METHOD OF LEAKAGE CURRENT AND BOREHOLE ENVIRONMENT CORRECTION FOR OIL BASED MUD IMAGER

摘要

A correction method for resistivity measurements of formation surrounding a borehole includes deploying a logging tool in the borehole and having a standoff in between the logging tool and the wall of the borehole, measuring a total current entering into the pair of current electrodes, computing a leakage current in the sensor pad caused by an internal capacitive impedance between the pair of current electrodes and the main body of the sensor pad, computing a measuring current to enter into the formation for the resistivity measurements by subtracting the leakage current from the total current, computing an external capacitive impedance between the current electrodes and the formation, utilizing a pre-built chart to obtain a geometric factor based on the external capacitive impedance, and computing resistivity of the formation based on the geometric factor.

主权项

1. A correction method for resistivity measurements of formation surrounding a borehole comprising:
deploying a logging tool in the borehole and having a standoff in between the logging tool and the wall of the borehole; wherein the logging tool including a sensor pad embedded with a pair of current electrodes and a pair of voltage electrodes and a measurement circuit; wherein the current electrodes and voltage electrodes being insulated from the main body of the sensor pad; and wherein the measurement circuit providing source voltages to the pair of current electrodes; measuring a total current entering into the pair of current electrodes; computing a leakage current in the sensor pad caused by an internal capacitive impedance between the pair of current electrodes and the main body of the sensor pad; computing a measuring current to enter into the formation for the resistivity measurements by subtracting the leakage current from the total current; computing an external capacitive impedance between the current electrodes and the formation; utilizing a pre-built chart to obtain a geometric factor based on the external capacitive impedance; and computing resistivity of the formation based on the geometric factor.