Patent ID: 8862406

Claim:
An apparatus configured to evaluate an earth formation penetrated by a borehole having a non-conducting fluid therein, the apparatus comprising: a carrier; a logging tool disposed on the carrier, the logging tool comprising: a pad body; at least one transmitter disposed on the pad body; and at least one measure electrode electrically isolated from the at least one transmitter and a body of the logging tool; wherein a ratio between (i) an area of the at least one transmitter and (ii) an area of the at least one measure electrode and a ratio between (i) an impedance between the pad body and the body of the logging tool and (ii) an impedance between the at least one transmitter and the body of the logging tool are both sufficient to reduce a current leakage from the earth formation to the body of the logging tool; and at least one processor configured to estimate a resistivity parameter of the earth formation using an impedance determined from a current at the at least one measure electrode and a potential of the at least one transmitter.