Study on the Measurement Range and Accuracy of Russian ЭКOC-31-7 Through Casing Resistivity Logging Tool

Through casing resistivity logging tool detects the weak signals of nV level leaking to the formation through the metal casing.Due to the ability of the weak signal detection and data processing are different for different tools,the range and accuracy of measurement are also different.The range and error of measurement of the Russian ЭКOC-31-7 tool are investigated with theory and laboratory test.The results show that the measurement range of Russian ЭКOC-31-7 tool is 1~200 Ω·m,the average relative error is less than ± 10%.When resistivity gradually rises,the maximum relative error of the tool also gradually increases.The measurement accuracy of the tool is relatively high for low resistivity formation when the resistivity is less than 60 Ω·m;otherwise the measurement accuracy of the tool is relatively low.Measurement accuracy of the tool can be improved by calculating the average resistivity through repeated measurements.This study has guiding significance for log operations and data interpretation of the Russian ЭКOC-31-7 tool.