Active standoff compensation in measurements with oil-based mud resistivity imaging devices

摘要

Disclosed is an apparatus for estimating a property of an earth formation penetrated by a borehole having a substantially non-conducting liquid. The apparatus includes: a downhole tool having a transmitter electrode configured to convey an electric current into the earth formation. A measurement electrode is configured to receive the electric current from the earth formation, wherein the electric current bridges as least one of a first gap between the transmitter electrode and the formation and a second gap between the measurement electrode and the formation. A compensating circuit coupling the transmitter electrode to the measurement electrode is configured to reduce a reactive component of a total current received by the measurement electrode. A receiver coupled to the measurement electrode is configured to measure the total current to estimate the property.