Patent ID: 8115490

Claim:
A method of estimating a property of an earth formation penetrated by a borehole, the method comprising: disposing into the borehole a sensor comprising a plurality of return electrodes and at least one transmitter electrode disposed in a concentric arrangement; injecting a first current, I 1 , of a first frequency, f 1 , into the formation by applying an alternating current (AC) voltage between first selected ones of the plurality of return electrodes and the at least one transmitter electrode; injecting a second current, I 2 , of a second frequency, f 2 , into the formation by applying an alternating current (AC) voltage between second selected ones of the plurality of return electrodes and the at least one transmitter electrode; measuring effective impedance, Z e , for each of the currents; and estimating the property using the measurements of the effective impedance, Z e , for each of the currents; wherein the estimating compensates for an influence of standoff distances of the sensor on the measurements.