Formation resistivity imager with reduced leakage to mandrel

摘要

A method of estimating a parameter of a formation contacting a borehole with an instrument that includes a mandrel and a pad includes providing a measurement voltage to the pad; applying a biasing voltage to the mandrel while the measurement voltage is applied to the pad; measuring a received current during at least a portion of time the measurement voltage is provided; and estimating the parameter based on the received current.