Resistivity Behind Casing Toolâ€“ RBC measures deep true formation resistivity behind steel casing to detect and evaluate bypassed hydrocarbons. Saturations determined from resistivity measurements are considered better than the data acquired by pulsed neutron logging tools due to the fact that the depth of investigation is significantly higher than standard nuclear measurements. The depth of investigation is from 7 to 32 ft, depending on well conditions.
The RBC is a stationary tool. The electrical current output from the probes moves from above and below in the steel casing in turn in time through current electrodes. The majority of the current travels through the casing column while the remaining â€œleaked currentâ€ enters the formation. The leaked current is measured and processed to determine the formation resistivity with the casing column influence removed.