Patent ID: 7928733

Claim:
A method of estimating a property of an earth formation traversed 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 first 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 using a predetermined relationship between at least one of the effective impedance, Z e , and standoff, to estimate the standoff between the sensor and the borehole.