this acronym RAC in your log evaluation software or any (ASCII) log files provided by the logging company. The abreviatin stands for 'Resistivity Attenuation Borehole Corrected'. This log is very common in the industry.

This log displays readings of 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. At a higher level, this can be seen as a measure of the electromagnetic propagation resistivity. In other words, 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:

• Resistivity Attenuation Borehole and Inversion Corrected (RACV)
• Resistivity Phase Difference Borehole Corrected (RPC)
• Electromagnetic Propagation Resistivity (EPR)
• Resistivity Attenuation Compensated Borehole Corrected Long 400kHz (RACL)
• Resistivity Attenuation Borehole, Dielectric and Inversion Corrected (RACD)
• Resistivity Attenuation Compensated Borehole Corrected Long 2MHz (RACH)
• CDR Attenuation Resistivity (ATR)
• Resistivity Attenuation Borehole and Dielectric Corrected (RACE)
• Compensated Phase Shift Resistivity (PSR)
• Resistivity Phase Difference Apparent (RPA)